linux-kernel - Re: page allocator bug in 3.16?

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Message-ID: <542543D8.8020604@vmware.com>
Date:	Fri, 26 Sep 2014 12:45:44 +0200
From:	Thomas Hellstrom <thellstrom@...are.com>
To:	Chuck Ebbert <cebbert.lkml@...il.com>
CC:	Peter Hurley <peter@...leysoftware.com>,
	Mel Gorman <mgorman@...e.de>, Shaohua Li <shli@...nel.org>,
	Rik van Riel <riel@...hat.com>,
	"Maarten Lankhorst" <maarten.lankhorst@...onical.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, Ingo Molnar <mingo@...nel.org>,
	Hugh Dickens <hughd@...gle.com>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: page allocator bug in 3.16?

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....

/Thomas

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