Re: bad performance with SSD since kernel version 2.6.32

[Robert Hancock <hancockrwd@gmail.com>]

On 02/20/2010 07:28 AM, Benjamin S. wrote:
>
> Hello list,
>
> I have a Super Talent Ultradrive GX MLC 64GB SSD and an Intel
> DH55HC board with H55 chipset. Processor is an Intel Core i5-661.
>
> Since 2.6.32 the sequentiell read performance of the ssd is bad:
>
> # dd if=/dev/sda of=/dev/zero bs=1M count=300
> 300+0 records in
> 300+0 records out
> 314572800 bytes (315 MB) copied, 4.61777 s, 68.1 MB/s
>
> Same results with other blocksizes (e.g tested with 4K).
>
>
> With 2.6.31.7 the same hardware is able to read with about
> 190MB/s.
>
>
> The normal hard drive reads with both kernel versions with about 100MB/s.
>
>
> Does somebody have an idea what I can test before I have to bisect
> it?

Could be some kind of block layer or IO scheduler behavior change.. you 
could try testing after doing:

echo noop > /sys/block/sda/queue/scheduler

or

echo deadline > /sys/block/sda/queue/scheduler

and see if that affects the speed..