Re: [PATCH 0/11] Reduce compaction-related stalls and improveasynchronous migration of dirty pages v6

[Andrew Morton]

On Wed, 14 Dec 2011 15:41:22 +0000
Mel Gorman <mgorman@xxxxxxx> wrote:

> Short summary: There are severe stalls when a USB stick using VFAT
> is used with THP enabled that are reduced by this series. If you are
> experiencing this problem, please test and report back and considering
> I have seen complaints from openSUSE and Fedora users on this as well
> as a few private mails, I'm guessing it's a widespread issue. This
> is a new type of USB-related stall because it is due to synchronous
> compaction writing where as in the past the big problem was dirty
> pages reaching the end of the LRU and being written by reclaim.
> 
> Am cc'ing Andrew this time and this series would replace
> mm-do-not-stall-in-synchronous-compaction-for-thp-allocations.patch.
> I'm also cc'ing Dave Jones as he might have merged that patch to Fedora
> for wider testing and ideally it would be reverted and replaced by
> this series.

So it appears that the problem is painful for distros and users and
that we won't have this fixed until 3.2 at best, and that fix will be a
difficult backport for distributors of earlier kernels.

To serve those people better, I'm wondering if we should merge
mm-do-not-stall-in-synchronous-compaction-for-thp-allocations now, make
it available for -stable backport and then revert it as part of this
series?   ie: give people a stopgap while we fix it properly?

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