From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f52.google.com (mail-oi0-f52.google.com [209.85.218.52]) by kanga.kvack.org (Postfix) with ESMTP id 61439828DF for ; Fri, 15 Jan 2016 07:54:09 -0500 (EST) Received: by mail-oi0-f52.google.com with SMTP id w75so103350954oie.0 for ; Fri, 15 Jan 2016 04:54:09 -0800 (PST) Received: from mail-oi0-x242.google.com (mail-oi0-x242.google.com. [2607:f8b0:4003:c06::242]) by mx.google.com with ESMTPS id m133si13298163oia.143.2016.01.15.04.54.08 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Jan 2016 04:54:08 -0800 (PST) Received: by mail-oi0-x242.google.com with SMTP id j3so8378545oig.0 for ; Fri, 15 Jan 2016 04:54:08 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20160113081611.GA29313@hori1.linux.bs1.fc.nec.co.jp> References: <1452138758-30031-1-git-send-email-liangchen.linux@gmail.com> <20160113081611.GA29313@hori1.linux.bs1.fc.nec.co.jp> Date: Fri, 15 Jan 2016 20:54:08 +0800 Message-ID: Subject: Re: [PATCH V2] mm: mempolicy: skip non-migratable VMAs when setting MPOL_MF_LAZY From: Liang Chen Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: "riel@redhat.com" , "mgorman@suse.de" , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Gavin Guo Hi Naoya, Yeah. Thanks for the reminding=EF=BC=81 vma_policy_mof doesn't need to be checked because with MPOL_MF_LAZY do_mbind always sets the MPOL_F_MOF flag. VM_HUGETLB and VM_MIXEDMAP vma should be excluded to avoid compound pages being marked for migration and unexpected COWs when handling hugetlb fault. I will send a patch to add these check soon. Thanks, Liang On Wed, Jan 13, 2016 at 4:16 PM, Naoya Horiguchi wrote: > Hello Liang, > > On Thu, Jan 07, 2016 at 11:52:38AM +0800, Liang Chen wrote: >> MPOL_MF_LAZY is not visible from userspace since 'commit a720094ded8c >> ("mm: mempolicy: Hide MPOL_NOOP and MPOL_MF_LAZY from userspace for now"= )' >> , but it should still skip non-migratable VMAs such as VM_IO, VM_PFNMAP, >> and VM_HUGETLB VMAs, and avoid useless overhead of minor faults. >> >> Signed-off-by: Liang Chen >> Signed-off-by: Gavin Guo >> --- >> Changes since v2: >> - Add more description into the changelog >> >> We have been evaluating the enablement of MPOL_MF_LAZY again, and found >> this issue. And we decided to push this patch upstream no matter if we >> finally determine to propose re-enablement of MPOL_MF_LAZY or not. Since >> it can be a potential problem even if MPOL_MF_LAZY is not enabled this >> time. >> --- >> mm/mempolicy.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/mm/mempolicy.c b/mm/mempolicy.c >> index 87a1779..436ff411 100644 >> --- a/mm/mempolicy.c >> +++ b/mm/mempolicy.c >> @@ -610,7 +610,8 @@ static int queue_pages_test_walk(unsigned long start= , unsigned long end, >> >> if (flags & MPOL_MF_LAZY) { >> /* Similar to task_numa_work, skip inaccessible VMAs */ >> - if (vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)) >> + if (vma_migratable(vma) && >> + vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)) >> change_prot_numa(vma, start, endvma); >> return 1; >> } > > task_numa_work() does more vma checks before entering change_prot_numa() = like > vma_policy_mof(), is_vm_hugetlb_page(), and (vma->vm_flags & VM_MIXEDMAP)= . > So is it better to use the same check set to limit the target vmas to aut= o-numa > enabled ones? > > Thanks, > Naoya Horiguchi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org