Re: deadline ALWAYS default for dasd devices(s390) ?

[Xose Vazquez Perez]

On 05/05/2010 09:52 AM, Stefan Weinhuber wrote:

hi,

> At the time this change was made we had the problem that the
> default scheduler chosen by the distributions resulted in
> bad performance for DASD devices.

Have you done recently new cfq vs. deadline tests, in z/VM
and LPAR ?

> I agree that hard coding this choice into the driver is not pretty,
> but it is pragmatic. 

It's awful. Easier and simpler from user space: /sys/block/dasdX/queue/scheduler

> Some generic mechanism for setting driver specific
> defaults would be nicer, but I doubt that many other drivers would
> actually benefit from such an interface.

see s390-tools-1.8.4/etc/udev/rules.d/60-readahead.rules
That's the way to do it.

-thanks-

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