Re: [RFC] Block IO Controller V2 - some results

Alan D. Brunelle
2009-11-17T16:44:59Z

On Tue, 2009-11-17 at 17:17 +0100, Corrado Zoccolo wrote:
> Hi Vivek,
> the performance drop reported by Alan was my main concern about your
> approach. Probably you should mention/document somewhere that when the
> number of groups is too large, there is large decrease in random read
> performance.
>
> However, we can check few things:
> * is this kernel built with HZ < 1000? The smallest idle CFQ will do
> is given by 2/HZ, so running with a small HZ will increase the impact
> of idling.

FYI:

CONFIG_NO_HZ=y
CONFIG_HZ_1000=y
CONFIG_HZ=1000