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Thu, 22 Oct 2020 14:51:46 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id A1B4EAC6C; Thu, 22 Oct 2020 14:51:45 +0000 (UTC) Subject: Re: [PATCH] mm,thp,shmem: limit shmem THP alloc gfp_mask To: Rik van Riel , Hugh Dickins Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Mel Gorman , Andrea Arcangeli , Matthew Wilcox , Michal Hocko References: <20201021234846.5cc97e62@imladris.surriel.com> From: Vlastimil Babka Message-ID: <06c1e573-cddd-c17c-9f18-3af2d9d09f80@suse.cz> Date: Thu, 22 Oct 2020 16:51:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.2 MIME-Version: 1.0 In-Reply-To: <20201021234846.5cc97e62@imladris.surriel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 10/22/20 5:48 AM, Rik van Riel wrote: > The allocation flags of anonymous transparent huge pages can be controlled > through the files in /sys/kernel/mm/transparent_hugepage/defrag, which can > help the system from getting bogged down in the page reclaim and compaction > code when many THPs are getting allocated simultaneously. > > However, the gfp_mask for shmem THP allocations were not limited by those > configuration settings, and some workloads ended up with all CPUs stuck > on the LRU lock in the page reclaim code, trying to allocate dozens of > THPs simultaneously. > > This patch applies the same configurated limitation of THPs to shmem > hugepage allocations, to prevent that from happening. > > This way a THP defrag setting of "never" or "defer+madvise" will result > in quick allocation failures without direct reclaim when no 2MB free > pages are available. > > Signed-off-by: Rik van Riel FTR, a patch to the same effect was sent by Xu Yu: https://lore.kernel.org/r/11e1ead211eb7d141efa0eb75a46ee2096ee63f8.1603267572.git.xuyu@linux.alibaba.com > --- > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > index c603237e006c..0a5b164a26d9 100644 > --- a/include/linux/gfp.h > +++ b/include/linux/gfp.h > @@ -614,6 +614,8 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask); > extern void pm_restrict_gfp_mask(void); > extern void pm_restore_gfp_mask(void); > > +extern gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma); > + > #ifdef CONFIG_PM_SLEEP > extern bool pm_suspended_storage(void); > #else > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 9474dbc150ed..9b08ce5cc387 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -649,7 +649,7 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf, > * available > * never: never stall for any thp allocation > */ > -static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma) > +gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma) > { > const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE); > > diff --git a/mm/shmem.c b/mm/shmem.c > index 537c137698f8..d1290eb508e5 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1545,8 +1545,11 @@ static struct page *shmem_alloc_hugepage(gfp_t gfp, > return NULL; > > shmem_pseudo_vma_init(&pvma, info, hindex); > - page = alloc_pages_vma(gfp | __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN, > - HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(), true); > + /* Limit the gfp mask according to THP configuration. */ > + gfp |= __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN; > + gfp &= alloc_hugepage_direct_gfpmask(&pvma); > + page = alloc_pages_vma(gfp, HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(), > + true); > shmem_pseudo_vma_destroy(&pvma); > if (page) > prep_transhuge_page(page); >