linux-kernel - Re: drm/radeon spamming alloc_contig

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Message-ID: <9f2aa4e4-d7d5-e24f-112e-a4b43f0a0ccc@suse.cz>
Date:   Thu, 1 Dec 2016 08:43:40 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Michal Hocko <mhocko@...nel.org>,
        "Robin H. Johnson" <robbat2@...too.org>
Cc:     Michal Nazarewicz <mina86@...a86.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        dri-devel@...ts.freedesktop.org, Joonsoo Kim <js1304@...il.com>
Subject: Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy

On 12/01/2016 08:21 AM, Michal Hocko wrote:
> Forgot to CC Joonsoo. The email thread starts more or less here
> http://lkml.kernel.org/r/20161130092239.GD18437@dhcp22.suse.cz
>
> On Thu 01-12-16 08:15:07, Michal Hocko wrote:
>> On Wed 30-11-16 20:19:03, Robin H. Johnson wrote:
>> [...]
>> > alloc_contig_range: [83f2a3, 83f2a4) PFNs busy
>>
>> Huh, do I get it right that the request was for a _single_ page? Why do
>> we need CMA for that?

Ugh, good point. I assumed that was just the PFNs that it failed to migrate 
away, but it seems that's indeed the whole requested range. Yeah sounds some 
part of the dma-cma chain could be smarter and attempt CMA only for e.g. costly 
orders.