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Date: Tue, 6 Apr 2004 19:39:00 +1000 (EST)
From: Andy Farkas <andyf@speednet.com.au>
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Subject: Re: Qustion about being "Giant-locked"
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> I am trying to get your point and i really can't. I just don't see what
> your are trying to say. If you refer to 8% CPU usage then i see that it
> is only 8% because SCSI is the bottleneck. Disk just do not give data
> fast enough to load CPU high. Also, i don't think the do not give
> data fast enough only because of the Giant. I think it is mostly scsi
> and hdd speed problem in this case. Afterall md5 algorithm is not
> too havy on cpu anyway.

What I was trying to point out is that there is hardly any concurrency
with disk drivers on a SMP box.

With 4 controllers, 8 spindles, and 4 cpus to drive them, one would expect
a little bit of concurrency. Instead, the kernel spends most of its time
waiting or blocked, only one disk is accessed at a time, and the cpus stay
idle.

md5 may have been a bad example, but on a slow 200MHz cpu, it can be a
fairly intensive cpu hog.

--

 :{ andyf@speednet.com.au

        Andy Farkas
    System Administrator
   Speednet Communications
 http://www.speednet.com.au/