linux-kernel - Re: [PATCH 5/3] mm, vmscan: make zone_reclaimable

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Message-ID: <20160129151755.GE32174@dhcp22.suse.cz>
Date:	Fri, 29 Jan 2016 16:17:55 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	hannes@...xchg.org, mgorman@...e.de, rientjes@...gle.com,
	hillf.zj@...baba-inc.com, kamezawa.hiroyu@...fujitsu.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/3] mm, vmscan: make zone_reclaimable_pages more precise

On Fri 29-01-16 19:35:18, Tetsuo Handa wrote:
> Michal Hocko wrote:
> > From: Michal Hocko <mhocko@...e.com>
> > 
> > zone_reclaimable_pages is used in should_reclaim_retry which uses it to
> > calculate the target for the watermark check. This means that precise
> > numbers are important for the correct decision. zone_reclaimable_pages
> > uses zone_page_state which can contain stale data with per-cpu diffs
> > not synced yet (the last vmstat_update might have run 1s in the past).
> > 
> > Use zone_page_state_snapshot in zone_reclaimable_pages instead. None
> > of the current callers is in a hot path where getting the precise value
> > (which involves per-cpu iteration) would cause an unreasonable overhead.
> > 
> > Suggested-by: David Rientjes <rientjes@...gle.com>
> > Signed-off-by: Michal Hocko <mhocko@...e.com>
> > ---
> >  mm/vmscan.c | 14 +++++++-------
> >  1 file changed, 7 insertions(+), 7 deletions(-)
> > 
> 
> I didn't know http://lkml.kernel.org/r/20151021130323.GC8805@dhcp22.suse.cz
> was forgotten. Anyway,

OK, that explains why this sounded so familiar. Sorry I comepletely
forgot about it.

> Acked-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

Can I change it to your Signed-off-by?

-- 
Michal Hocko
SUSE Labs