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Date: Fri, 08 Jun 2012 00:50:19 -0400 From: KOSAKI Motohiro <kosaki.motohiro@...il.com> To: John Stultz <john.stultz@...aro.org> CC: Dave Hansen <dave@...ux.vnet.ibm.com>, Dmitry Adamushko <dmitry.adamushko@...il.com>, KOSAKI Motohiro <kosaki.motohiro@...il.com>, LKML <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>, Android Kernel Team <kernel-team@...roid.com>, Robert Love <rlove@...gle.com>, Mel Gorman <mel@....ul.ie>, Hugh Dickins <hughd@...gle.com>, Rik van Riel <riel@...hat.com>, Dave Chinner <david@...morbit.com>, Neil Brown <neilb@...e.de>, Andrea Righi <andrea@...terlinux.com>, "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>, Taras Glek <tgek@...illa.com>, Mike Hommey <mh@...ndium.org>, Jan Kara <jack@...e.cz> Subject: Re: [PATCH 3/3] [RFC] tmpfs: Add FALLOC_FL_MARK_VOLATILE/UNMARK_VOLATILE handlers (6/7/12 11:03 PM), John Stultz wrote: > On 06/07/2012 04:41 PM, Dave Hansen wrote: >> On 06/07/2012 03:55 AM, Dmitry Adamushko wrote: >>> but maybe we should also purge them before we swap out some non-tmpfs >>> pages or drop some file-backed pages? >> >> Sure... I guess we could kick that from either direct reclaim or from >> kswapd. But, then we're basically back to the places where >> shrink_slab() is called. >> >> I think that means that we think it's preferable to integrate this more >> directly in the VM instead of sticking it off in the corner of tmpfs >> only, or pretending it's a slab. >> >> Dunno... The slab shrinker one isn't looking _so_ bad at the moment. > > Dave also pointed out to me on irc that on a system without swap, >shmem_writepage doesn't even get called, which kills the utility of >triggering volatile purging from writepage. Ah, right you are. swap-less system never try to reclaim anon pages. So, volatile pages is no longer swap backed. swap backed lru is no longer suitable place. > So I'm falling back to using a shrinker for now, but I think Dmitry's >point is an interesting one, and am interested in finding a better >place to trigger purging volatile ranges from the mm code. If anyone has any >suggestions, let me know, otherwise I'll go back to trying to better grok the mm code. I hate vm feature to abuse shrink_slab(). because of, it was not designed generic callback. it was designed for shrinking filesystem metadata. Therefore, vm keeping a balance between page scanning and slab scanning. then, a lot of shrink_slab misuse may lead to break balancing logic. i.e. drop icache/dcache too many and makes perfomance impact. As far as a code impact is small, I'm prefer to connect w/ vm reclaim code directly. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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