Re: ext4 data=writeback performs worse than data=ordered now

Wu Fengguang
2011-12-14T14:13:22Z

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On Wed, Dec 14, 2011 at 10:00:25PM +0800, Wu Fengguang wrote:
> > The worst case happens for the USB key, where both old/new kernels
> > see ~10% worse performance for data=writeback.
>
> > ext4 ext4:wb
> > ------------------------ ------------------------
> > 6.20 -10.6% 5.54 fat/UKEY-thresh=100M/ext4-1dd-1-3.2.0-rc3-pause6+
>
> Some more comparison numbers for the above worst case.
>
> I don't see obvious differences from the balance_dirty_pages graphs,

Ah there seem to be many more blocks in write_begin(), indicated by
the more negative pause times in the attached second graph.

Thanks,
Fengguang

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