Re: Slow file transfer speeds with CFQ IO scheduler in some cases

[Jeff Layton]

On Tue, 11 Nov 2008 14:36:07 -0500
Jeff Moyer <jmoyer@xxxxxxxxxx> wrote:

> Jens Axboe <jens.axboe@xxxxxxxxxx> writes:
> 
> > OK, that looks better. Can I talk you into just trying this little
> > patch, just to see what kind of performance that yields? Remove the cfq
> > patch first. I would have patched nfsd only, but this is just a quick'n
> > dirty.
> 
> I went ahead and gave it a shot.  The updated CFQ patch with no I/O
> context sharing does about 40MB/s reading a 1GB file.  Backing that
> patch out, and then adding the patch to share io_context's between
> kthreads yields 45MB/s.
> 

Here's a quick and dirty patch to make all of the nfsd's have the same
io_context. Comments appreciated -- I'm not that familiar with the IO
scheduling code. If this looks good, I'll clean it up, add some
comments and formally send it to Bruce.

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