Subject: Re: I/O issues, iowait problems, 2.4 v 2.6
From: Paul Venezia <pvenezia@jpj.net>
To: Andrew Morton <akpm@osdl.org>
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <20031110202819.7e7433a8.akpm@osdl.org>
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> 
> Well that's nice and simple.  Could you please run `vmstat 1' during that
> big `dd'?  Wait for everything to achieve steady state, send us twenty
> lines of the vmstat trace?

I'd pulled this before, here's the output.

> > 
> >  I'd done bonnie++ i/o tests already, and except for an apparent NPTL issue on the per char,
> >  the block i/o numbers were fine; no abnormal results whatsoever. In fact, block r/w
> >  numbers were improved compared to 2.4.22. Now that I'm looking for it, however, I 
> >  do note extremely elevated iowait numbers during a bonnie++ run. Something in the MPT
> >  modules?
> 
> Greater than 90% I/O wait is to be expected in these tests.  What is of
> interest is the overall bandwidth.2.5 megabytes per second is very broken.

Definitely. I should have noted that the 2.4.22 tests on that dd came
back in 23.607s, the 2.6.0 tests hadn't returned for over 4 minutes.

> 2.5 megabytes per second is very
> broken.  I have a 53c1030 box here which uses the MPT fusion driver and it
> happily does 50MB/sec to a single disk, but I guess that's a different
> setup.

This is a 53C1030 with a RAID1 mirror. Now that I think about it, I did
the >2GB bonnie tests on a single disk, no mirror. I'll rerun the i/o
tests with this setup and then remove the mirror and see what happens.

-Paul

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