linux-kernel - Re: [PATCH -V3] /proc/PID/smaps: Add PMD migration entry parsing

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Date:   Mon, 6 Apr 2020 10:19:02 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     "Huang, Ying" <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Zi Yan <ziy@...dia.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Michal Hocko <mhocko@...e.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Jérôme Glisse <jglisse@...hat.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>
Subject: Re: [PATCH -V3] /proc/PID/smaps: Add PMD migration entry parsing

On 4/3/20 2:30 PM, Huang, Ying wrote:
> From: Huang Ying <ying.huang@...el.com>
> 
> Now, when read /proc/PID/smaps, the PMD migration entry in page table is simply
> ignored.  To improve the accuracy of /proc/PID/smaps, its parsing and processing
> is added.
> 
> To test the patch, we run pmbench to eat 400 MB memory in background, then run
> /usr/bin/migratepages and `cat /proc/PID/smaps` every second.  The issue as
> follows can be reproduced within 60 seconds.
> 
> Before the patch, for the fully populated 400 MB anonymous VMA, some THP pages
> under migration may be lost as below.
> 
> 7f3f6a7e5000-7f3f837e5000 rw-p 00000000 00:00 0
> Size:             409600 kB
> KernelPageSize:        4 kB
> MMUPageSize:           4 kB
> Rss:              407552 kB
> Pss:              407552 kB
> Shared_Clean:          0 kB
> Shared_Dirty:          0 kB
> Private_Clean:         0 kB
> Private_Dirty:    407552 kB
> Referenced:       301056 kB
> Anonymous:        407552 kB
> LazyFree:              0 kB
> AnonHugePages:    405504 kB
> ShmemPmdMapped:        0 kB
> FilePmdMapped:        0 kB
> Shared_Hugetlb:        0 kB
> Private_Hugetlb:       0 kB
> Swap:                  0 kB
> SwapPss:               0 kB
> Locked:                0 kB
> THPeligible:		1
> VmFlags: rd wr mr mw me ac
> 
> After the patch, it will be always,
> 
> 7f3f6a7e5000-7f3f837e5000 rw-p 00000000 00:00 0
> Size:             409600 kB
> KernelPageSize:        4 kB
> MMUPageSize:           4 kB
> Rss:              409600 kB
> Pss:              409600 kB
> Shared_Clean:          0 kB
> Shared_Dirty:          0 kB
> Private_Clean:         0 kB
> Private_Dirty:    409600 kB
> Referenced:       294912 kB
> Anonymous:        409600 kB
> LazyFree:              0 kB
> AnonHugePages:    407552 kB
> ShmemPmdMapped:        0 kB
> FilePmdMapped:        0 kB
> Shared_Hugetlb:        0 kB
> Private_Hugetlb:       0 kB
> Swap:                  0 kB
> SwapPss:               0 kB
> Locked:                0 kB
> THPeligible:		1
> VmFlags: rd wr mr mw me ac
> 
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
> Reviewed-by: Zi Yan <ziy@...dia.com>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Alexey Dobriyan <adobriyan@...il.com>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> Cc: "Jérôme Glisse" <jglisse@...hat.com>
> Cc: Yang Shi <yang.shi@...ux.alibaba.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>
Thanks!