linux-kernel - Re: [PATCH v2 3/3] percpu: improve allocation success rate for non-GFP

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Message-ID: <20170227170753.GO26504@dhcp22.suse.cz>
Date:   Mon, 27 Feb 2017 18:07:53 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Tahsin Erdogan <tahsin@...gle.com>
Cc:     Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Roman Pen <r.peniaev@...il.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        zijun_hu <zijun_hu@....com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] percpu: improve allocation success rate for
 non-GFP_KERNEL callers

On Mon 27-02-17 09:01:09, Tahsin Erdogan wrote:
> On Mon, Feb 27, 2017 at 7:25 AM, Michal Hocko <mhocko@...nel.org> wrote:
> >         /*
> >          * No space left.  Create a new chunk.  We don't want multiple
> >          * tasks to create chunks simultaneously.  Serialize and create iff
> >          * there's still no empty chunk after grabbing the mutex.
> >          */
> >         if (is_atomic)
> >                 goto fail;
> >
> > right before pcpu_populate_chunk so is this actually a problem?
> 
> Yes, this prevents adding more pcpu chunks and so cause "atomic" allocations
> to fail more easily.

Then I fail to see what is the problem you are trying to fix.

-- 
Michal Hocko
SUSE Labs