zcache: page cache compression support
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From: Dan Magenheimer on 22 Jul 2010 16:00 > From: Greg KH [mailto:greg(a)kroah.com] > Sent: Thursday, July 22, 2010 1:15 PM > To: Nitin Gupta > Cc: Pekka Enberg; Hugh Dickins; Andrew Morton; Dan Magenheimer; Rik van > Riel; Avi Kivity; Christoph Hellwig; Minchan Kim; Konrad Rzeszutek > Wilk; linux-mm; linux-kernel > Subject: Re: [PATCH 0/8] zcache: page cache compression support > > On Fri, Jul 16, 2010 at 06:07:42PM +0530, Nitin Gupta wrote: > > Frequently accessed filesystem data is stored in memory to reduce > access to > > (much) slower backing disks. Under memory pressure, these pages are > freed and > > when needed again, they have to be read from disks again. When > combined working > > set of all running application exceeds amount of physical RAM, we get > extereme > > slowdown as reading a page from disk can take time in order of > milliseconds. > > <snip> > > Given that there were a lot of comments and changes for this series, > can > you resend them with your updates so I can then apply them if they are > acceptable to everyone? > > thanks, > greg k-h Hi Greg -- Nitin's zcache code is dependent on the cleancache series: http://lkml.org/lkml/2010/6/21/411 The cleancache series has not changed since V3 (other than fixing a couple of documentation typos) and didn't receive any comments other than Christoph's concern that there weren't any users... which I think has been since addressed with the posting of the Xen tmem driver code and Nitin's zcache. If you are ready to apply the cleancache series, great! If not, please let me know next steps so cleancache isn't an impediment for applying the zcache series. Thanks, Dan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Greg KH on 22 Jul 2010 17:20 On Thu, Jul 22, 2010 at 12:54:57PM -0700, Dan Magenheimer wrote: > > From: Greg KH [mailto:greg(a)kroah.com] > > Sent: Thursday, July 22, 2010 1:15 PM > > To: Nitin Gupta > > Cc: Pekka Enberg; Hugh Dickins; Andrew Morton; Dan Magenheimer; Rik van > > Riel; Avi Kivity; Christoph Hellwig; Minchan Kim; Konrad Rzeszutek > > Wilk; linux-mm; linux-kernel > > Subject: Re: [PATCH 0/8] zcache: page cache compression support > > > > On Fri, Jul 16, 2010 at 06:07:42PM +0530, Nitin Gupta wrote: > > > Frequently accessed filesystem data is stored in memory to reduce > > access to > > > (much) slower backing disks. Under memory pressure, these pages are > > freed and > > > when needed again, they have to be read from disks again. When > > combined working > > > set of all running application exceeds amount of physical RAM, we get > > extereme > > > slowdown as reading a page from disk can take time in order of > > milliseconds. > > > > <snip> > > > > Given that there were a lot of comments and changes for this series, > > can > > you resend them with your updates so I can then apply them if they are > > acceptable to everyone? > > > > thanks, > > greg k-h > > Hi Greg -- > > Nitin's zcache code is dependent on the cleancache series: > http://lkml.org/lkml/2010/6/21/411 Ah, I didn't realize that. Hm, that makes it something that I can't take until that code is upstream, sorry. > The cleancache series has not changed since V3 (other than > fixing a couple of documentation typos) and didn't receive any > comments other than Christoph's concern that there weren't > any users... which I think has been since addressed with the > posting of the Xen tmem driver code and Nitin's zcache. > > If you are ready to apply the cleancache series, great! > If not, please let me know next steps so cleancache isn't > an impediment for applying the zcache series. I don't know, work with the kernel developers to resolve the issues they pointed out in the cleancache code and when it goes in, then I can take these patches. good luck, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: caiqian on 23 Jul 2010 13:40 ----- "Nitin Gupta" <ngupta(a)vflare.org> wrote: > Frequently accessed filesystem data is stored in memory to reduce > access to > (much) slower backing disks. Under memory pressure, these pages are > freed and > when needed again, they have to be read from disks again. When > combined working > set of all running application exceeds amount of physical RAM, we get > extereme > slowdown as reading a page from disk can take time in order of > milliseconds. > > Memory compression increases effective memory size and allows more > pages to > stay in RAM. Since de/compressing memory pages is several orders of > magnitude > faster than disk I/O, this can provide signifant performance gains for > many > workloads. Also, with multi-cores becoming common, benefits of reduced > disk I/O > should easily outweigh the problem of increased CPU usage. > > It is implemented as a "backend" for cleancache_ops [1] which > provides > callbacks for events such as when a page is to be removed from the > page cache > and when it is required again. We use them to implement a 'second > chance' cache > for these evicted page cache pages by compressing and storing them in > memory > itself. > > We only keep pages that compress to PAGE_SIZE/2 or less. Compressed > chunks are > stored using xvmalloc memory allocator which is already being used by > zram > driver for the same purpose. Zero-filled pages are checked and no > memory is > allocated for them. > > A separate "pool" is created for each mount instance for a > cleancache-aware > filesystem. Each incoming page is identified with <pool_id, inode_no, > index> > where inode_no identifies file within the filesystem corresponding to > pool_id > and index is offset of the page within this inode. Within a pool, > inodes are > maintained in an rb-tree and each of its nodes points to a separate > radix-tree > which maintains list of pages within that inode. > > While compression reduces disk I/O, it also reduces the space > available for > normal (uncompressed) page cache. This can result in more frequent > page cache > reclaim and thus higher CPU overhead. Thus, it's important to maintain > good hit > rate for compressed cache or increased CPU overhead can nullify any > other > benefits. This requires adaptive (compressed) cache resizing and page > replacement policies that can maintain optimal cache size and quickly > reclaim > unused compressed chunks. This work is yet to be done. However, in the > current > state, it allows manually resizing cache size using (per-pool) sysfs > node > 'memlimit' which in turn frees any excess pages *sigh* randomly. > > Finally, it uses percpu stats and compression buffers to allow better > performance on multi-cores. Still, there are known bottlenecks like a > single > xvmalloc mempool per zcache pool and few others. I will work on this > when I > start with profiling. > > * Performance numbers: > - Tested using iozone filesystem benchmark > - 4 CPUs, 1G RAM > - Read performance gain: ~2.5X > - Random read performance gain: ~3X > - In general, performance gains for every kind of I/O > > Test details with graphs can be found