From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id ED1806B0003 for ; Fri, 22 Jun 2018 12:04:29 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id a12-v6so3389176pfn.12 for ; Fri, 22 Jun 2018 09:04:29 -0700 (PDT) Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com. [115.124.30.130]) by mx.google.com with ESMTPS id r25-v6si7845523pff.24.2018.06.22.09.04.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 Jun 2018 09:04:28 -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> From: Yang Shi Message-ID: Date: Fri, 22 Jun 2018 09:04:12 -0700 MIME-Version: 1.0 In-Reply-To: <20180622075958.mzagr2ayufiuokea@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 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? If it is right, it looks hugepage_vma_check() can't do this since it just returns true if shmem_file is true and it is page aligned without checking vma->anon_vma. Thanks, Yang >