Messages in this thread | | | Date | Mon, 10 Nov 2003 20:28:19 -0800 | From | Andrew Morton <> | Subject | Re: 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/
| |