Messages in this thread | | | Date | Tue, 15 Jul 2003 11:17:30 +0200 | From | Jens Axboe <> | Subject | Re: RFC on io-stalls patch |
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On Tue, Jul 15 2003, Chris Mason wrote: > On Tue, 2003-07-15 at 04:28, Jens Axboe wrote: > > > Definitely, because prepare to be a bit disappointed. Here are scores > > that include 2.4.21 as well: > > > io_load: > > Kernel [runs] Time CPU% Loads LCPU% Ratio > > 2.4.21 3 543 49.7 100.4 19.0 4.08 > > 2.4.22-pre5 3 637 42.5 120.2 18.5 4.75 > > 2.4.22-pre5-axboe 3 540 50.0 103.0 18.1 4.06 > > Huh, this is completely different than io_load on my box (2P scsi, ext3, > data=writeback) > > io_load: > Kernel [runs] Time CPU% Loads LCPU% Ratio > 2.4.21 3 520 52.5 27.8 15.2 3.80 > 2.4.22-pre5 3 394 69.0 21.5 15.4 2.90 > 2.4.22-sync 3 321 84.7 16.2 15.8 2.36 > > Where 2.4.22-sync was the variant I posted yesterday. I don't really > see how 2.4.21 can get numbers as good as 2.4.22-pre5 on the io_load > test, the read starvation with a big streaming io is horrible. > > The data=writeback is changing the workload significantly, I used it > because I didn't want the data=ordered code to flush all dirty buffers > every 5 seconds. I would expect ext3 data=ordered to be pretty > starvation prone in 2.4.21 as well though.
Well maybe it's due to data=writeback? I'm using completely stock options for ext3. You didn't mention tcq depth of your scsi drive, in my experience it's worthless to test io scheduler behaviour using more than a few tags.
> 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.
[1] when the current run completes, I can post them all.
-- Jens Axboe
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