linux-kernel - [Regression] mm: Huge swapout performance regression on recent kernels

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Message-Id: <201007201507.31851.a1426z@gawab.com>
Date:	Tue, 20 Jul 2010 15:07:31 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	linux-kernel@...r.kernel.org
Subject: [Regression] mm: Huge swapout performance regression on recent kernels

I have noticed a big swapout performance regression on recent kernels using 
the following testcase:

swapon /dev/md0 (raid0)
mount none /dev/shm -t tmpfs -o size=10G 
cat /dev/full > /dev/shm/tst.dmp

Kernel starts to swapout at full speed after filling physical ram.
Then, kernel progressively slows down swapout after crossing the ~3G VM 
threshold, compounding at over 50% slowdown when reaching the 10G tmpfs 
limit.

Has this been fixed?

Thanks!

--
Al

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