linux-kernel - Re: [PATCH 3/6] memcg: make throttle_vm

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Date:	Fri, 19 Nov 2010 12:16:52 +0100
From:	Johannes Weiner <hannes@...xchg.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Greg Thelen <gthelen@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Minchan Kim <minchan.kim@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] memcg: make throttle_vm_writeout() memcg aware

Hello,

On Tue, Nov 16, 2010 at 12:57:26PM +0900, KAMEZAWA Hiroyuki wrote:
> Hmm. I think this patch is troublesome.
> 
> This patch will make memcg's pageout routine _not_ throttoled even when the whole
> system vmscan's pageout is throttoled.
> 
> So, one idea is....
> 
> Make this change 
> ==
> +++ b/mm/vmscan.c
> @@ -1844,7 +1844,7 @@ static void shrink_zone(int priority, struct zone *zone,
>  	if (inactive_anon_is_low(zone, sc))
>  		shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
>  
> -	throttle_vm_writeout(sc->gfp_mask);
> +	throttle_vm_writeout(sc->gfp_mask, sc->mem_cgroup);
>  }
> ==
> as
> 
> ==
> 	
> if (!sc->mem_cgroup || throttle_vm_writeout(sc->gfp_mask, sc->mem_cgroup) == not throttled)
> 	throttole_vm_writeout(sc->gfp_mask, NULL);
> 
> Then, both of memcg and global dirty thresh will be checked.

Good point, both limits should apply.

I'd prefer to stuff it all into throttle_vm_writeout() and not encode
memcg-specific behaviour into the caller, though.
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