Messages in this thread | | | Subject | Re: [PATCH] prevent to reclaim anon page of lumpy reclaim for no swap space | From | Lee Schermerhorn <> | Date | Thu, 25 Jun 2009 10:54:25 -0400 |
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On Thu, 2009-06-25 at 23:44 +0900, Minchan Kim wrote: > On Thu, Jun 25, 2009 at 11:14 PM, KOSAKI > Motohiro<kosaki.motohiro@jp.fujitsu.com> wrote: > >> This patch prevent to reclaim anon page in case of no swap space. > >> VM already prevent to reclaim anon page in various place. > >> But it doesnt't prevent it for lumpy reclaim. > >> > >> It shuffles lru list unnecessary so that it is pointless. > > > > NAK. > > > > 1. if system have no swap, add_to_swap() never get swap entry. > > eary check don't improve performance so much. > > Hmm. I mean no swap space but not no swap device. > add_to_swap ? You mean Rik pointed me out ? > If system have swap device, Rik's pointing is right. > I will update his suggestion. > > > 2. __isolate_lru_page() is not only called lumpy reclaim case, but > > also be called > > normal reclaim. > > You mean about performance degradation ? > I think most case have enough swap space and then one condition > variable(nr_swap_page) check is trivial. I think. > We can also use [un]likely but I am not sure it help us. > > > > 3. if system have no swap, anon pages shuffuling doesn't cause any matter. > > Again, I mean no swap space but no swap device system. > And I have a plan to remove anon_vma in no swap device system. > > As you point me out, it's pointless in no swap device system. > I don't like unnecessary structure memory footprint and locking overhead. > I think no swap device system is problem in server environment as well > as embedded. but I am not sure when I will do. :) >
How will we walk the reverse map for try_to_unmap() for page migration or try_to_munlock() w/o anon_vma? Perhaps one can remove anon_vma when there is no swap device and migration and the unevictable lru are not configured--e.g., for embedded systems.
Lee
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