Re: Time sliced CFQ io scheduler

Giuliano Pochini
2004-12-04T16:06:21Z

On Thu, 2 Dec 2004 15:41:34 +0100
Jens Axboe <axboe@suse.de> wrote:

> > > Case 4: write_files, random, bs=4k
> >
> > Just a thought... in this test the results don't look right. Why
> > aggregate bandwidth with 8 clients is higher than with 4 and 2 clients ?
> > In the cfq test with 8 clients aggregate bw is also higher than with
> > a single client.
>
> I don't know what happens with the 4 client case, but it's not that
> unlikely that aggregate bandwidth will be higher for more threads doing
> random writes, as request coalesching will help minimize seeks.

In order to keep the probabilty that requests get coalesced constant, the
size of the test file should be multiple of the number of clients.

--
Giuliano.