Defrag in shrinkers
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From: Andi Kleen on 14 May 2010 16:40 Christoph Lameter <cl(a)linux.com> writes: > Would it also be possible to add some defragmentation logic when you > revise the shrinkers? Here is a prototype patch that would allow you to > determine the other objects sitting in the same page as a given object. > > With that I hope that you have enough information to determine if its > worth to evict the other objects as well to reclaim the slab page. I like the idea, it would be useful for the hwpoison code too, when it tries to clean a page. -Andi -- ak(a)linux.intel.com -- Speaking for myself only. -- 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: Ed Tomlinson on 15 May 2010 13:10 On Friday 14 May 2010 16:36:03 Andi Kleen wrote: > Christoph Lameter <cl(a)linux.com> writes: > > > Would it also be possible to add some defragmentation logic when you > > revise the shrinkers? Here is a prototype patch that would allow you to > > determine the other objects sitting in the same page as a given object. > > > > With that I hope that you have enough information to determine if its > > worth to evict the other objects as well to reclaim the slab page. > > I like the idea, it would be useful for the hwpoison code too, > when it tries to clean a page. If this is done generally we probably want to retune the 'pressure' put on the slab. The whole reason for the callbacks was to keep the 'pressure on the slab proportional to the memory pressure (scan rate). Ed Tomlinson -- 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: Dave Chinner on 16 May 2010 20:30
On Sat, May 15, 2010 at 01:08:17PM -0400, Ed Tomlinson wrote: > On Friday 14 May 2010 16:36:03 Andi Kleen wrote: > > Christoph Lameter <cl(a)linux.com> writes: > > > > > Would it also be possible to add some defragmentation logic when you > > > revise the shrinkers? Here is a prototype patch that would allow you to > > > determine the other objects sitting in the same page as a given object. > > > > > > With that I hope that you have enough information to determine if its > > > worth to evict the other objects as well to reclaim the slab page. > > > > I like the idea, it would be useful for the hwpoison code too, > > when it tries to clean a page. > > If this is done generally we probably want to retune the 'pressure' put on the slab. The > whole reason for the callbacks was to keep the 'pressure on the slab proportional to the > memory pressure (scan rate). I don't see that defrag based reclaim changes the concept of pressure at all. As long as reclaim follows the nr_to_scan guideline, then it doesn't matter if we do reclaim from the LRU or reclaim from a list provided by the slab cache.... FWIW, one thing that would be necessary, I think, is to avoid defrag until a certain level of fragmentation has occurred - we should do LRU-based reclaim as much as possible, and only trigger defrag-style reclaim once we hit a trigger (e.g. once the slab is 25% partial pages). Cheers, Dave. -- Dave Chinner david(a)fromorbit.com -- 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/ |