linux-kernel - Re: [PATCH v5] proc/ksm: add ksm stats to /proc/pid/smaps

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Message-ID: <1f6b4edb-b906-e1ba-7c1f-c854472ad304@redhat.com>
Date:   Wed, 23 Aug 2023 20:30:56 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Stefan Roesch <shr@...kernel.io>, kernel-team@...com
Cc:     akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
        hannes@...xchg.org, riel@...riel.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v5] proc/ksm: add ksm stats to /proc/pid/smaps

On 23.08.23 19:01, Stefan Roesch wrote:
> With madvise and prctl KSM can be enabled for different VMA's. Once it
> is enabled we can query how effective KSM is overall. However we cannot
> easily query if an individual VMA benefits from KSM.
> 
> This commit adds a KSM section to the /prod/<pid>/smaps file. It reports
> how many of the pages are KSM pages. Note that KSM-placed zeropages are
> not included, only actual KSM pages.
> 
> Here is a typical output:
> 
> 7f420a000000-7f421a000000 rw-p 00000000 00:00 0
> Size:             262144 kB
> KernelPageSize:        4 kB
> MMUPageSize:           4 kB
> Rss:               51212 kB
> Pss:                8276 kB
> Shared_Clean:        172 kB
> Shared_Dirty:      42996 kB
> Private_Clean:       196 kB
> Private_Dirty:      7848 kB
> Referenced:        15388 kB
> Anonymous:         51212 kB
> KSM:               41376 kB
> LazyFree:              0 kB
> AnonHugePages:         0 kB
> ShmemPmdMapped:        0 kB
> FilePmdMapped:         0 kB
> Shared_Hugetlb:        0 kB
> Private_Hugetlb:       0 kB
> Swap:             202016 kB
> SwapPss:            3882 kB
> Locked:                0 kB
> THPeligible:    0
> ProtectionKey:         0
> ksm_state:          0
> ksm_skip_base:      0
> ksm_skip_count:     0
> VmFlags: rd wr mr mw me nr mg anon
> 
> This information also helps with the following workflow:
> - First enable KSM for all the VMA's of a process with prctl.
> - Then analyze with the above smaps report which VMA's benefit the most
> - Change the application (if possible) to add the corresponding madvise
> calls for the VMA's that benefit the most
> 
> Signed-off-by: Stefan Roesch <shr@...kernel.io>

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb