Re: linux 3.1 issue: bdi dirty threshold goes mad

From: Wu Fengguang
Date: Mon Oct 31 2011 - 04:33:16 EST

On Fri, Oct 28, 2011 at 06:58:22AM +0800, Wu Fengguang wrote:
> Hi,
> FYI, I find bdi dirty threshold madness in the newly released v3.1
> according to the gray lines in the attached graphs, which are for
> these test cases:
> 3G-UKEY-HDD/ext4-1dd-4k-8p-2948M-20:10-3.1.0-vanilla+
> 3G-UKEY-HDD/xfs-10dd-4k-8p-2948M-20:10-3.1.0-vanilla+
> 3G-UKEY-HDD/xfs-1dd-4k-8p-2948M-20:10-3.1.0-vanilla+
> It's basically doing concurrent dd's to a USB key and a hard disk.
> Don't know what's going wrong, but at least should be bisectable..

It seems to depend on kernel builds: the problem disappears in the
newly compiled kernels. This makes it pretty hard to catch the root

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