Re: RFC on io-stalls patch

From: Andrea Arcangeli (andrea@suse.de)
Date: Tue Jul 15 2003 - 05:03:57 EST


On Tue, Jul 15, 2003 at 11:18:38AM +0200, Jens Axboe wrote:
> On Tue, Jul 15 2003, Jens Axboe wrote:
> > > BTW, the contest run times vary pretty wildy. My 3 compiles with
> > > io_load running on 2.4.21 were 603s, 443s and 515s. This doesn't make
> > > the average of the 3 numbers invalid, but we need a more stable metric.
> >
> > Mine are pretty consistent [1], I'd suspect that it isn't contest but your
> > drive tcq skewing things. But it would be nice to test with other things
> > as well, I just used contest because it was at hand.
>
> Oh and in the same spirit, I'll do the complete runs on an IDE drive as
> well. Sometimes IDE vs SCSI shows the funniest things.

this is the first suspect IMHO too. Especially given the way that SCSI
releases the requests.

One more thing: unlike my patch where I forced all drivers to support
elevator-lowlatency (either that or not compile at all), Chris made it
optional when he pushed it into mainline, so now the device driver has
to call blk_queue_throttle_sectors(q, 1) to enable it. Otherwise it'll
run like 2.4.21.

Andrea
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