linux-kernel - Re: [PATCH] mm: vmscan: check mem cgroup over reclaimed

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120123104731.GA1707@cmpxchg.org>
Date:	Mon, 23 Jan 2012 11:47:40 +0100
From:	Johannes Weiner <hannes@...xchg.org>
To:	Hillf Danton <dhillf@...il.com>
Cc:	linux-mm@...ck.org, Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Ying Han <yinghan@...gle.com>, Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: vmscan: check mem cgroup over reclaimed

On Mon, Jan 23, 2012 at 09:55:07AM +0800, Hillf Danton wrote:
> To avoid reduction in performance of reclaimee, checking overreclaim is added
> after shrinking lru list, when pages are reclaimed from mem cgroup.
> 
> If over reclaim occurs, shrinking remaining lru lists is skipped, and no more
> reclaim for reclaim/compaction.
> 
> Signed-off-by: Hillf Danton <dhillf@...il.com>
> ---
> 
> --- a/mm/vmscan.c	Mon Jan 23 00:23:10 2012
> +++ b/mm/vmscan.c	Mon Jan 23 09:57:20 2012
> @@ -2086,6 +2086,7 @@ static void shrink_mem_cgroup_zone(int p
>  	unsigned long nr_reclaimed, nr_scanned;
>  	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
>  	struct blk_plug plug;
> +	bool memcg_over_reclaimed = false;
> 
>  restart:
>  	nr_reclaimed = 0;
> @@ -2103,6 +2104,11 @@ restart:
> 
>  				nr_reclaimed += shrink_list(lru, nr_to_scan,
>  							    mz, sc, priority);
> +
> +				memcg_over_reclaimed = !scanning_global_lru(mz)
> +					&& (nr_reclaimed >= nr_to_reclaim);
> +				if (memcg_over_reclaimed)
> +					goto out;

Since this merge window, scanning_global_lru() is always false when
the memory controller is enabled, i.e. most common configurations and
distribution kernels.

This will with quite likely have bad effects on zone balancing,
pressure balancing between anon/file lru etc, while you haven't shown
that any workloads actually benefit from this.

Submitting patches like this without mentioning a problematic scenario
and numbers that demonstrate that the patch improve it is not helpful.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/