From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f71.google.com (mail-pl0-f71.google.com [209.85.160.71]) by kanga.kvack.org (Postfix) with ESMTP id 2C47E6B000C for ; Fri, 22 Jun 2018 12:44:48 -0400 (EDT) Received: by mail-pl0-f71.google.com with SMTP id y7-v6so3937415plt.17 for ; Fri, 22 Jun 2018 09:44:48 -0700 (PDT) Received: from out4438.biz.mail.alibaba.com (out4438.biz.mail.alibaba.com. [47.88.44.38]) by mx.google.com with ESMTPS id 97-v6si8311301pld.345.2018.06.22.09.44.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 Jun 2018 09:44:46 -0700 (PDT) Subject: Re: [v2 PATCH 1/2] mm: thp: register mm for khugepaged when merging vma for shmem References: <1529622949-75504-1-git-send-email-yang.shi@linux.alibaba.com> <20180622075958.mzagr2ayufiuokea@black.fi.intel.com> <20180622161912.sq32cnhfxo5ctgdp@black.fi.intel.com> From: Yang Shi Message-ID: <6e59a56d-7bb3-76d3-201a-8a4ad4638602@linux.alibaba.com> Date: Fri, 22 Jun 2018 09:44:27 -0700 MIME-Version: 1.0 In-Reply-To: <20180622161912.sq32cnhfxo5ctgdp@black.fi.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: hughd@google.com, vbabka@suse.cz, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On 6/22/18 9:19 AM, Kirill A. Shutemov wrote: > On Fri, Jun 22, 2018 at 04:04:12PM +0000, yang.shi@linux.alibaba.com wrote: >> >> On 6/22/18 12:59 AM, Kirill A. Shutemov wrote: >>> On Thu, Jun 21, 2018 at 11:15:48PM +0000, yang.shi@linux.alibaba.com wrote: >>>> When merging anonymous page vma, if the size of vma can fit in at least >>>> one hugepage, the mm will be registered for khugepaged for collapsing >>>> THP in the future. >>>> >>>> But, it skips shmem vma. Doing so for shmem too, but not file-private >>>> mapping, when merging vma in order to increase the odd to collapse >>>> hugepage by khugepaged. >>>> >>>> Signed-off-by: Yang Shi >>>> Cc: Hugh Dickins >>>> Cc: Kirill A. Shutemov >>>> Cc: Vlastimil Babka >>>> --- >>>> v1 --> 2: >>>> * Exclude file-private mapping per Kirill's comment >>>> >>>> mm/khugepaged.c | 8 ++++++-- >>>> 1 file changed, 6 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>>> index d7b2a4b..9b0ec30 100644 >>>> --- a/mm/khugepaged.c >>>> +++ b/mm/khugepaged.c >>>> @@ -440,8 +440,12 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma, >>>> * page fault if needed. >>>> */ >>>> return 0; >>>> - if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED)) >>>> - /* khugepaged not yet working on file or special mappings */ >>>> + if ((vma->vm_ops && (!shmem_file(vma->vm_file) || vma->anon_vma)) || >>>> + (vm_flags & VM_NO_KHUGEPAGED)) >>>> + /* >>>> + * khugepaged not yet working on non-shmem file or special >>>> + * mappings. And, file-private shmem THP is not supported. >>>> + */ >>>> return 0; >>> My point was that vma->anon_vma check above this one should not prevent >>> collapse for shmem. >>> >>> Looking into this more, I think we should just replace all these checks >>> with hugepage_vma_check() call. >> I got a little bit confused here. I thought the condition to *not* collapse >> file-private shmem mapping should be: >> >> shmem_file(vma->vm_file) && vma->anon_vma >> >> Is this right? > No, if shmem_file(vma->vm_file) is true, vma->anon_vma doesn't matter. > We don't care about anon_vma in such VMA as we don't touch file-private > pages. Thanks, I misunderstood that. hugepage_vma_check() sounds reasonable. Will fix in v3 soon. Yang >