[lkml]   [2011]   [Nov]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [patch 8/8] mm: memcg: modify PageCgroupCache non-atomically
On Thu, Nov 24, 2011 at 09:13:28AM +0900, KAMEZAWA Hiroyuki wrote:
> On Wed, 23 Nov 2011 16:42:31 +0100
> Johannes Weiner <> wrote:
> > From: Johannes Weiner <>
> >
> > This bit is protected by lock_page_cgroup(), there is no need for
> > locked operations when setting and clearing it.
> >
> > Signed-off-by: Johannes Weiner <>
> Hm. non-atomic ops for pc->flags seems dangerous.
> How about try to remove PCG_CACHE ? Maybe we can depends on PageAnon(page).
> We see 'page' on memcg->lru now.
> I'm sorry I forgot why we needed PCG_CACHE flag..

The problem is that we charge/uncharged pages that are not fully
rmapped and so PageAnon() is not reliable. I forgot if there are more
places, but the commit_charge in migration was a prominent one.

I have a patch set that reworks migration so to only commit pages that
are fully rmapped but it clashed with the THP patches and I didn't see
too much value to fix it up. But I should probably revive it, because
it makes some things simpler.

As I replied to Hugh, it might even work for PCG_CACHE, but it's
definitely dangerous and not worth the complex dependencies it brings
on other parts of the code, so please consider 7/8 and 8/8 dropped.

 \ /
  Last update: 2011-11-24 10:15    [W:0.191 / U:1.048 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site