linux-kernel - Re: [PATCH v2] ksm: allow dedup all tasks memory

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Date:   Sun, 11 Nov 2018 19:58:38 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Timofey Titovets <timofey.titovets@...esis.ru>
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, Timofey Titovets <nefelim4ag@...il.com>
Subject: Re: [PATCH v2] ksm: allow dedup all tasks memory

On Mon, Nov 12, 2018 at 12:26:10AM +0300, Timofey Titovets wrote:
> ksm by default working only on memory that added by
> madvice().
> 
> And only way get that work on other applications:
>  - Use LD_PRELOAD and libraries
>  - Patch kernel
> 
> Lets use kernel task list in ksm_scan_thread and add logic to allow ksm
> import VMA from tasks.
> That behaviour controlled by new attribute: mode
> I try mimic hugepages attribute, so mode have two states:
>  - normal       - old default behaviour
>  - always [new] - allow ksm to get tasks vma and try working on that.
> 
> To reduce CPU load & tasklist locking time,
> ksm try import VMAs from one task per loop.
> 
> So add new attribute "mode"
> Two passible values:
>  - normal [default] - ksm use only madvice
>  - always [new]     - ksm will search vma over all processes memory and
>                       add it to the dedup list

Do you have any numbers for how much difference this change makes with
various different workloads?