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From: Andrew Morton <akpm@linux-foundation.org>
To: Muchun Song <songmuchun@bytedance.com>
Cc: mike.kravetz@oracle.com, mhocko@kernel.org, rientjes@google.com,
	mgorman@suse.de, walken@google.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org,
	Jianchao Guo <guojianchao@bytedance.com>
Subject: Re: [PATCH v3] mm/hugetlb: add mempolicy check in the reservation routine
Date: Mon, 27 Jul 2020 17:19:53 -0700	[thread overview]
Message-ID: <20200727171953.443afb897bb88261facf5512@linux-foundation.org> (raw)
In-Reply-To: <20200725080749.70470-1-songmuchun@bytedance.com>

On Sat, 25 Jul 2020 16:07:49 +0800 Muchun Song <songmuchun@bytedance.com> wrote:

> In the reservation routine, we only check whether the cpuset meets
> the memory allocation requirements. But we ignore the mempolicy of
> MPOL_BIND case. If someone mmap hugetlb succeeds, but the subsequent
> memory allocation may fail due to mempolicy restrictions and receives
> the SIGBUS signal. This can be reproduced by the follow steps.
> 
>  1) Compile the test case.
>     cd tools/testing/selftests/vm/
>     gcc map_hugetlb.c -o map_hugetlb
> 
>  2) Pre-allocate huge pages. Suppose there are 2 numa nodes in the
>     system. Each node will pre-allocate one huge page.
>     echo 2 > /proc/sys/vm/nr_hugepages
> 
>  3) Run test case(mmap 4MB). We receive the SIGBUS signal.
>     numactl --membind=0 ./map_hugetlb 4
> 
> With this patch applied, the mmap will fail in the step 3) and throw
> "mmap: Cannot allocate memory".

This doesn't compile with CONFIG_NUMA=n - ther eis no implementation of
get_task_policy().

I think it needs more than a simple build fix - can we please rework
the patch so that its impact (mainly code size) on non-NUMA machines is
minimized?



  parent reply	other threads:[~2020-07-28  0:19 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-25  8:07 [PATCH v3] mm/hugetlb: add mempolicy check in the reservation routine Muchun Song
2020-07-27 23:09 ` Mike Kravetz
2020-07-28  0:19 ` Andrew Morton [this message]
2020-07-28  2:40   ` [External] " Muchun Song
2020-07-28  2:42   ` Mike Kravetz

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