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From: Andrew Morton <akpm@linux-foundation.org>
To: zhong jiang <zhongjiang@huawei.com>
Cc: <osalvador@suse.de>, <khandual@linux.vnet.ibm.com>,
	<mhocko@suse.com>, <mgorman@techsingularity.net>,
	<aarcange@redhat.com>, <rcampbell@nvidia.com>,
	<linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH] mm/mempolicy: Fix an incorrect rebind node in mpol_rebind_nodemask
Date: Sat, 25 May 2019 11:28:51 -0700	[thread overview]
Message-ID: <20190525112851.ee196bcbbc33bf9e0d869236@linux-foundation.org> (raw)
In-Reply-To: <1558768043-23184-1-git-send-email-zhongjiang@huawei.com>

(Cc Vlastimil)

On Sat, 25 May 2019 15:07:23 +0800 zhong jiang <zhongjiang@huawei.com> wrote:

> We bind an different node to different vma, Unluckily,
> it will bind different vma to same node by checking the /proc/pid/numa_maps.   
> Commit 213980c0f23b ("mm, mempolicy: simplify rebinding mempolicies when updating cpusets")
> has introduced the issue.  when we change memory policy by seting cpuset.mems,
> A process will rebind the specified policy more than one times. 
> if the cpuset_mems_allowed is not equal to user specified nodes. hence the issue will trigger.
> Maybe result in the out of memory which allocating memory from same node.
> 
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -345,7 +345,7 @@ static void mpol_rebind_nodemask(struct mempolicy *pol, const nodemask_t *nodes)
>  	else {
>  		nodes_remap(tmp, pol->v.nodes,pol->w.cpuset_mems_allowed,
>  								*nodes);
> -		pol->w.cpuset_mems_allowed = tmp;
> +		pol->w.cpuset_mems_allowed = *nodes;
>  	}
>  
>  	if (nodes_empty(tmp))

hm, I'm not surprised the code broke.  What the heck is going on in
there?  It used to have a perfunctory comment, but Vlastimil deleted
it.

Could someone please propose a comment for the above code block
explaining why we're doing what we do?


  reply	other threads:[~2019-05-25 18:28 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-25  7:07 zhong jiang
2019-05-25 18:28 ` Andrew Morton [this message]
2019-05-27 12:23   ` Vlastimil Babka
2019-05-27 13:58     ` zhong jiang
2019-06-27  3:57       ` Andrew Morton
2019-06-27  7:47         ` Vlastimil Babka
2019-06-27  9:59 ` Vlastimil Babka

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