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SubjectPoor SCSI // reading using 2.2.10-ac4 SMP


I have run iozone locally on my new 18 Go hard disk to check performance.
The Linux machine is a PII 400/128 Mo/SMP/Tekram 390F.

I have quite good results with only one iozone : 17+ Mo/s writing, 15+ Mo/s

Now, I can see really bad performance with 3 iozones running :
17+ Mo/s (cumulated) writing, and 2,7 Mo/s (cumulated) reading. At the time
of reading, both CPU load is nearly null.

If I use a UP kernel (2.2.10-ac4 or 2.2.5) I have 8+ Mo/s reading, which
can be explained (I guess) due to heads movements and seek times.

So, it seems that SMP has big trouble when parrallelizing readings (maybe
a problem with SCSI, I do not know, since I have no IDE on the SMP box).

Thierry Danis
Poste : 53 53

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