Re: ext4 write performance regression in 3.6-rc1 on RAID0/5

[NeilBrown]

On Wed, 22 Aug 2012 11:57:02 +0800 Yuanhan Liu <yuanhan.liu@xxxxxxxxxxxxxxx>
wrote:

>  
> -#define NR_STRIPES		256
> +#define NR_STRIPES		1024

Changing one magic number into another magic number might help your case, but
it not really a general solution.

Possibly making sure that max_nr_stripes is at least some multiple of the
chunk size might make sense, but I wouldn't want to see a very large multiple.

I thing the problems with RAID5 are deeper than that.  Hopefully I'll figure
out exactly what the best fix is soon - I'm trying to look into it.

I don't think the size of the cache is a big part of the solution.  I think
correct scheduling of IO is the real answer.

Thanks,
NeilBrown

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