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

[Stefan Weinhuber]

Heiko Carstens wrote:
> On Mon, Apr 26, 2010 at 02:34:16PM +0200, Xose Vazquez Perez wrote:
> > hi,
> >
> > why is it FORCED ? bypassing a GLOBAL setting and also the kernel command line !!!
>
> Horst, Stefan W. or Stefan H. should be able to answer your question.

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.
I don't know what options were considered back then, but
I think that having the device driver set a driver specific default
is better than forcing the whole system to use 'our' scheduler.

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


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