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

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Date:	Thu, 25 Sep 2014 14:35:55 -0500
From:	Chuck Ebbert <cebbert.lkml@...il.com>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Mel Gorman <mgorman@...e.de>, Shaohua Li <shli@...nel.org>,
	Rik van Riel <riel@...hat.com>,
	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	Thomas Hellstrom <thellstrom@...are.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 Thu, 25 Sep 2014 14:55:02 -0400
Peter Hurley <peter@...leysoftware.com> wrote:

> After several days uptime with a 3.16 kernel (generally running
> Thunderbird, emacs, kernel builds, several Chrome tabs on multiple
> desktop workspaces) I've been seeing some really extreme slowdowns.
> 
> Mostly the slowdowns are associated with gpu-related tasks, like
> opening new emacs windows, switching workspaces, laughing at internet
> gifs, etc. Because this x86_64 desktop is nouveau-based, I didn't pursue
> it right away -- 3.15 is the first time suspend has worked reliably.
> 
> This week I started looking into what the slowdown was and discovered
> it's happening during dma allocation through swiotlb (the cpus can do
> intel iommu but I don't use it because it's not the default for most users).
> 
> I'm still working on a bisection but each step takes 8+ hours to
> validate and even then I'm no longer sure I still have the 'bad'
> commit in the bisection. [edit: yup, I started over]
> 

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
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