Re: poor domU VBD performance.

[Nivedita Singhvi <niv@us.ibm.com>]

Kurt Garloff wrote:

> Hi Niv,
> 
> On Thu, Mar 31, 2005 at 08:27:30AM -0800, Nivedita Singhvi wrote:
> 
>>Although the usual answer for what scheduling algorithm is
>>best is almost always "depends on the workload", it was
>>suggested to me that the cfq was still the best option to
>>go with. What do people feel about that? (Or is AS going
>>to remain default?).
> 
> 
> This is a different dicussion.

Yes, I did change the subject a little ;).

> But, yes, I would agree that CFQ (v3) is the best default choice.

Yep, even though some of the complications in the Xen
environment (as you point out below) will have to be addressed.

> Jens, should we maybe make sure that the blockback driver does use 
> different (fake) UIDs for the domains that it serves to provide 
> the fairness between them. Next step would be to allow to tweak 
> IO priorities. Or, to make it more general, add a parameter (call
> it uid), that a block driver can pass down to the IO scheduler
> and that would normally be current->uid but may be set differently?


> It's part of 2.6.11.
> garloff@tpkurt:~ [0]$ cat /sys/block/hda/queue/scheduler
> noop anticipatory deadline [cfq]

I just saw Jens' reply as well. This is much goodness :).
Very handy indeed!

thanks,
Nivedita