linux-kernel - Re: [PATCH v2 01/12] mm: Assign id to every memcg-aware shrinker

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Message-Id: <201804182332.FAC65178.FLVJFMSOtHOFQO@I-love.SAKURA.ne.jp>
Date:   Wed, 18 Apr 2018 23:32:42 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     ktkhai@...tuozzo.com, willy@...radead.org, wei.w.wang@...el.com
Cc:     akpm@...ux-foundation.org, vdavydov.dev@...il.com,
        shakeelb@...gle.com, viro@...iv.linux.org.uk, hannes@...xchg.org,
        mhocko@...nel.org, tglx@...utronix.de, pombredanne@...b.com,
        stummala@...eaurora.org, gregkh@...uxfoundation.org,
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        chris@...is-wilson.co.uk, longman@...hat.com, minchan@...nel.org,
        hillf.zj@...baba-inc.com, ying.huang@...el.com,
        mgorman@...hsingularity.net, jbacik@...com, linux@...ck-us.net,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        willy@...radead.org, lirongqing@...du.com, aryabinin@...tuozzo.com
Subject: Re: [PATCH v2 01/12] mm: Assign id to every memcg-aware shrinker

Kirill Tkhai wrote:
> On 18.04.2018 17:14, Tetsuo Handa wrote:
> > Kirill Tkhai wrote:
> >> The patch introduces shrinker::id number, which is used to enumerate
> >> memcg-aware shrinkers. The number start from 0, and the code tries
> >> to maintain it as small as possible.
> >>
> >> This will be used as to represent a memcg-aware shrinkers in memcg
> >> shrinkers map.
> > 
> > I'm not reading this thread. But is there reason "id" needs to be managed
> > using smallest numbers? Can't we use address of shrinker object as "id"
> > (which will be sparse bitmap, and would be managed using linked list for now)?
> 
> Yes, it's needed to have the smallest numbers, as next patches introduce
> per-memcg bitmap containing ids of shrinkers.

If you use sparse bitmap (xbitmap ?), I think you can do it.