linux-kernel - Re: meminfo Committed

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Date:	Wed, 15 Apr 2009 09:04:55 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Dave Hansen <dave@...ux.vnet.ibm.com>,
	linux-mm <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Eric B Munson <ebmunson@...ibm.com>,
	Mel Gorman <mel@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: meminfo Committed_AS underflows

* KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> [2009-04-15 11:04:59]:

>  	committed = atomic_long_read(&vm_committed_space);
> +	if (committed < 0)
> +		committed = 0;

Isn't this like pushing the problem under the rug?

>  	allowed = ((totalram_pages - hugetlb_total_pages())
>  		* sysctl_overcommit_ratio / 100) + total_swap_pages;
> 
> Index: b/mm/swap.c
> ===================================================================
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -519,7 +519,7 @@ EXPORT_SYMBOL(pagevec_lookup_tag);
>   * We tolerate a little inaccuracy to avoid ping-ponging the counter between
>   * CPUs
>   */
> -#define ACCT_THRESHOLD	max(16, NR_CPUS * 2)
> +#define ACCT_THRESHOLD	max_t(long, 16, num_online_cpus() * 2)
>

Hmm.. this is a one time expansion, free of CPU hotplug.

Should we use nr_cpu_ids or num_possible_cpus()?
 

-- 
	Balbir
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