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[209.85.220.65]) by mx.google.com with SMTPS id m37sor30484630pla.6.2019.07.17.12.44.33 for (Google Transport Security); Wed, 17 Jul 2019 12:44:33 -0700 (PDT) Received-SPF: pass (google.com: domain of hughd@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=V+41nzxS; spf=pass (google.com: domain of hughd@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=hughd@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=gvjPZWoufoHncj5iyWeqiWRKnFrwf8zGjNBYtpZ6tKQ=; b=V+41nzxSMtHHtuKjjlYe2GfJUL8OkwTW54lqpP4dzM4zgY3shyyLaX0K65MjCbgkMA JbEoFVMktVLB3yjSnRHiCY/QGDeT/Ry1EtepMiiQZBtORT4LcsanPu+wmDHPU5A8ImJZ ldVpzOO2iZ7YzyDbWT2fLzrjfofjjisJtzT8oJ+LheNWez/iuEh8rIrXccIbc6wOmENU bymQc2QANDdpuvEugqEqUY33+9C5zNaq8aNQvWYnJfl2VIYp+NDrL1dmaf/yoMoe+wia PQa0y1K4sc3F7Xf58nEjx6tNNBQQWv75mlgYI1ha4k6Jhx5wCMoMPtZyRCR9AsEli8l9 8+aw== X-Google-Smtp-Source: APXvYqxyIhVLV3+xZdZyruXl0Q+nykHdkO769WGjExr3291Arvp8ld8l1OClYHmZUBHqkGiwRJjaKw== X-Received: by 2002:a17:902:9041:: with SMTP id w1mr46275249plz.132.1563392672552; Wed, 17 Jul 2019 12:44:32 -0700 (PDT) Received: from [100.112.64.100] ([104.133.8.100]) by smtp.gmail.com with ESMTPSA id 14sm24016805pfy.40.2019.07.17.12.44.31 (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 17 Jul 2019 12:44:31 -0700 (PDT) Date: Wed, 17 Jul 2019 12:44:30 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Yang Shi cc: hughd@google.com, kirill.shutemov@linux.intel.com, mhocko@suse.com, vbabka@suse.cz, rientjes@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [v3 PATCH 2/2] mm: thp: fix false negative of shmem vma's THP eligibility In-Reply-To: <1560401041-32207-3-git-send-email-yang.shi@linux.alibaba.com> Message-ID: References: <1560401041-32207-1-git-send-email-yang.shi@linux.alibaba.com> <1560401041-32207-3-git-send-email-yang.shi@linux.alibaba.com> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII 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 Thu, 13 Jun 2019, Yang Shi wrote: > The commit 7635d9cbe832 ("mm, thp, proc: report THP eligibility for each > vma") introduced THPeligible bit for processes' smaps. But, when checking > the eligibility for shmem vma, __transparent_hugepage_enabled() is > called to override the result from shmem_huge_enabled(). It may result > in the anonymous vma's THP flag override shmem's. For example, running a > simple test which create THP for shmem, but with anonymous THP disabled, > when reading the process's smaps, it may show: > > 7fc92ec00000-7fc92f000000 rw-s 00000000 00:14 27764 /dev/shm/test > Size: 4096 kB > ... > [snip] > ... > ShmemPmdMapped: 4096 kB > ... > [snip] > ... > THPeligible: 0 > > And, /proc/meminfo does show THP allocated and PMD mapped too: > > ShmemHugePages: 4096 kB > ShmemPmdMapped: 4096 kB > > This doesn't make too much sense. The shmem objects should be treated > separately from anonymous THP. Calling shmem_huge_enabled() with checking > MMF_DISABLE_THP sounds good enough. And, we could skip stack and > dax vma check since we already checked if the vma is shmem already. > > Also check if vma is suitable for THP by calling > transhuge_vma_suitable(). > > And minor fix to smaps output format and documentation. > > Fixes: 7635d9cbe832 ("mm, thp, proc: report THP eligibility for each vma") > Cc: Hugh Dickins Thanks, Acked-by: Hugh Dickins > Cc: Kirill A. Shutemov > Cc: Michal Hocko > Cc: Vlastimil Babka > Cc: David Rientjes > Signed-off-by: Yang Shi > --- > Documentation/filesystems/proc.txt | 4 ++-- > fs/proc/task_mmu.c | 3 ++- > mm/huge_memory.c | 9 +++++++-- > mm/shmem.c | 3 +++ > 4 files changed, 14 insertions(+), 5 deletions(-) > > diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt > index 66cad5c..b0ded06 100644 > --- a/Documentation/filesystems/proc.txt > +++ b/Documentation/filesystems/proc.txt > @@ -477,8 +477,8 @@ replaced by copy-on-write) part of the underlying shmem object out on swap. > "SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this > does not take into account swapped out page of underlying shmem objects. > "Locked" indicates whether the mapping is locked in memory or not. > -"THPeligible" indicates whether the mapping is eligible for THP pages - 1 if > -true, 0 otherwise. > +"THPeligible" indicates whether the mapping is eligible for allocating THP > +pages - 1 if true, 0 otherwise. It just shows the current status. > > "VmFlags" field deserves a separate description. This member represents the kernel > flags associated with the particular virtual memory area in two letter encoded > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 01d4eb0..6a13882 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -796,7 +796,8 @@ static int show_smap(struct seq_file *m, void *v) > > __show_smap(m, &mss); > > - seq_printf(m, "THPeligible: %d\n", transparent_hugepage_enabled(vma)); > + seq_printf(m, "THPeligible: %d\n", > + transparent_hugepage_enabled(vma)); > > if (arch_pkeys_enabled()) > seq_printf(m, "ProtectionKey: %8u\n", vma_pkey(vma)); > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 4bc2552..36f0225 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -65,10 +65,15 @@ > > bool transparent_hugepage_enabled(struct vm_area_struct *vma) > { > + /* The addr is used to check if the vma size fits */ > + unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE; > + > + if (!transhuge_vma_suitable(vma, addr)) > + return false; > if (vma_is_anonymous(vma)) > return __transparent_hugepage_enabled(vma); > - if (vma_is_shmem(vma) && shmem_huge_enabled(vma)) > - return __transparent_hugepage_enabled(vma); > + if (vma_is_shmem(vma)) > + return shmem_huge_enabled(vma); > > return false; > } > diff --git a/mm/shmem.c b/mm/shmem.c > index 1bb3b8d..a807712 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -3872,6 +3872,9 @@ bool shmem_huge_enabled(struct vm_area_struct *vma) > loff_t i_size; > pgoff_t off; > > + if ((vma->vm_flags & VM_NOHUGEPAGE) || > + test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) > + return false; > if (shmem_huge == SHMEM_HUGE_FORCE) > return true; > if (shmem_huge == SHMEM_HUGE_DENY) > -- > 1.8.3.1