Date:	Fri, 26 Sep 2014 08:28:19 -0400
From:	Rob Clark <robdclark@...il.com>
To:	Thomas Hellstrom <thellstrom@...are.com>
Cc:	Chuck Ebbert <cebbert.lkml@...il.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Hugh Dickens <hughd@...gle.com>,
	Linux kernel <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	linux-mm <linux-mm@...ck.org>, Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Shaohua Li <shli@...nel.org>, Ingo Molnar <mingo@...nel.org>
Subject: Re: page allocator bug in 3.16?

On Fri, Sep 26, 2014 at 6:45 AM, Thomas Hellstrom <thellstrom@...are.com> wrote:
> On 09/26/2014 12:40 PM, Chuck Ebbert wrote:
>> On Fri, 26 Sep 2014 09:15:57 +0200
>> Thomas Hellstrom <thellstrom@...are.com> wrote:
>>
>>> On 09/26/2014 01:52 AM, Peter Hurley wrote:
>>>> On 09/25/2014 03:35 PM, Chuck Ebbert wrote:
>>>>> There are six ttm patches queued for 3.16.4:
>>>>>
>>>>> drm-ttm-choose-a-pool-to-shrink-correctly-in-ttm_dma_pool_shrink_scan.patch
>>>>> drm-ttm-fix-handling-of-ttm_pl_flag_topdown-v2.patch
>>>>> drm-ttm-fix-possible-division-by-0-in-ttm_dma_pool_shrink_scan.patch
>>>>> drm-ttm-fix-possible-stack-overflow-by-recursive-shrinker-calls.patch
>>>>> drm-ttm-pass-gfp-flags-in-order-to-avoid-deadlock.patch
>>>>> drm-ttm-use-mutex_trylock-to-avoid-deadlock-inside-shrinker-functions.patch
>>>> Thanks for info, Chuck.
>>>>
>>>> Unfortunately, none of these fix TTM dma allocation doing CMA dma allocation,
>>>> which is the root problem.
>>>>
>>>> Regards,
>>>> Peter Hurley
>>> The problem is not really in TTM but in CMA, There was a guy offering to
>>> fix this in the CMA code but I guess he didn't probably because he
>>> didn't receive any feedback.
>>>
>> Yeah, the "solution" to this problem seems to be "don't enable CMA on
>> x86". Maybe it should even be disabled in the config system.
> Or, as previously suggested, don't use CMA for order 0 (single page)
> allocations....

On devices that actually need CMA pools to arrange for memory to be in
certain ranges, I think you probably do want to have order 0 pages
come from the CMA pool.

Seems like disabling CMA on x86 (where it should be unneeded) is the
better way, IMO

BR,
-R


> /Thomas
>
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