here: > http://code.google.com/p/compcache/wiki/zcacheIOzone > > If I can get some help with testing, it would be intersting to find > its > effect in more real-life workloads. In particular, I'm intersted in > finding > out its effect in KVM virtualization case where it can potentially > allow > running more number of VMs per-host for a given amount of RAM. With > zcache > enabled, VMs can be assigned much smaller amount of memory since host > can now > hold bulk of page-cache pages, allowing VMs to maintain similar level > of > performance while a greater number of them can be hosted. > > * How to test: > All patches are against 2.6.35-rc5: > > - First, apply all prerequisite patches here: > http://compcache.googlecode.com/hg/sub-projects/zcache_base_patches > > - Then apply this patch series; also uploaded here: > http://compcache.googlecode.com/hg/sub-projects/zcache_patches > > > Nitin Gupta (8): > Allow sharing xvmalloc for zram and zcache > Basic zcache functionality > Create sysfs nodes and export basic statistics > Shrink zcache based on memlimit > Eliminate zero-filled pages > Compress pages using LZO > Use xvmalloc to store compressed chunks > Document sysfs entries > > Documentation/ABI/testing/sysfs-kernel-mm-zcache | 53 + > drivers/staging/Makefile | 2 + > drivers/staging/zram/Kconfig | 22 + > drivers/staging/zram/Makefile | 5 +- > drivers/staging/zram/xvmalloc.c | 8 + > drivers/staging/zram/zcache_drv.c | 1312 > ++++++++++++++++++++++ > drivers/staging/zram/zcache_drv.h | 90 ++ > 7 files changed, 1491 insertions(+), 1 deletions(-) > create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-zcache > create mode 100644 drivers/staging/zram/zcache_drv.c > create mode 100644 drivers/staging/zram/zcache_drv.h By tested those patches on the top of the linus tree at this commit d0c6f6258478e1dba532bf7c28e2cd6e1047d3a4, the OOM was trigger even though there looked like still lots of swap. # free -m total used free shared buffers cached Mem: 852 379 473 0 3 15 -/+ buffers/cache: 359 492 Swap: 2015 14 2001 # ./usemem 1024 0: Mallocing 32 megabytes 1: Mallocing 32 megabytes 2: Mallocing 32 megabytes 3: Mallocing 32 megabytes 4: Mallocing 32 megabytes 5: Mallocing 32 megabytes 6: Mallocing 32 megabytes 7: Mallocing 32 megabytes 8: Mallocing 32 megabytes 9: Mallocing 32 megabytes 10: Mallocing 32 megabytes 11: Mallocing 32 megabytes 12: Mallocing 32 megabytes 13: Mallocing 32 megabytes 14: Mallocing 32 megabytes 15: Mallocing 32 megabytes Connection to 192.168.122.193 closed. usemem invoked oom-killer: gfp_mask=0x280da, order=0, oom_adj=0 usemem cpuset=/ mems_allowed=0 Pid: 1829, comm: usemem Not tainted 2.6.35-rc5+ #5 Call Trace: [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 [<ffffffff81108520>] dump_header+0x70/0x190 [<ffffffff811086c1>] oom_kill_process+0x81/0x180 [<ffffffff81108c08>] __out_of_memory+0x58/0xd0 [<ffffffff81108ddc>] ? out_of_memory+0x15c/0x1f0 [<ffffffff81108d8f>] out_of_memory+0x10f/0x1f0 [<ffffffff8110cc7f>] __alloc_pages_nodemask+0x7af/0x7c0 [<ffffffff81140a69>] alloc_page_vma+0x89/0x140 [<ffffffff81125f76>] handle_mm_fault+0x6d6/0x990 [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 [<ffffffff81121afd>] ? follow_page+0x19d/0x350 [<ffffffff8112639c>] __get_user_pages+0x16c/0x480 [<ffffffff810127c9>] ? sched_clock+0x9/0x10 [<ffffffff811276ef>] __mlock_vma_pages_range+0xef/0x1f0 [<ffffffff81127f01>] mlock_vma_pages_range+0x91/0xa0 [<ffffffff8112ad57>] mmap_region+0x307/0x5b0 [<ffffffff8112b354>] do_mmap_pgoff+0x354/0x3a0 [<ffffffff8112b3fc>] ? sys_mmap_pgoff+0x5c/0x200 [<ffffffff8112b41a>] sys_mmap_pgoff+0x7a/0x200 [<ffffffff814e02f2>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff8100fa09>] sys_mmap+0x29/0x30 [<ffffffff8100b032>] system_call_fastpath+0x16/0x1b Mem-Info: Node 0 DMA per-cpu: CPU 0: hi: 0, btch: 1 usd: 0 CPU 1: hi: 0, btch: 1 usd: 0 Node 0 DMA32 per-cpu: CPU 0: hi: 186, btch: 31 usd: 140 CPU 1: hi: 186, btch: 31 usd: 47 active_anon:128 inactive_anon:140 isolated_anon:0 active_file:0 inactive_file:9 isolated_file:0 unevictable:126855 dirty:0 writeback:125 unstable:0 free:1996 slab_reclaimable:4445 slab_unreclaimable:23646 mapped:923 shmem:7 pagetables:778 bounce:0 Node 0 DMA free:4032kB min:60kB low:72kB high:88kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:11896kB isolated(anon):0kB isolated(file):0kB present:15756kB mlocked:11896kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:24kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes lowmem_reserve[]: 0 994 994 994 Node 0 DMA32 free:3952kB min:4000kB low:5000kB high:6000kB active_anon:512kB inactive_anon:560kB active_file:0kB inactive_file:36kB unevictable:495524kB isolated(anon):0kB isolated(file):0kB present:1018060kB mlocked:495524kB dirty:0kB writeback:500kB mapped:3692kB shmem:28kB slab_reclaimable:17780kB slab_unreclaimable:94584kB kernel_stack:1296kB pagetables:3088kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1726 all_unreclaimable? yes lowmem_reserve[]: 0 0 0 0 Node 0 DMA: 0*4kB 2*8kB 1*16kB 1*32kB 2*64kB 2*128kB 2*256kB 0*512kB 1*1024kB 1*2048kB 0*4096kB = 4032kB Node 0 DMA32: 476*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 1*2048kB 0*4096kB = 3952kB 1146 total pagecache pages 215 pages in swap cache Swap cache stats: add 19633, delete 19418, find 941/1333 Free swap = 2051080kB Total swap = 2064380kB 262138 pages RAM 43914 pages reserved 4832 pages shared 155665 pages non-shared Out of memory: kill process 1727 (console-kit-dae) score 1027939 or a child Killed process 1727 (console-kit-dae) vsz:4111756kB, anon-rss:0kB, file-rss:600kB console-kit-dae invoked oom-killer: gfp_mask=0xd0, order=0, oom_adj=0 console-kit-dae cpuset=/ mems_allowed=0 Pid: 1752, comm: console-kit-dae Not tainted 2.6.35-rc5+ #5 Call Trace: [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 [<ffffffff81108520>] dump_header+0x70/0x190 [<ffffffff811086c1>] oom_kill_process+0x81/0x180 [<ffffffff81108c08>] __out_of_memory+0x58/0xd0 [<ffffffff81108ddc>] ? out_of_memory+0x15c/0x1f0 [<ffffffff81108d8f>] out_of_memory+0x10f/0x1f0 [<ffffffff8110cc7f>] __alloc_pages_nodemask+0x7af/0x7c0 [<ffffffff8114522e>] kmem_getpages+0x6e/0x180 [<ffffffff81147d79>] fallback_alloc+0x1c9/0x2b0 [<ffffffff81147602>] ? cache_grow+0x4b2/0x520 [<ffffffff81147a5b>] ____cache_alloc_node+0xab/0x200 [<ffffffff810d55d5>] ? taskstats_exit+0x305/0x3b0 [<ffffffff8114862b>] kmem_cache_alloc+0x1fb/0x290 [<ffffffff810d55d5>] taskstats_exit+0x305/0x3b0 [<ffffffff81063a4b>] do_exit+0x12b/0x890 [<ffffffff810924fd>] ? trace_hardirqs_off+0xd/0x10 [<ffffffff8108641f>] ? cpu_clock+0x6f/0x80 [<ffffffff81095cbd>] ? lock_release_holdtime+0x3d/0x190 [<ffffffff814e1010>] ? _raw_spin_unlock_irq+0x30/0x40 [<ffffffff8106420e>] do_group_exit+0x5e/0xd0 [<ffffffff81075b54>] get_signal_to_deliver+0x2d4/0x490 [<ffffffff811ea6ad>] ? inode_has_perm+0x7d/0xf0 [<ffffffff8100a2e5>] do_signal+0x75/0x7b0 [<ffffffff81169d2d>] ? vfs_ioctl+0x3d/0xf0 [<ffffffff8116a394>] ? do_vfs_ioctl+0x84/0x570 [<ffffffff8100aa85>] do_notify_resume+0x65/0x80 [<ffffffff814e02f2>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff8100b381>] int_signal+0x12/0x17 Mem-Info: Node 0 DMA per-cpu: CPU 0: hi: 0, btch: 1 usd: 0 CPU 1: hi: 0, btch: 1 usd: 0 Node 0 DMA32 per-cpu: CPU 0: hi: 186, btch: 31 usd: 151 CPU 1: hi: 186, btch: 31 usd: 61 active_anon:128 inactive_anon:165 isolated_anon:0 active_file:0 inactive_file:9 isolated_file:0 unevictable:126855 dirty:0 writeback:25 unstable:0 free:1965 slab_reclaimable:4445 slab_unreclaimable:23646 mapped:923 shmem:7 pagetables:778 bounce:0 Node 0 DMA free:4032kB min:60kB low:72kB high:88kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:11896kB isolated(anon):0kB isolated(file):0kB present:15756kB mlocked:11896kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:24kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes lowmem_reserve[]: 0 994 994 994 Node 0 DMA32 free:3828kB min:4000kB low:5000kB high:6000kB active_anon:512kB inactive_anon:660kB active_file:0kB inactive_file:36kB unevictable:495524kB isolated(anon):0kB isolated(file):0kB present:1018060kB mlocked:495524kB dirty:0kB writeback:100kB mapped:3692kB shmem:28kB slab_reclaimable:17780kB slab_unreclaimable:94584kB kernel_stack:1296kB pagetables:3088kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1726 all_unreclaimable? yes lowmem_reserve[]: 0 0 0 0 Node 0 DMA: 0*4kB 2*8kB 1*16kB 1*32kB 2*64kB 2*128kB 2*256kB 0*512kB 1*1024kB 1*2048kB 0*4096kB = 4032kB Node 0 DMA32: 445*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 1*2048kB 0*4096kB = 3828kB 1146 total pagecache pages 230 pages in swap cache Swap cache stats: add 19649, delete 19419, find 942/1336 Free swap = 2051084kB Total swap = 2064380kB 262138 pages RAM 43914 pages reserved 4818 pages shared 155685 pages non-shared Out of memory: kill process 1806 (sshd) score 9474 or a child Killed process 1810 (bash) vsz:108384kB, anon-rss:0kB, file-rss:656kB console-kit-dae invoked oom-killer: gfp_mask=0xd0, order=0, oom_adj=0 console-kit-dae cpuset=/ mems_allowed=0 Pid: 1752, comm: console-kit-dae Not tainted 2.6.35-rc5+ #5 Call Trace: [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 [<ffffffff81108520>] dump_header+0x70/0x190 [<ffffffff811086c1>] oom_kill_process+0x81/0x180 [<ffffffff81108c08>] __out_of_memory+0x58/0xd0 [<ffffffff81108ddc>] ? out_of_memory+0x15c/0x1f0 [<ffffffff81108d8f>] out_of_memory+0x10f/0x1f0 [<ffffffff8110cc7f>] __alloc_pages_nodemask+0x7af/0x7c0 [<ffffffff8114522e>] kmem_getpages+0x6e/0x180 [<ffffffff81147d79>] fallback_alloc+0x1c9/0x2b0 [<ffffffff81147602>] ? cache_grow+0x4b2/0x520 [<ffffffff81147a5b>] ____cache_alloc_node+0xab/0x200 [<ffffffff810d55d5>] ? taskstats_exit+0x305/0x3b0 [<ffffffff8114862b>] kmem_cache_alloc+0x1fb/0x290 [<ffffffff810d55d5>] taskstats_exit+0x305/0x3b0 [<ffffffff81063a4b>] do_exit+0x12b/0x890 [<ffffffff810924fd>] ? trace_hardirqs_off+0xd/0x10 [<ffffffff8108641f>] ? cpu_clock+0x6f/0x80 [<ffffffff81095cbd>] ? lock_release_holdtime+0x3d/0x190 [<ffffffff814e1010>] ? _raw_spin_unlock_irq+0x30/0x40 [<ffffffff8106420e>] do_group_exit+0x5e/0xd0 [<ffffffff81075b54>] get_signal_to_deliver+0x2d4/0x490 [<ffffffff811ea6ad>] ? inode_has_perm+0x7d/0xf0 [<ffffffff8100a2e5>] do_signal+0x75/0x7b0 [<ffffffff81169d2d>] ? vfs_ioctl+0x3d/0xf0 [<ffffffff8116a394>] ? do_vfs_ioctl+0x84/0x570 [<ffffffff8100aa85>] do_notify_resume+0x65/0x80 [<ffffffff814e02f2>] ? trace_hardirqs_on_thunk+0x3a/0x3f [<ffffffff8100b381>] int_signal+0x12/0x17 Mem-Info: Node 0 DMA per-cpu: CPU 0: hi: 0, btch: 1 usd: 0 CPU 1: hi: 0, btch: 1 usd: 0 Node 0 DMA32 per-cpu: CPU 0: hi: 186, btch: 31 usd: 119 CPU 1: hi: 186, btch: 31 usd: 73 active_anon:50 inactive_anon:175 isolated_anon:0 active_file:0 inactive_file:9 isolated_file:0 unevictable:126855 dirty:0 writeback:25 unstable:0 free:1996 slab_reclaimable:4445 slab_unreclaimable:23663 mapped:923 shmem:7 pagetables:778 bounce:0 Node 0 DMA free:4032kB min:60kB low:72kB high:88kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:11896kB isolated(anon):0kB isolated(file):0kB present:15756kB mlocked:11896kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:24kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes lowmem_reserve[]: 0 994 994 994 Node 0 DMA32 free:3952kB min:4000kB low:5000kB high:6000kB active_anon:200kB inactive_anon:700kB active_file:0kB inactive_file:36kB unevictable:495524kB isolated(anon):0kB isolated(file):0kB present:1018060kB mlocked:495524kB dirty:0kB writeback:100kB mapped:3692kB shmem:28kB slab_reclaimable:17780kB slab_unreclaimable:94652kB kernel_stack:1296kB pagetables:3088kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1536 all_unreclaimable? yes lowmem_reserve[]: 0 0 0 0 Node 0 DMA: 0*4kB 2*8kB 1*16kB 1*32kB 2*64kB 2*128kB 2*256kB 0*512kB 1*1024kB 1*2048kB 0*4096kB = 4032kB Node 0 DMA32: 470*4kB 3*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 1*2048kB 0*4096kB = 3952kB 1146 total pagecache pages 221 pages in swap cache Swap cache stats: add 19848, delete 19627, find 970/1386 Free swap = 2051428kB Total swap = 2064380kB 262138 pages RAM 43914 pages reserved 4669 pages shared 155659 pages non-shared Out of memory: kill process 1829 (usemem) score 8253 or a child Killed process 1829 (usemem) vsz:528224kB, anon-rss:502468kB, file-rss:376kB # cat usemem.c # cat usemem.c #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/mman.h> #define CHUNKS 32 int main(int argc, char *argv[]) { mlockall(MCL_FUTURE); unsigned long mb; char *buf[CHUNKS]; int i; if (argc < 2) { fprintf(stderr, "usage: usemem megabytes\n"); exit(1); } mb = strtoul(argv[1], NULL, 0); for (i = 0; i < CHUNKS; i++) { fprintf(stderr, "%d: Mallocing %lu megabytes\n", i, mb/CHUNKS); buf[i] = (char *)malloc(mb/CHUNKS * 1024L * 1024L); if (!buf[i]) { fprintf(stderr, "malloc failure\n"); exit(1); } } for (i = 0; i < CHUNKS; i++) { fprintf(stderr, "%d: Zeroing %lu megabytes at %p\n", i, mb/CHUNKS, buf[i]); memset(buf[i], 0, mb/CHUNKS * 1024L * 1024L); } exit(0); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: CAI Qian on 23 Jul 2010 13:50 ----- caiqian(a)redhat.com wrote: > ----- "Nitin Gupta" <ngupta(a)vflare.org> wrote: > > > Frequently accessed filesystem data is stored in memory to reduce > > access to > > (much) slower backing disks. Under memory pressure, these pages are > > freed and > > when needed again, they have to be read from disks again. When > > combined working > > set of all running application exceeds amount of physical RAM, we > get > > extereme > > slowdown as reading a page from disk can take time in order of > > milliseconds. > > > > Memory compression increases effective memory size and allows more > > pages to > > stay in RAM. Since de/compressing memory pages is several orders of > > magnitude > > faster than disk I/O, this can provide signifant performance gains > for > > many > > workloads. Also, with multi-cores becoming common, benefits of > reduced > > disk I/O > > should easily outweigh the problem of increased CPU usage. > > > > It is implemented as a "backend" for cleancache_ops [1] which > > provides > > callbacks for events such as when a page is to be removed from the > > page