lkml.org 
[lkml]   [2003]   [Nov]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: I/O issues, iowait problems, 2.4 v 2.6
Paul Venezia <pvenezia@jpj.net> wrote:
>
> > As next steps I'd suggest that you log into the server and do
> >
> > time (dd if=/dev/zero of=x bs=1M count=2048 ; sync)
> >
> > and
> >
> > time (dd if=x of=/dev/null bs=1M count=2048 ; sync)
> >
> > (this assumes that the machine has less that 2G of memory, to avoid caching
> > effects).
>
> The raw file read/write is the ticket. The box tightens right up at 100% iowait.

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 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. 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.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:58    [W:0.073 / U:0.116 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site