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Date: Tue, 28 Jul 2020 10:40:22 +0800 From: Muchun Song <songmuchun@...edance.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: mike.kravetz@...cle.com, Michal Hocko <mhocko@...nel.org>, David Rientjes <rientjes@...gle.com>, mgorman@...e.de, Michel Lespinasse <walken@...gle.com>, Linux Memory Management List <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Jianchao Guo <guojianchao@...edance.com> Subject: Re: [External] Re: [PATCH v3] mm/hugetlb: add mempolicy check in the reservation routine On Tue, Jul 28, 2020 at 8:19 AM Andrew Morton <akpm@...ux-foundation.org> wrote: > > On Sat, 25 Jul 2020 16:07:49 +0800 Muchun Song <songmuchun@...edance.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? > OK. I will do that, thanks. -- Yours, Muchun
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