cache > > and when it is required again. We use them to implement a 'second > > chance' cache > > for these evicted page cache pages by compressing and storing them > in > > memory > > itself. > > > > We only keep pages that compress to PAGE_SIZE/2 or less. Compressed > > chunks are > > stored using xvmalloc memory allocator which is already being used > by > > zram > > driver for the same purpose. Zero-filled pages are checked and no > > memory is > > allocated for them. > > > > A separate "pool" is created for each mount instance for a > > cleancache-aware > > filesystem. Each incoming page is identified with <pool_id, > inode_no, > > index> > > where inode_no identifies file within the filesystem corresponding > to > > pool_id > > and index is offset of the page within this inode. Within a pool, > > inodes are > > maintained in an rb-tree and each of its nodes points to a separate > > radix-tree > > which maintains list of pages within that inode. > > > > While compression reduces disk I/O, it also reduces the space > > available for > > normal (uncompressed) page cache. This can result in more frequent > > page cache > > reclaim and thus higher CPU overhead. Thus, it's important to > maintain > > good hit > > rate for compressed cache or increased CPU overhead can nullify any > > other > > benefits. This requires adaptive (compressed) cache resizing and > page > > replacement policies that can maintain optimal cache size and > quickly > > reclaim > > unused compressed chunks. This work is yet to be done. However, in > the > > current > > state, it allows manually resizing cache size using (per-pool) > sysfs > > node > > 'memlimit' which in turn frees any excess pages *sigh* randomly. > > > > Finally, it uses percpu stats and compression buffers to allow > better > > performance on multi-cores. Still, there are known bottlenecks like > a > > single > > xvmalloc mempool per zcache pool and few others. I will work on > this > > when I > > start with profiling. > > > > * Performance numbers: > > - Tested using iozone filesystem benchmark > > - 4 CPUs, 1G RAM > > - Read performance gain: ~2.5X > > - Random read performance gain: ~3X > > - In general, performance gains for every kind of I/O > > > > Test details with graphs can be found here: > > http://code.google.com/p/compcache/wiki/zcacheIOzone > > > > If I can get some help with testing, it would be intersting to find > > its > > effect in more real-life workloads. In particular, I'm intersted in > > finding > > out its effect in KVM virtualization case where it can potentially > > allow > > running more number of VMs per-host for a given amount of RAM. With > > zcache > > enabled, VMs can be assigned much smaller amount of memory since > host > > can now > > hold bulk of page-cache pages, allowing VMs to maintain similar > level > > of > > performance while a greater number of them can be hosted. > > > > * How to test: > > All patches are against 2.6.35-rc5: > > > > - First, apply all prerequisite patches here: > > http://compcache.googlecode.com/hg/sub-projects/zcache_base_patches > > > > - Then apply this patch series; also uploaded here: > > http://compcache.googlecode.com/hg/sub-projects/zcache_patches > > > > > > Nitin Gupta (8): > > Allow sharing xvmalloc for zram and zcache > > Basic zcache functionality > > Create sysfs nodes and export basic statistics > > Shrink zcache based on memlimit > > Eliminate zero-filled pages > > Compress pages using LZO > > Use xvmalloc to store compressed chunks > > Document sysfs entries > > > > Documentation/ABI/testing/sysfs-kernel-mm-zcache | 53 + > > drivers/staging/Makefile | 2 + > > drivers/staging/zram/Kconfig | 22 + > > drivers/staging/zram/Makefile | 5 +- > > drivers/staging/zram/xvmalloc.c | 8 + > > drivers/staging/zram/zcache_drv.c | 1312 > > ++++++++++++++++++++++ > > drivers/staging/zram/zcache_drv.h | 90 ++ > > 7 files changed, 1491 insertions(+), 1 deletions(-) > > create mode 100644 > Documentation/ABI/testing/sysfs-kernel-mm-zcache > > create mode 100644 drivers/staging/zram/zcache_drv.c > > create mode 100644 drivers/staging/zram/zcache_drv.h > By tested those patches on the top of the linus tree at this commit > d0c6f6258478e1dba532bf7c28e2cd6e1047d3a4, the OOM was trigger even > though there looked like still lots of swap. > > # free -m > total used free shared buffers > cached > Mem: 852 379 473 0 3 > 15 > -/+ buffers/cache: 359 492 > Swap: 2015 14 2001 > > # ./usemem 1024 > 0: Mallocing 32 megabytes > 1: Mallocing 32 megabytes > 2: Mallocing 32 megabytes > 3: Mallocing 32 megabytes > 4: Mallocing 32 megabytes > 5: Mallocing 32 megabytes > 6: Mallocing 32 megabytes > 7: Mallocing 32 megabytes > 8: Mallocing 32 megabytes > 9: Mallocing 32 megabytes > 10: Mallocing 32 megabytes > 11: Mallocing 32 megabytes > 12: Mallocing 32 megabytes > 13: Mallocing 32 megabytes > 14: Mallocing 32 megabytes > 15: Mallocing 32 megabytes > Connection to 192.168.122.193 closed. > > usemem invoked oom-killer: gfp_mask=0x280da, order=0, oom_adj=0 > usemem cpuset=/ mems_allowed=0 > Pid: 1829, comm: usemem Not tainted 2.6.35-rc5+ #5 > Call Trace: > [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 > [<ffffffff81108520>] dump_header+0x70/0x190 > [<ffffffff811086c1>] oom_kill_process+0x81/0x180 > [<ffffffff81108c08>] __out_of_memory+0x58/0xd0 > [<ffffffff81108ddc>] ? out_of_memory+0x15c/0x1f0 > [<ffffffff81108d8f>] out_of_memory+0x10f/0x1f0 > [<ffffffff8110cc7f>] __alloc_pages_nodemask+0x7af/0x7c0 > [<ffffffff81140a69>] alloc_page_vma+0x89/0x140 > [<ffffffff81125f76>] handle_mm_fault+0x6d6/0x990 > [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 > [<ffffffff81121afd>] ? follow_page+0x19d/0x350 > [<ffffffff8112639c>] __get_user_pages+0x16c/0x480 > [<ffffffff810127c9>] ? sched_clock+0x9/0x10 > [<ffffffff811276ef>] __mlock_vma_pages_range+0xef/0x1f0 > [<ffffffff81127f01>] mlock_vma_pages_range+0x91/0xa0 > [<ffffffff8112ad57>] mmap_region+0x307/0x5b0 > [<ffffffff8112b354>] do_mmap_pgoff+0x354/0x3a0 > [<ffffffff8112b3fc>] ? sys_mmap_pgoff+0x5c/0x200 > [<ffffffff8112b41a>] sys_mmap_pgoff+0x7a/0x200 > [<ffffffff814e02f2>] ? trace_hardirqs_on_thunk+0x3a/0x3f > [<ffffffff8100fa09>] sys_mmap+0x29/0x30 > [<ffffffff8100b032>] system_call_fastpath+0x16/0x1b > Mem-Info: > Node 0 DMA per-cpu: > CPU 0: hi: 0, btch: 1 usd: 0 > CPU 1: hi: 0, btch: 1 usd: 0 > Node 0 DMA32 per-cpu: > CPU 0: hi: 186, btch: 31 usd: 140 > CPU 1: hi: 186, btch: 31 usd: 47 > active_anon:128 inactive_anon:140 isolated_anon:0 > active_file:0 inactive_file:9 isolated_file:0 > unevictable:126855 dirty:0 writeback:125 unstable:0 > free:1996 slab_reclaimable:4445 slab_unreclaimable:23646 > mapped:923 shmem:7 pagetables:778 bounce:0 > Node 0 DMA free:4032kB min:60kB low:72kB high:88kB active_anon:0kB > inactive_anon:0kB active_file:0kB inactive_file:0kB > unevictable:11896kB isolated(anon):0kB isolated(file):0kB > present:15756kB mlocked:11896kB dirty:0kB writeback:0kB mapped:0kB > shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB > pagetables:24kB unstable:0kB bounce:0kB writeback_tmp:0kB > pages_scanned:0 all_unreclaimable? yes > lowmem_reserve[]: 0 994 994 994 > Node 0 DMA32 free:3952kB min:4000kB low:5000kB high:6000kB > active_anon:512kB inactive_anon:560kB active_file:0kB > inactive_file:36kB unevictable:495524kB isolated(anon):0kB > isolated(file):0kB present:1018060kB mlocked:495524kB dirty:0kB > writeback:500kB mapped:3692kB shmem:28kB slab_reclaimable:17780kB > slab_unreclaimable:94584kB kernel_stack:1296kB pagetables:3088kB > unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1726 > all_unreclaimable? yes > lowmem_reserve[]: 0 0 0 0 > Node 0 DMA: 0*4kB 2*8kB 1*16kB 1*32kB 2*64kB 2*128kB 2*256kB 0*512kB > 1*1024kB 1*2048kB 0*4096kB = 4032kB > Node 0 DMA32: 476*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB > 0*512kB 0*1024kB 1*2048kB 0*4096kB = 3952kB > 1146 total pagecache pages > 215 pages in swap cache > Swap cache stats: add 19633, delete 19418, find 941/1333 > Free swap = 2051080kB > Total swap = 2064380kB > 262138 pages RAM > 43914 pages reserved > 4832 pages shared > 155665 pages non-shared > Out of memory: kill process 1727 (console-kit-dae) score 1027939 or a > child > Killed process 1727 (console-kit-dae) vsz:4111756kB, anon-rss:0kB, > file-rss:600kB > console-kit-dae invoked oom-killer: gfp_mask=0xd0, order=0, oom_adj=0 > console-kit-dae cpuset=/ mems_allowed=0 > Pid: 1752, comm: console-kit-dae Not tainted 2.6.35-rc5+ #5 > Call Trace: > [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 > [<ffffffff81108520>] dump_header+0x70/0x190 > [<ffffffff811086c1>] oom_kill_process+0x81/0x180 > [<ffffffff81108c08>] __out_of_memory+0x58/0xd0 > [<ffffffff81108ddc>] ? out_of_memory+0x15c/0x1f0 > [<ffffffff81108d8f>] out_of_memory+0x10f/0x1f0 > [<ffffffff8110cc7f>] __alloc_pages_nodemask+0x7af/0x7c0 > [<ffffffff8114522e>] kmem_getpages+0x6e/0x180 > [<ffffffff81147d79>] fallback_alloc+0x1c9/0x2b0 > [<ffffffff81147602>] ? cache_grow+0x4b2/0x520 > [<ffffffff81147a5b>] ____cache_alloc_node+0xab/0x200 > [<ffffffff810d55d5>] ? taskstats_exit+0x305/0x3b0 > [<ffffffff8114862b>] kmem_cache_alloc+0x1fb/0x290 > [<ffffffff810d55d5>] taskstats_exit+0x305/0x3b0 > [<ffffffff81063a4b>] do_exit+0x12b/0x890 > [<ffffffff810924fd>] ? trace_hardirqs_off+0xd/0x10 > [<ffffffff8108641f>] ? cpu_clock+0x6f/0x80 > [<ffffffff81095cbd>] ? lock_release_holdtime+0x3d/0x190 > [<ffffffff814e1010>] ? _raw_spin_unlock_irq+0x30/0x40 > [<ffffffff8106420e>] do_group_exit+0x5e/0xd0 > [<ffffffff81075b54>] get_signal_to_deliver+0x2d4/0x490 > [<ffffffff811ea6ad>] ? inode_has_perm+0x7d/0xf0 > [<ffffffff8100a2e5>] do_signal+0x75/0x7b0 > [<ffffffff81169d2d>] ? vfs_ioctl+0x3d/0xf0 > [<ffffffff8116a394>] ? do_vfs_ioctl+0x84/0x570 > [<ffffffff8100aa85>] do_notify_resume+0x65/0x80 > [<ffffffff814e02f2>] ? trace_hardirqs_on_thunk+0x3a/0x3f > [<ffffffff8100b381>] int_signal+0x12/0x17 > Mem-Info: > Node 0 DMA per-cpu: > CPU 0: hi: 0, btch: 1 usd: 0 > CPU 1: hi: 0, btch: 1 usd: 0 > Node 0 DMA32 per-cpu: > CPU 0: hi: 186, btch: 31 usd: 151 > CPU 1: hi: 186, btch: 31 usd: 61 > active_anon:128 inactive_anon:165 isolated_anon:0 > active_file:0 inactive_file:9 isolated_file:0 > unevictable:126855 dirty:0 writeback:25 unstable:0 > free:1965 slab_reclaimable:4445 slab_unreclaimable:23646 > mapped:923 shmem:7 pagetables:778 bounce:0 > Node 0 DMA free:4032kB min:60kB low:72kB high:88kB active_anon:0kB > inactive_anon:0kB active_file:0kB inactive_file:0kB > unevictable:11896kB isolated(anon):0kB isolated(file):0kB > present:15756kB mlocked:11896kB dirty:0kB writeback:0kB mapped:0kB > shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB > pagetables:24kB unstable:0kB bounce:0kB writeback_tmp:0kB > pages_scanned:0 all_unreclaimable? yes > lowmem_reserve[]: 0 994 994 994 > Node 0 DMA32 free:3828kB min:4000kB low:5000kB high:6000kB > active_anon:512kB inactive_anon:660kB active_file:0kB > inactive_file:36kB unevictable:495524kB isolated(anon):0kB > isolated(file):0kB present:1018060kB mlocked:495524kB dirty:0kB > writeback:100kB mapped:3692kB shmem:28kB slab_reclaimable:17780kB > slab_unreclaimable:94584kB kernel_stack:1296kB pagetables:3088kB > unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1726 > all_unreclaimable? yes > lowmem_reserve[]: 0 0 0 0 > Node 0 DMA: 0*4kB 2*8kB 1*16kB 1*32kB 2*64kB 2*128kB 2*256kB 0*512kB > 1*1024kB 1*2048kB 0*4096kB = 4032kB > Node 0 DMA32: 445*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB > 0*512kB 0*1024kB 1*2048kB 0*4096kB = 3828kB > 1146 total pagecache pages > 230 pages in swap cache > Swap cache stats: add 19649, delete 19419, find 942/1336 > Free swap = 2051084kB > Total swap = 2064380kB > 262138 pages RAM > 43914 pages reserved > 4818 pages shared > 155685 pages non-shared > Out of memory: kill process 1806 (sshd) score 9474 or a child > Killed process 1810 (bash) vsz:108384kB, anon-rss:0kB, file-rss:656kB > console-kit-dae invoked oom-killer: gfp_mask=0xd0, order=0, oom_adj=0 > console-kit-dae cpuset=/ mems_allowed=0 > Pid: 1752, comm: console-kit-dae Not tainted 2.6.35-rc5+ #5 > Call Trace: > [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 > [<ffffffff81108520>] dump_header+0x70/0x190 > [<ffffffff811086c1>] oom_kill_process+0x81/0x180 > [<ffffffff81108c08>] __out_of_memory+0x58/0xd0 > [<ffffffff81108ddc>] ? out_of_memory+0x15c/0x1f0 > [<ffffffff81108d8f>] out_of_memory+0x10f/0x1f0 > [<ffffffff8110cc7f>] __alloc_pages_nodemask+0x7af/0x7c0 > [<ffffffff8114522e>] kmem_getpages+0x6e/0x180 > [<ffffffff81147d79>] fallback_alloc+0x1c9/0x2b0 > [<ffffffff81147602>] ? cache_grow+0x4b2/0x520 > [<ffffffff81147a5b>] ____cache_alloc_node+0xab/0x200 > [<ffffffff810d55d5>] ? taskstats_exit+0x305/0x3b0 > [<ffffffff8114862b>] kmem_cache_alloc+0x1fb/0x290 > [<ffffffff810d55d5>] taskstats_exit+0x305/0x3b0 > [<ffffffff81063a4b>] do_exit+0x12b/0x890 > [<ffffffff810924fd>] ? trace_hardirqs_off+0xd/0x10 > [<ffffffff8108641f>] ? cpu_clock+0x6f/0x80 > [<ffffffff81095cbd>] ? lock_release_holdtime+0x3d/0x190 > [<ffffffff814e1010>] ? _raw_spin_unlock_irq+0x30/0x40 > [<ffffffff8106420e>] do_group_exit+0x5e/0xd0 > [<ffffffff81075b54>] get_signal_to_deliver+0x2d4/0x490 > [<ffffffff811ea6ad>] ? inode_has_perm+0x7d/0xf0 > [<ffffffff8100a2e5>] do_signal+0x75/0x7b0 > [<ffffffff81169d2d>] ? vfs_ioctl+0x3d/0xf0 > [<ffffffff8116a394>] ? do_vfs_ioctl+0x84/0x570 > [<ffffffff8100aa85>] do_notify_resume+0x65/0x80 > [<ffffffff814e02f2>] ? trace_hardirqs_on_thunk+0x3a/0x3f > [<ffffffff8100b381>] int_signal+0x12/0x17 > Mem-Info: > Node 0 DMA per-cpu: > CPU 0: hi: 0, btch: 1 usd: 0 > CPU 1: hi: 0, btch: 1 usd: 0 > Node 0 DMA32 per-cpu: > CPU 0: hi: 186, btch: 31 usd: 119 > CPU 1: hi: 186, btch: 31 usd: 73 > active_anon:50 inactive_anon:175 isolated_anon:0 > active_file:0 inactive_file:9 isolated_file:0 > unevictable:126855 dirty:0 writeback:25 unstable:0 > free:1996 slab_reclaimable:4445 slab_unreclaimable:23663 > mapped:923 shmem:7 pagetables:778 bounce:0 > Node 0 DMA free:4032kB min:60kB low:72kB high:88kB active_anon:0kB > inactive_anon:0kB active_file:0kB inactive_file:0kB > unevictable:11896kB isolated(anon):0kB isolated(file):0kB > present:15756kB mlocked:11896kB dirty:0kB writeback:0kB mapped:0kB > shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB > pagetables:24kB unstable:0kB bounce:0kB writeback_tmp:0kB > pages_scanned:0 all_unreclaimable? yes > lowmem_reserve[]: 0 994 994 994 > Node 0 DMA32 free:3952kB min:4000kB low:5000kB high:6000kB > active_anon:200kB inactive_anon:700kB active_file:0kB > inactive_file:36kB unevictable:495524kB isolated(anon):0kB > isolated(file):0kB present:1018060kB mlocked:495524kB dirty:0kB > writeback:100kB mapped:3692kB shmem:28kB slab_reclaimable:17780kB > slab_unreclaimable:94652kB kernel_stack:1296kB pagetables:3088kB > unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1536 > all_unreclaimable? yes > lowmem_reserve[]: 0 0 0 0 > Node 0 DMA: 0*4kB 2*8kB 1*16kB 1*32kB 2*64kB 2*128kB 2*256kB 0*512kB > 1*1024kB 1*2048kB 0*4096kB = 4032kB > Node 0 DMA32: 470*4kB 3*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB > 0*512kB 0*1024kB 1*2048kB 0*4096kB = 3952kB > 1146 total pagecache pages > 221 pages in swap cache > Swap cache stats: add 19848, delete 19627, find 970/1386 > Free swap = 2051428kB > Total swap = 2064380kB > 262138 pages RAM > 43914 pages reserved > 4669 pages shared > 155659 pages non-shared > Out of memory: kill process 1829 (usemem) score 8253 or a child > Killed process 1829 (usemem) vsz:528224kB, anon-rss:502468kB, > file-rss:376kB > > # cat usemem.c > # cat usemem.c > #include <stdio.h> > #include <stdlib.h> > #include <string.h> > #include <sys/mman.h> > #define CHUNKS 32 > > int > main(int argc, char *argv[]) > { > mlockall(MCL_FUTURE); > > unsigned long mb; > char *buf[CHUNKS]; > int i; > > if (argc < 2) { > fprintf(stderr, "usage: usemem megabytes\n"); > exit(1); > } > mb = strtoul(argv[1], NULL, 0); > > for (i = 0; i < CHUNKS; i++) { > fprintf(stderr, "%d: Mallocing %lu megabytes\n", i, mb/CHUNKS); > buf[i] = (char *)malloc(mb/CHUNKS * 1024L * 1024L); > if (!buf[i]) { > fprintf(stderr, "malloc failure\n"); > exit(1); > } > } > > for (i = 0; i < CHUNKS; i++) { > fprintf(stderr, "%d: Zeroing %lu megabytes at %p\n", > i, mb/CHUNKS, buf[i]); > memset(buf[i], 0, mb/CHUNKS * 1024L * 1024L); > } > > > exit(0); > } > If this ever be relevant, this was tested inside the kvm guest. The host was a RHEL6 with THP enabled. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: CAI Qian on 23 Jul 2010 14:10
Ignore me. The test case should not be using mlockall()! ----- "CAI Qian" <caiqian(a)redhat.com> wrote: > ----- caiqian(a)redhat.com wrote: > > > ----- "Nitin Gupta" <ngupta(a)vflare.org> wrote: > > > > > Frequently accessed filesystem data is stored in memory to reduce > > > access to > > > (much) slower backing disks. Under memory pressure, these pages > are > > > freed and > > > when needed again, they have to be read from disks again. When > > > combined working > > > set of all running application exceeds amount of physical RAM, we > > get > > > extereme > > > slowdown as reading a page from disk can take time in order of > > > milliseconds. > > > > > > Memory compression increases effective memory size and allows > more > > > pages to > > > stay in RAM. Since de/compressing memory pages is several orders > of > > > magnitude > > > faster than disk I/O, this can provide signifant performance > gains > > for > > > many > > > workloads. Also, with multi-cores becoming common, benefits of > > reduced > > > disk I/O > > > should easily outweigh the problem of increased CPU usage. > > > > > > It is implemented as a "backend" for cleancache_ops [1] which > > > provides > > > callbacks for events such as when a page is to be removed from > the > > > page cache > > > and when it is required again. We use them to implement a 'second > > > chance' cache > > > for these evicted page cache pages by compressing and storing > them > > in > > > memory > > > itself. > > > > > > We only keep pages that compress to PAGE_SIZE/2 or less. > Compressed > > > chunks are > > > stored using xvmalloc memory allocator which is already being > used > > by > > > zram > > > driver for the same purpose. Zero-filled pages are checked and no > > > memory is > > > allocated for them. > > > > > > A separate "pool" is created for each mount instance for a > > > cleancache-aware > > > filesystem. Each incoming page is identified with <pool_id, > > inode_no, > > > index> > > > where inode_no identifies file within the filesystem > corresponding > > to > > > pool_id > > > and index is offset of the page within this inode. Within a pool, > > > inodes are > > > maintained in an rb-tree and each of its nodes points to a > separate > > > radix-tree > > > which maintains list of pages within that inode. > > > > > > While compression reduces disk I/O, it also reduces the space > > > available for > > > normal (uncompressed) page cache. This can result in more > frequent > > > page cache > > > reclaim and thus higher CPU overhead. Thus, it's important to > > maintain > > > good hit > > > rate for compressed cache or increased CPU overhead can nullify > any > > > other > > > benefits. This requires adaptive (compressed) cache resizing and > > page > > > replacement policies that can maintain optimal cache size and > > quickly > > > reclaim > > > unused compressed chunks. This work is yet to be done. However, > in > > the > > > current > > > state, it allows manually resizing cache size using (per-pool) > > sysfs > > > node > > > 'memlimit' which in turn frees any excess pages *sigh* randomly. > > > > > > Finally, it uses percpu stats and compression buffers to allow > > better > > > performance on multi-cores. Still, there are known bottlenecks > like > > a > > > single > > > xvmalloc mempool per zcache pool and few others. I will work on > > this > > > when I > > > start with profiling. > > > > > > * Performance numbers: > > > - Tested using iozone filesystem benchmark > > > - 4 CPUs, 1G RAM > > > - Read performance gain: ~2.5X > > > - Random read performance gain: ~3X > > > - In general, performance gains for every kind of I/O > > > > > > Test details with graphs can be found here: > > > http://code.google.com/p/compcache/wiki/zcacheIOzone > > > > > > If I can get some help with testing, it would be intersting to > find > > > its > > > effect in more real-life workloads. In particular, I'm intersted > in > > > finding > > > out its effect in KVM virtualization case where it can > potentially > > > allow > > > running more number of VMs per-host for a given amount of RAM. > With > > > zcache > > > enabled, VMs can be assigned much smaller amount of memory since > > host > > > can now > > > hold bulk of page-cache pages, allowing VMs to maintain similar > > level > > > of > > > performance while a greater number of them can be hosted. > > > > > > * How to test: > > > All patches are against 2.6.35-rc5: > > > > > > - First, apply all prerequisite patches here: > > > > http://compcache.googlecode.com/hg/sub-projects/zcache_base_patches > > > > > > - Then apply this patch series; also uploaded here: > > > http://compcache.googlecode.com/hg/sub-projects/zcache_patches > > > > > > > > > Nitin Gupta (8): > > > Allow sharing xvmalloc for zram and zcache > > > Basic zcache functionality > > > Create sysfs nodes and export basic statistics > > > Shrink zcache based on memlimit > > > Eliminate zero-filled pages > > > Compress pages using LZO > > > Use xvmalloc to store compressed chunks > > > Document sysfs entries > > > > > > Documentation/ABI/testing/sysfs-kernel-mm-zcache | 53 + > > > drivers/staging/Makefile | 2 + > > > drivers/staging/zram/Kconfig | 22 + > > > drivers/staging/zram/Makefile | 5 +- > > > drivers/staging/zram/xvmalloc.c | 8 + > > > drivers/staging/zram/zcache_drv.c | 1312 > > > ++++++++++++++++++++++ > > > drivers/staging/zram/zcache_drv.h | 90 ++ > > > 7 files changed, 1491 insertions(+), 1 deletions(-) > > > create mode 100644 > > Documentation/ABI/testing/sysfs-kernel-mm-zcache > > > create mode 100644 drivers/staging/zram/zcache_drv.c > > > create mode 100644 drivers/staging/zram/zcache_drv.h > > By tested those patches on the top of the linus tree at this commit > > d0c6f6258478e1dba532bf7c28e2cd6e1047d3a4, the OOM was trigger even > > though there looked like still lots of swap. > > > > # free -m > > total used free shared buffers > > cached > > Mem: 852 379 473 0 3 > > > 15 > > -/+ buffers/cache: 359 492 > > Swap: 2015 14 2001 > > > > # ./usemem 1024 > > 0: Mallocing 32 megabytes > > 1: Mallocing 32 megabytes > > 2: Mallocing 32 megabytes > > 3: Mallocing 32 megabytes > > 4: Mallocing 32 megabytes > > 5: Mallocing 32 megabytes > > 6: Mallocing 32 megabytes > > 7: Mallocing 32 megabytes > > 8: Mallocing 32 megabytes > > 9: Mallocing 32 megabytes > > 10: Mallocing 32 megabytes > > 11: Mallocing 32 megabytes > > 12: Mallocing 32 megabytes > > 13: Mallocing 32 megabytes > > 14: Mallocing 32 megabytes > > 15: Mallocing 32 megabytes > > Connection to 192.168.122.193 closed. > > > > usemem invoked oom-killer: gfp_mask=0x280da, order=0, oom_adj=0 > > usemem cpuset=/ mems_allowed=0 > > Pid: 1829, comm: usemem Not tainted 2.6.35-rc5+ #5 > > Call Trace: > > [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 > > [<ffffffff81108520>] dump_header+0x70/0x190 > > [<ffffffff811086c1>] oom_kill_process+0x81/0x180 > > [<ffffffff81108c08>] __out_of_memory+0x58/0xd0 > > [<ffffffff81108ddc>] ? out_of_memory+0x15c/0x1f0 > > [<ffffffff81108d8f>] out_of_memory+0x10f/0x1f0 > > [<ffffffff8110cc7f>] __alloc_pages_nodemask+0x7af/0x7c0 > > [<ffffffff81140a69>] alloc_page_vma+0x89/0x140 > > [<ffffffff81125f76>] handle_mm_fault+0x6d6/0x990 > > [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 > > [<ffffffff81121afd>] ? follow_page+0x19d/0x350 > > [<ffffffff8112639c>] __get_user_pages+0x16c/0x480 > > [<ffffffff810127c9>] ? sched_clock+0x9/0x10 > > [<ffffffff811276ef>] __mlock_vma_pages_range+0xef/0x1f0 > > [<ffffffff81127f01>] mlock_vma_pages_range+0x91/0xa0 > > [<ffffffff8112ad57>] mmap_region+0x307/0x5b0 > > [<ffffffff8112b354>] do_mmap_pgoff+0x354/0x3a0 > > [<ffffffff8112b3fc>] ? sys_mmap_pgoff+0x5c/0x200 > > [<ffffffff8112b41a>] sys_mmap_pgoff+0x7a/0x200 > > [<ffffffff814e02f2>] ? trace_hardirqs_on_thunk+0x3a/0x3f > > [<ffffffff8100fa09>] sys_mmap+0x29/0x30 > > [<ffffffff8100b032>] system_call_fastpath+0x16/0x1b > > Mem-Info: > > Node 0 DMA per-cpu: > > CPU 0: hi: 0, btch: 1 usd: 0 > > CPU 1: hi: 0, btch: 1 usd: 0 > > Node 0 DMA32 per-cpu: > > CPU 0: hi: 186, btch: 31 usd: 140 > > CPU 1: hi: 186, btch: 31 usd: 47 > > active_anon:128 inactive_anon:140 isolated_anon:0 > > active_file:0 inactive_file:9 isolated_file:0 > > unevictable:126855 dirty:0 writeback:125 unstable:0 > > free:1996 slab_reclaimable:4445 slab_unreclaimable:23646 > > mapped:923 shmem:7 pagetables:778 bounce:0 > > Node 0 DMA free:4032kB min:60kB low:72kB high:88kB active_anon:0kB > > inactive_anon:0kB active_file:0kB inactive_file:0kB > > unevictable:11896kB isolated(anon):0kB isolated(file):0kB > > present:15756kB mlocked:11896kB dirty:0kB writeback:0kB mapped:0kB > > shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB > kernel_stack:0kB > > pagetables:24kB unstable:0kB bounce:0kB writeback_tmp:0kB > > pages_scanned:0 all_unreclaimable? yes > > lowmem_reserve[]: 0 994 994 994 > > Node 0 DMA32 free:3952kB min:4000kB low:5000kB high:6000kB > > active_anon:512kB inactive_anon:560kB active_file:0kB > > inactive_file:36kB unevictable:495524kB isolated(anon):0kB > > isolated(file):0kB present:1018060kB mlocked:495524kB dirty:0kB > > writeback:500kB mapped:3692kB shmem:28kB slab_reclaimable:17780kB > > slab_unreclaimable:94584kB kernel_stack:1296kB pagetables:3088kB > > unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1726 > > all_unreclaimable? yes > > lowmem_reserve[]: 0 0 0 0 > > Node 0 DMA: 0*4kB 2*8kB 1*16kB 1*32kB 2*64kB 2*128kB 2*256kB > 0*512kB > > 1*1024kB 1*2048kB 0*4096kB = 4032kB > > Node 0 DMA32: 476*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB > > 0*512kB 0*1024kB 1*2048kB 0*4096kB = 3952kB > > 1146 total pagecache pages > > 215 pages in swap cache > > Swap cache stats: add 19633, delete 19418, find 941/1333 > > Free swap = 2051080kB > > Total swap = 2064380kB > > 262138 pages RAM > > 43914 pages reserved > > 4832 pages shared > > 155665 pages non-shared > > Out of memory: kill process 1727 (console-kit-dae) score 1027939 or > a > > child > > Killed process 1727 (console-kit-dae) vsz:4111756kB, anon-rss:0kB, > > file-rss:600kB > > console-kit-dae invoked oom-killer: gfp_mask=0xd0, order=0, > oom_adj=0 > > console-kit-dae cpuset=/ mems_allowed=0 > > Pid: 1752, comm: console-kit-dae Not tainted 2.6.35-rc5+ #5 > > Call Trace: > > [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 > > [<ffffffff81108520>] dump_header+0x70/0x190 > > [<ffffffff811086c1>] oom_kill_process+0x81/0x180 > > [<ffffffff81108c08>] __out_of_memory+0x58/0xd0 > > [<ffffffff81108ddc>] ? out_of_memory+0x15c/0x1f0 > > [<ffffffff81108d8f>] out_of_memory+0x10f/0x1f0 > > [<ffffffff8110cc7f>] __alloc_pages_nodemask+0x7af/0x7c0 > > [<ffffffff8114522e>] kmem_getpages+0x6e/0x180 > > [<ffffffff81147d79>] fallback_alloc+0x1c9/0x2b0 > > [<ffffffff81147602>] ? cache_grow+0x4b2/0x520 > > [<ffffffff81147a5b>] ____cache_alloc_node+0xab/0x200 > > [<ffffffff810d55d5>] ? taskstats_exit+0x305/0x3b0 > > [<ffffffff8114862b>] kmem_cache_alloc+0x1fb/0x290 > > [<ffffffff810d55d5>] taskstats_exit+0x305/0x3b0 > > [<ffffffff81063a4b>] do_exit+0x12b/0x890 > > [<ffffffff810924fd>] ? trace_hardirqs_off+0xd/0x10 > > [<ffffffff8108641f>] ? cpu_clock+0x6f/0x80 > > [<ffffffff81095cbd>] ? lock_release_holdtime+0x3d/0x190 > > [<ffffffff814e1010>] ? _raw_spin_unlock_irq+0x30/0x40 > > [<ffffffff8106420e>] do_group_exit+0x5e/0xd0 > > [<ffffffff81075b54>] get_signal_to_deliver+0x2d4/0x490 > > [<ffffffff811ea6ad>] ? inode_has_perm+0x7d/0xf0 > > [<ffffffff8100a2e5>] do_signal+0x75/0x7b0 > > [<ffffffff81169d2d>] ? vfs_ioctl+0x3d/0xf0 > > [<ffffffff8116a394>] ? do_vfs_ioctl+0x84/0x570 > > [<ffffffff8100aa85>] do_notify_resume+0x65/0x80 > > [<ffffffff814e02f2>] ? trace_hardirqs_on_thunk+0x3a/0x3f > > [<ffffffff8100b381>] int_signal+0x12/0x17 > > Mem-Info: > > Node 0 DMA per-cpu: > > CPU 0: hi: 0, btch: 1 usd: 0 > > CPU 1: hi: 0, btch: 1 usd: 0 > > Node 0 DMA32 per-cpu: > > CPU 0: hi: 186, btch: 31 usd: 151 > > CPU 1: hi: 186, btch: 31 usd: 61 > > active_anon:128 inactive_anon:165 isolated_anon:0 > > active_file:0 inactive_file:9 isolated_file:0 > > unevictable:126855 dirty:0 writeback:25 unstable:0 > > free:1965 slab_reclaimable:4445 slab_unreclaimable:23646 > > mapped:923 shmem:7 pagetables:778 bounce:0 > > Node 0 DMA free:4032kB min:60kB low:72kB high:88kB active_anon:0kB > > inactive_anon:0kB active_file:0kB inactive_file:0kB > > unevictable:11896kB isolated(anon):0kB isolated(file):0kB > > present:15756kB mlocked:11896kB dirty:0kB writeback:0kB mapped:0kB > > shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB > kernel_stack:0kB > > pagetables:24kB unstable:0kB bounce:0kB writeback_tmp:0kB > > pages_scanned:0 all_unreclaimable? yes > > lowmem_reserve[]: 0 994 994 994 > > Node 0 DMA32 free:3828kB min:4000kB low:5000kB high:6000kB > > active_anon:512kB inactive_anon:660kB active_file:0kB > > inactive_file:36kB unevictable:495524kB isolated(anon):0kB > > isolated(file):0kB present:1018060kB mlocked:495524kB dirty:0kB > > writeback:100kB mapped:3692kB shmem:28kB slab_reclaimable:17780kB > > slab_unreclaimable:94584kB kernel_stack:1296kB pagetables:3088kB > > unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1726 > > all_unreclaimable? yes > > lowmem_reserve[]: 0 0 0 0 > > Node 0 DMA: 0*4kB 2*8kB 1*16kB 1*32kB 2*64kB 2*128kB 2*256kB > 0*512kB > > 1*1024kB 1*2048kB 0*4096kB = 4032kB > > Node 0 DMA32: 445*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB > > 0*512kB 0*1024kB 1*2048kB 0*4096kB = 3828kB > > 1146 total pagecache pages > > 230 pages in swap cache > > Swap cache stats: add 19649, delete 19419, find 942/1336 > > Free swap = 2051084kB > > Total swap = 2064380kB > > 262138 pages RAM > > 43914 pages reserved > > 4818 pages shared > > 155685 pages non-shared > > Out of memory: kill process 1806 (sshd) score 9474 or a child > > Killed process 1810 (bash) vsz:108384kB, anon-rss:0kB, > file-rss:656kB > > console-kit-dae invoked oom-killer: gfp_mask=0xd0, order=0, > oom_adj=0 > > console-kit-dae cpuset=/ mems_allowed=0 > > Pid: 1752, comm: console-kit-dae Not tainted 2.6.35-rc5+ #5 > > Call Trace: > > [<ffffffff814e10cb>] ? _raw_spin_unlock+0x2b/0x40 > > [<ffffffff81108520>] dump_header+0x70/0x190 > > [<ffffffff811086c1>] oom_kill_process+0x81/0x180 > > [<ffffffff81108c08>] __out_of_memory+0x58/0xd0 > > [<ffffffff81108ddc>] ? out_of_memory+0x15c/0x1f0 > > [<ffffffff81108d8f>] out_of_memory+0x10f/0x1f0 > > [<ffffffff8110cc7f>] __alloc_pages_nodemask+0x7af/0x7c0 > > [<ffffffff8114522e>] kmem_getpages+0x6e/0x180 > > [<ffffffff81147d79>] fallback_alloc+0x1c9/0x2b0 > > [<ffffffff81147602>] ? cache_grow+0x4b2/0x520 > > [<ffffffff81147a5b>] ____cache_alloc_node+0xab/0x200 > > [<ffffffff810d55d5>] ? taskstats_exit+0x305/0x3b0 > > [<ffffffff8114862b>] kmem_cache_alloc+0x1fb/0x290 > > [<ffffffff810d55d5>] taskstats_exit+0x305/0x3b0 > > [<ffffffff81063a4b>] do_exit+0x12b/0x890 > > [<ffffffff810924fd>] ? trace_hardirqs_off+0xd/0x10 > > [<ffffffff8108641f>] ? cpu_clock+0x6f/0x80 > > [<ffffffff81095cbd>] ? lock_release_holdtime+0x3d/0x190 > > [<ffffffff814e1010>] ? _raw_spin_unlock_irq+0x30/0x40 > > [<ffffffff8106420e>] do_group_exit+0x5e/0xd0 > > [<ffffffff81075b54>] get_signal_to_deliver+0x2d4/0x490 > > [<ffffffff811ea6ad>] ? inode_has_perm+0x7d/0xf0 > > [<ffffffff8100a2e5>] do_signal+0x75/0x7b0 > > [<ffffffff81169d2d>] ? vfs_ioctl+0x3d/0xf0 > > [<ffffffff8116a394>] ? do_vfs_ioctl+0x84/0x570 > > [<ffffffff8100aa85>] do_notify_resume+0x65/0x80 > > [<ffffffff814e02f2>] ? trace_hardirqs_on_thunk+0x3a/0x3f > > [<ffffffff8100b381>] int_signal+0x12/0x17 > > Mem-Info: > > Node 0 DMA per-cpu: > > CPU 0: hi: 0, btch: 1 usd: 0 > > CPU 1: hi: 0, btch: 1 usd: 0 > > Node 0 DMA32 per-cpu: > > CPU 0: hi: 186, btch: 31 usd: 119 > > CPU 1: hi: 186, btch: 31 usd: 73 > > active_anon:50 inactive_anon:175 isolated_anon:0 > > active_file:0 inactive_file:9 isolated_file:0 > > unevictable:126855 dirty:0 writeback:25 unstable:0 > > free:1996 slab_reclaimable:4445 slab_unreclaimable:23663 > > mapped:923 shmem:7 pagetables:778 bounce:0 > > Node 0 DMA free:4032kB min:60kB low:72kB high:88kB active_anon:0kB > > inactive_anon:0kB active_file:0kB inactive_file:0kB > > unevictable:11896kB isolated(anon):0kB isolated(file):0kB > > present:15756kB mlocked:11896kB dirty:0kB writeback:0kB mapped:0kB > > shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB > kernel_stack:0kB > > pagetables:24kB unstable:0kB bounce:0kB writeback_tmp:0kB > > pages_scanned:0 all_unreclaimable? yes > > lowmem_reserve[]: 0 994 994 994 > > Node 0 DMA32 free:3952kB min:4000kB low:5000kB high:6000kB > > active_anon:200kB inactive_anon:700kB active_file:0kB > > inactive_file:36kB unevictable:495524kB isolated(anon):0kB > > isolated(file):0kB present:1018060kB mlocked:495524kB dirty:0kB > > writeback:100kB mapped:3692kB shmem:28kB slab_reclaimable:17780kB > > slab_unreclaimable:94652kB kernel_stack:1296kB pagetables:3088kB > > unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1536 > > all_unreclaimable? yes > > lowmem_reserve[]: 0 0 0 0 > > Node 0 DMA: 0*4kB 2*8kB 1*16kB 1*32kB 2*64kB 2*128kB 2*256kB > 0*512kB > > 1*1024kB 1*2048kB 0*4096kB = 4032kB > > Node 0 DMA32: 470*4kB 3*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB > > 0*512kB 0*1024kB 1*2048kB 0*4096kB = 3952kB > > 1146 total pagecache pages > > 221 pages in swap cache > > Swap cache stats: add 19848, delete 19627, find 970/1386 > > Free swap = 2051428kB > > Total swap = 2064380kB > > 262138 pages RAM > > 43914 pages reserved > > 4669 pages shared > > 155659 pages non-shared > > Out of memory: kill process 1829 (usemem) score 8253 or a child > > Killed process 1829 (usemem) vsz:528224kB, anon-rss:502468kB, > > file-rss:376kB > > > > # cat usemem.c > > # cat usemem.c > > #include <stdio.h> > > #include <stdlib.h> > > #include <string.h> > > #include <sys/mman.h> > > #define CHUNKS 32 > > > > int > > main(int argc, char *argv[]) > > { > > mlockall(MCL_FUTURE); > > > > unsigned long mb; > > char *buf[CHUNKS]; > > int i; > > > > if (argc < 2) { > > fprintf(stderr, "usage: usemem megabytes\n"); > > exit(1); > > } > > mb = strtoul(argv[1], NULL, 0); > > > > for (i = 0; i < CHUNKS; i++) { > > fprintf(stderr, "%d: Mallocing %lu megabytes\n", i, mb/CHUNKS); > > buf[i] = (char *)malloc(mb/CHUNKS * 1024L * 1024L); > > if (!buf[i]) { > > fprintf(stderr, "malloc failure\n"); > > exit(1); > > } > > } > > > > for (i = 0; i < CHUNKS; i++) { > > fprintf(stderr, "%d: Zeroing %lu megabytes at %p\n", > > i, mb/CHUNKS, buf[i]); > > memset(buf[i], 0, mb/CHUNKS * 1024L * 1024L); > > } > > > > > > exit(0); > > } > > > If this ever be relevant, this was tested inside the kvm guest. The > host was a RHEL6 with THP enabled. > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo(a)kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont(a)kvack.org"> email(a)kvack.org </a> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |