From: Nitin Gupta on
The zram module creates RAM based block devices named /dev/zram<id>
(<id> = 0, 1, ...). Pages written to these disks are compressed and stored
in memory itself.

One of the major changes done is the replacement of ioctls with sysfs
interface. One of the advantages of this approach is we no longer depend on the
userspace tool (rzscontrol) which was used to set various parameters and check
statistics. Maintaining updated version of rzscontrol as changes were done to
ioctls, statistics exported etc. was a major pain.

Another significant change is the introduction of percpu stats and compression
buffers. Earlier, we had per-device buffers protected by a mutex. This was a
major bottleneck on multi-core systems. With these changes, benchmarks with
fio[1] showed a speedup of about 20% for write performance on dual-core
system (see patch 4/10 description for details).

For easier testing, a single patch against 2.6.35-git8 has been uploaded at:

[1] fio I/O benchmarking tool:

Nitin Gupta (10):
Replace ioctls with sysfs interface
Remove need for explicit device initialization
Use percpu stats
Use percpu buffers
Reduce per table entry overhead by 4 bytes
Block discard support
Increase compressed page size threshold
Some cleanups
Update zram documentation
Document sysfs entries

Documentation/ABI/testing/sysfs-block-zram | 99 ++++
drivers/staging/zram/Kconfig | 12 -
drivers/staging/zram/Makefile | 2 +-
drivers/staging/zram/xvmalloc.c | 22 +-
drivers/staging/zram/zram.txt | 58 ++-
drivers/staging/zram/zram_drv.c | 670 ++++++++++++++--------------
drivers/staging/zram/zram_drv.h | 138 ++----
drivers/staging/zram/zram_ioctl.h | 41 --
drivers/staging/zram/zram_sysfs.c | 253 +++++++++++
9 files changed, 760 insertions(+), 535 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-block-zram
delete mode 100644 drivers/staging/zram/zram_ioctl.h
create mode 100644 drivers/staging/zram/zram_sysfs.c


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