linux-kernel - Re: [PATCH 01/10] mm: Assign id to every memcg-aware shrinker

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Message-ID: <20180326151406.GE10912@bombadil.infradead.org>
Date:   Mon, 26 Mar 2018 08:14:06 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     Vladimir Davydov <vdavydov.dev@...il.com>, viro@...iv.linux.org.uk,
        hannes@...xchg.org, mhocko@...nel.org, akpm@...ux-foundation.org,
        tglx@...utronix.de, pombredanne@...b.com, stummala@...eaurora.org,
        gregkh@...uxfoundation.org, sfr@...b.auug.org.au, guro@...com,
        mka@...omium.org, penguin-kernel@...ove.SAKURA.ne.jp,
        chris@...is-wilson.co.uk, longman@...hat.com, minchan@...nel.org,
        hillf.zj@...baba-inc.com, ying.huang@...el.com,
        mgorman@...hsingularity.net, shakeelb@...gle.com, jbacik@...com,
        linux@...ck-us.net, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 01/10] mm: Assign id to every memcg-aware shrinker

On Mon, Mar 26, 2018 at 06:09:35PM +0300, Kirill Tkhai wrote:
> > AFAIK ida always allocates the smallest available id so you don't need
> > to keep track of bitmap_id_start.
> 
> I saw mnt_alloc_group_id() does the same, so this was the reason, the additional
> variable was used. Doesn't this gives a good advise to ida and makes it find
> a free id faster?

No, it doesn't help the IDA in the slightest.  I have a patch in my
tree to delete that silliness from mnt_alloc_group_id(); just haven't
submitted it yet.