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Message-ID: <20090115113037.GH30358@balbir.in.ibm.com>
Date: Thu, 15 Jan 2009 17:00:37 +0530
From: Balbir Singh <balbir@...ux.vnet.ibm.com>
To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
lizf@...fujitsu.com, menage@...gle.com,
Hugh Dickins <hugh@...itas.com>
Subject: Re: [PATCH] mark_page_accessed() in do_swap_page() move latter
than memcg charge
* KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> [2009-01-15 20:08:36]:
>
> sorry for late responce.
>
> > > In this case we've hit a case where the page is valid and the pc is
> > > not. This does fix the problem, but won't this impact us getting
> > > correct reclaim stats and thus indirectly impact the working of
> > > pressure?
> > >
> > - If retruns NULL, only global LRU's status is updated.
> >
> > Because this page is not belongs to any memcg, we cannot update
> > any counters. But yes, your point is a concern.
> >
> > Maybe moving acitvate_page() to
> > ==
> > do_swap_page()
> > {
> >
> > - activate_page()
> > mem_cgroup_try_charge()..
> > ....
> > mem_cgroup_commit_charge()....
> > ....
> > + activate_page()
> > }
> > ==
> > is necessary. How do you think, kosaki ?
>
>
> OK. it makes sense. and my test found no bug.
>
> ==
>
> mark_page_accessed() update reclaim_stat statics.
> but currently, memcg charge is called after mark_page_accessed().
>
> then, mark_page_accessed() don't update memcg statics correctly.
>
> fixing here.
>
Changelog needs to be a bit more elaborate, may be talk about invalid
pointer we hit if mark_page_accessed is not moved, etc.
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Cc: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
> Cc: Balbir Singh <balbir@...ux.vnet.ibm.com>
>
> ---
> mm/memory.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> Index: b/mm/memory.c
> ===================================================================
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2426,8 +2426,6 @@ static int do_swap_page(struct mm_struct
> count_vm_event(PGMAJFAULT);
> }
>
> - mark_page_accessed(page);
> -
> lock_page(page);
> delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
>
> @@ -2480,6 +2478,8 @@ static int do_swap_page(struct mm_struct
> try_to_free_swap(page);
> unlock_page(page);
>
> + mark_page_accessed(page);
> +
> if (write_access) {
> ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
> if (ret & VM_FAULT_ERROR)
>
>
>
Looks good to me otherwise
Reviewed-by: Balbir Singh <balbir@...ux.vnet.ibm.com>
--
Balbir
--
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