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

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Message-ID: <CAAeU0aPGvoYr=dtbRWT3=S5x9HmkUEiGmGWQy0JdFVu3F40N9g@mail.gmail.com>
Date:   Mon, 27 Feb 2017 13:12:11 -0800
From:   Tahsin Erdogan <tahsin@...gle.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Michal Hocko <mhocko@...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

>> Doing preallocations would probably work but not sure if that can be
>> done without
>> complicating code too much. Could you describe what you have in mind?
>
> So, blkg_create() already takes @new_blkg argument which is the
> preallocated blkg and used during q init.  Wouldn't it work to make
> blkg_lookup_create() take @new_blkg too and pass it down to
> blkg_create() (and also free it if it doesn't get used)?  Then,
> blkg_conf_prep() can always (or after a failure with -ENOMEM) allocate
> a new blkg before calling into blkg_lookup_create().  I don't think
> it'll complicate the code path that much.

That makes sense. I will work a patch that does that (unless you are
interested in implementing it yourself).