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Thu, 22 Oct 2020 16:00:33 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R141e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=alimailimapcm10staff010182156082;MF=xuyu@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0UCrLpdS_1603382424; Received: from xuyu-mbp15.local(mailfrom:xuyu@linux.alibaba.com fp:SMTPD_---0UCrLpdS_1603382424) by smtp.aliyun-inc.com(127.0.0.1); Fri, 23 Oct 2020 00:00:25 +0800 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 References: <20201021234846.5cc97e62@imladris.surriel.com> From: Yu Xu Message-ID: Date: Fri, 23 Oct 2020 00:00:22 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 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 11:48 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 > --- > > 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); It is fine to reuse `alloc_hugepage_direct_gfpmask`, but `pvma.vm_flags & VM_HUGEPAGE` is always false here, thus, `vma_madvised` in `alloc_hugepage_direct_gfpmask` will always be false. That is why I chose to do the gfp_mask fixup in `shmem_getpage_gfp`, using `sgp_huge` to indicate `vma_madvised`, although with some silly mistakes pointed out by you, in another mail thread. It will be better if vma_madvised is well handled in your solution. > + 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); > -- Thanks, Yu