Messages in this thread | | | From | Antonio Larrosa Jiménez <> | Subject | Re: iowait problems on 2.6, not on 2.4 | Date | Fri, 28 May 2004 15:16:41 +0200 |
| |
On Thursday 27 May 2004 05:52, you wrote: > Antonio Larrosa Jiménez <antlarr@tedial.com> wrote: > > My next test will be to do the "dd tests" on one of the internal hard > > disks and use it for the data instead of the external raid. > > That's a logical next step. The reduced read bandwith on the raid array > should be fixed up before we can go any further. I don't recall any > reports of qlogic fc-scsi performance regressions though.
Ok, let's analyze that first.
The dd tests gave the following results:
ext3 on the internal scsi HD: 2.4.21: writing : 1m14s reading : 1m2s reading+writing : 2m16s 2.6.4: writing : 1m19s reading : 59s reading+writing : 2m24s
reiserfs on the internal scsi HD: 2.4.21: writing : 1m15s reading : 1m1s reading+writing : 2m22s 2.6.4: writing : 1m19s reading : 1m reading+writing : 2m25s
ext3 on the raid using qlogic fc-scsi: 2.4.21: writing : 30s reading : 51s reading+writing : 1m29s 2.6.4: writing : 28s reading : 1m26s reading+writing : 2m19s
reiserfs on the raid using qlogic fc-scsi: 2.4.21: writing : 37s reading : 52s reading+writing : 1m37s 2.6.4: writing : 25s reading : 1m27s reading+writing : 2m3s
All the tests were made 3 times, and the average taken. In the cases where there was too much variance, I repeated the tests some more times.
All the tests used 2Gb reads/writes (. I tried to make 8Gb reads/writes too, but they got up to a minute variance (maybe the HD slowed itself down due to temperature issues sometimes? I really don't know why this happened, but in any case, I couldn't make reliable tests with files of that size).
So basically, there's no difference between 2.4.21 and 2.6.4 when using the internal HD, but 2.6.4 is much slower when using the raid. What I found strange is that writing to that raid is a bit faster on 2.6.4 while reading is much slower, which I suppose is what makes the difference.
So yes, I suppose there's a regression on the qlogic fc-scsi module.
Btw, the tests I timed were:
count=2048 write() { dd if=/dev/zero of=x bs=1M count=$count ; sync } read() { dd if=x of=/dev/null bs=1M count=$count } readwrite() { dd if=x of=y bs=1M count=$count ; sync }
In the case of read, I did the sync just before and after the timing, but didn't include the sync inside the timed test.
As I said in my other mail, I can test any patch if needed.
Greetings and thanks for any help
-- Antonio Larrosa Tecnologias Digitales Audiovisuales, S.L. http://www.tedial.com Parque Tecnologico de Andalucia . Málaga (Spain) - 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/
| |