Re: [RESEND] [PATCH] readahead:add blk_run_backing_dev

[Wu Fengguang <fengguang.wu@intel.com>]

On Mon, Jun 29, 2009 at 10:43:48PM +0800, Ronald Moesbergen wrote:
> 2009/6/29 Wu Fengguang <fengguang.wu@intel.com>:
> > On Mon, Jun 29, 2009 at 09:13:27PM +0800, Wu Fengguang wrote:
> >> On Mon, Jun 29, 2009 at 09:04:57PM +0800, Vladislav Bolkhovitin wrote:
> >> > Wu Fengguang, on 06/29/2009 04:54 PM wrote:
> >> > >
> >> > > Why not 2.6.30? :)
> >> >
> >> > We started with 2.6.29, so why not complete with it (to save additional
> >> > Ronald's effort to move on 2.6.30)?
> >>
> >> OK, that's fair enough.
> >
> > btw, I backported the 2.6.31 context readahead patches to 2.6.29, just
> > in case it will help the SCST performance.
> >
> > Ronald, if you run context readahead, please make sure that the server
> > side readahead size is bigger than the client side readahead size.
> 
> I tried this patch on a vanilla kernel and no other patches applied,
> but it does not seem to help. The iSCSI throughput does not go above
> 60MB/s. (1GB in 17 seconds). I have tried several readahead settings
> from 128KB up to 4MB and kept the server readahead at twice the client
> readahead, but it never comes above 60MB/s. This is using SCST on the

OK, thanks for the tests anyway!

> serverside and openiscsi on the client. I get much better throughput
> (90 MB/s) when using the patches supplied with SCST, together with the

What do you mean by "patches supplied with SCST"?

> blk_run_backing_dev readahead patch.

Thanks,
Fengguang