linux-kernel - Re: [patch] mm: memcontrol: default hierarchy interface for memory fix

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Message-ID: <20150120132519.GH25342@dhcp22.suse.cz>
Date:	Tue, 20 Jan 2015 14:25:19 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Vladimir Davydov <vdavydov@...allels.com>,
	Greg Thelen <gthelen@...gle.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch] mm: memcontrol: default hierarchy interface for memory
 fix - high reclaim

On Sat 17-01-15 10:21:19, Johannes Weiner wrote:
> High limit reclaim can currently overscan in proportion to how many
> charges are happening concurrently.  Tone it down such that charges
> don't target the entire high-boundary excess, but instead only the
> pages they charged themselves when excess is detected.
> 
> Reported-by: Michal Hocko <mhocko@...e.cz>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

I certainly agree with this approach.
Acked-by: Michal Hocko <mhocko@...e.cz>

Is this planned to be folded into the original patch or go on its own. I
am OK with both ways, maybe having it separate would be better from
documentation POV.

> ---
>  mm/memcontrol.c | 16 +++++-----------
>  1 file changed, 5 insertions(+), 11 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 323a01fa1833..7adccee9fecb 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2348,19 +2348,13 @@ done_restock:
>  		refill_stock(memcg, batch - nr_pages);
>  	/*
>  	 * If the hierarchy is above the normal consumption range,
> -	 * make the charging task trim the excess.
> +	 * make the charging task trim their excess contribution.
>  	 */
>  	do {
> -		unsigned long nr_pages = page_counter_read(&memcg->memory);
> -		unsigned long high = ACCESS_ONCE(memcg->high);
> -
> -		if (nr_pages > high) {
> -			mem_cgroup_events(memcg, MEMCG_HIGH, 1);
> -
> -			try_to_free_mem_cgroup_pages(memcg, nr_pages - high,
> -						     gfp_mask, true);
> -		}
> -
> +		if (page_counter_read(&memcg->memory) <= memcg->high)
> +			continue;
> +		mem_cgroup_events(memcg, MEMCG_HIGH, 1);
> +		try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask, true);
>  	} while ((memcg = parent_mem_cgroup(memcg)));
>  done:
>  	return ret;
> -- 
> 2.2.0
> 

-- 
Michal Hocko
SUSE Labs
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