Qustion about being "Giant-locked"

Artem Koutchine matrix at itlegion.ru
Tue Apr 6 01:14:44 PDT 2004

>From: "Andy Farkas" <andyf at speednet.com.au>
>Sent: Tuesday, April 06, 2004 11:56 AM
> On Tue, 6 Apr 2004, Xin LI wrote:
> > On Tue, Apr 06, 2004 at 11:03:13AM +0400, Artem Koutchine wrote:
> > > While booting i see many drivers marked
> > > as [Giant-locked].
> > > Is being Giant-locked good or bad what are the
> > > implications?
> > It's not good if you have a computer with multiple processors.
> I have a box with 4 ppro-200 cpus. It has 4 adaptec eisa scsi controllers,
> each controlling 2 disks. All 8 disks are in the same vinum raid-5 volume.
> I have a large (1.5gig) file on this volume.
> This is what happens when I run md5 on this file 4 times concurrently:
> As you can see, only 8% of all cpus are being used to calculate the md5s.
> At least 2 cpus are constantly idle.
> ahc5: [GIANT-LOCKED]
> atkbd0: [GIANT-LOCKED]

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.


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