linux-kernel - mm/cma.c: High latency for cma allocation

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Date:   Mon, 18 Mar 2019 12:58:28 +0000
From:   Pankaj Suryawanshi <pankaj.suryawanshi@...fochips.com>
To:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "minchan@...nel.org" <minchan@...nel.org>,
        Michal Hocko <mhocko@...nel.org>
CC:     Kirill Tkhai <ktkhai@...tuozzo.com>
Subject: mm/cma.c: High latency for cma allocation

Hello,

I am facing issue of high latency in CMA allocation of large size buffer.

I am frequently allocating/deallocation CMA memory, latency of allocation is very high.

Below are the stat for allocation/deallocation latency issue.

(390100 kB),  latency 29997 us
(390100 kB),  latency 22957 us
(390100 kB),  latency 25735 us
(390100 kB),  latency 12736 us
(390100 kB),  latency 26009 us
(390100 kB),  latency 18058 us
(390100 kB),  latency 27997 us
(16 kB), latency 560 us
(256 kB), latency 280 us
(4 kB), latency 311 us

I am using kernel 4.14.65 with android pie(9.0).

Is there any workaround or solution for this(cma_alloc latency) issue ?

Regards,
Pankaj
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