Re: A quick fio test (was Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3)

Ingo Molnar
2007-02-27T16:23:12Z

* Avi Kivity <avi@argo.co.il> wrote:

> > yeah - that's what testing on ramdisk (Jens') or on a loopback block
> > device (mine) approximates to a certain degree.
>
> Ramdisks or fully cached loopback return immediately, so cache
> thrashing effects don't show up.

even fully cached loopback schedules the loopback kernel thread - but i
agree that it's inaccurate: hence the 'approximates to a certain
degree'.

> Maybe a device mapper delay target or nbd + O_DIRECT can insert delays
> to make the workload more disk-like.

yeah. I'll hack a small timeout into loopback requests i think. But then
real disk-platter effects are left out ... so it all comes down to
eventually having to try it on real disks too :)

Ingo