linux-kernel - Re: [PATCH][for -mm] fix accounting in vmscan.c for memory controller

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Date:	Tue, 11 Dec 2007 10:44:36 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"yamamoto@...inux.co.jp" <yamamoto@...inux.co.jp>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"riel@...hat.com" <riel@...hat.com>
Subject: Re: [PATCH][for -mm] fix accounting in vmscan.c for memory controller

KAMEZAWA Hiroyuki wrote:
> Without this, ALLOCSTALL and PGSCAN_DIRECT increases too much unless
> there is no memory shortage.
> 
> against 2.6.24-rc4-mm1.
> 
> -Kame
> 
> ==
> Some amount of accounting is done while page reclaiming.
> 
> Now, there are 2 types of page reclaim (if memory controller is used)
>   - global: shortage of (global) pages.
>   - under cgroup: use up to limit.
> 
> I think 2 accountings, ALLOCSTALL and DIRECT should be accounted only under
> global lru scan. They are accounted against memory shortage at alloc_pages().
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
>  mm/vmscan.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6.24-rc4-mm1/mm/vmscan.c
> ===================================================================
> --- linux-2.6.24-rc4-mm1.orig/mm/vmscan.c
> +++ linux-2.6.24-rc4-mm1/mm/vmscan.c
> @@ -896,8 +896,9 @@ static unsigned long shrink_inactive_lis
>  		if (current_is_kswapd()) {
>  			__count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
>  			__count_vm_events(KSWAPD_STEAL, nr_freed);
> -		} else
> +		} else if (scan_global_lru(sc))
>  			__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
> +
>  		__count_zone_vm_events(PGSTEAL, zone, nr_freed);
> 
>  		if (nr_taken == 0)
> @@ -1333,7 +1334,8 @@ static unsigned long do_try_to_free_page
>  	unsigned long lru_pages = 0;
>  	int i;
> 
> -	count_vm_event(ALLOCSTALL);
> +	if (scan_global_lru(sc))
> +		count_vm_event(ALLOCSTALL);
>  	/*
>  	 * mem_cgroup will not do shrink_slab.
>  	 */
> 

Looks good to me.

Acked-by: Balbir Singh <balbir@...ux.vnet.ibm.com>

TODO:

1. Should we have vm_events for the memory controller as well?
   May be in the longer term

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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