Re: [RFC] [PATCH 1/7 v2] memcg: remove unnecessary check in mem_cgroup_update_page_stat()

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Thu, 19 Jan 2012 12:07:22 -0800
Ying Han <yinghan@google.com> wrote:

> On Wed, Jan 18, 2012 at 5:01 AM, Michal Hocko <mhocko@suse.cz> wrote:
> > On Wed 18-01-12 08:55:58, KAMEZAWA Hiroyuki wrote:
> >> On Tue, 17 Jan 2012 16:16:20 +0100
> >> Michal Hocko <mhocko@suse.cz> wrote:
> >>
> >> > On Fri 13-01-12 17:32:27, KAMEZAWA Hiroyuki wrote:
> >> > >
> >> > > From 788aebf15f3fa37940e0745cab72547e20683bf2 Mon Sep 17 00:00:00 2001
> >> > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> >> > > Date: Thu, 12 Jan 2012 16:08:33 +0900
> >> > > Subject: [PATCH 1/7] memcg: remove unnecessary check in mem_cgroup_update_page_stat()
> >> > >
> >> > > commit 10ea69f1182b removes move_lock_page_cgroup() in thp-split path.
> >> > > So, this PageTransHuge() check is unnecessary, too.
> >> >
> >> > I do not see commit like that in the tree. I guess you meant
> >> > memcg: make mem_cgroup_split_huge_fixup() more efficient which is not
> >> > merged yet, right?
> >> >
> >>
> >> This commit in the linux-next.
> >
> > Referring to commits from linux-next is tricky as it changes all the
> > time. I guess that the full commit subject should be sufficient.
> >
> >> > > Note:
> >> > > A - considering when mem_cgroup_update_page_stat() is called,
> >> > > A  A there will be no race between split_huge_page() and update_page_stat().
> >> > > A  A All required locks are held in higher level.
> >> >
> >> > We should never have THP page in this path in the first place. So why
> >> > not changing this to VM_BUG_ON(PageTransHuge).
> >> >
> >>
> >> Ying Han considers to support mlock stat.
> >
> > OK, got it. What about the following updated changelog instead?
> >
> > ===
> > We do not have to check PageTransHuge in mem_cgroup_update_page_stat
> > and fallback into the locked accounting because both move charge and thp
> 
> one nitpick. Should it be "move account" instead of "move charge"?
> 
Ah, yes. you'r right.
Considering Michal's comment, I'll update and post v3.

Thanks,
-Kame

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