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FromHeinz Mauelshagen <>
SubjectHELP!! Serious stability problems with Linux! Where to go from here?
DateSun, 28 Jun 1998 11:04:36 METDST
> From: "Jeremy Domingue" <jer@hughes.net>
> Date: Sat, 27 Jun 1998 17:42:53 -0700
> Subject: HELP!! Serious stability problems with Linux! Where to go from here?


Just some ideas to help you...


You mentioned 2 IMHO _main_ facts:

 - using aic7xxx driven SCSI devices
 - _very_ busy server


Please try to configure tag queue depth down to below 5
for all scsi devices _and_ don't use the actual > 5.0.13 aic7xxx driver!
You can fetch 5.0.13 from kernel 2.1.102 for egg.
BTW: you can limit queue depth with lilo's append like

append = "aic7xxx=tag_info:{{4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4}}"


Please try a patch in /usr/src/linux/fs/buffer.c in function grow_buffers()
which _really_ limits the size of the buffer cache.
(yes i know that some people say this isn't stable too, but for me
it runs and runs and ...)

A simple testhack can be:

        if ( buffermem > BufferMemSizeInBytes) return 0;
at the top of grow_buffers().
Replace BufferMemSizeInBytes with the value you like.
With your RAM size start please start with 64*1024*1024.

I used the first one, because aic7xxx even crashes a single processor
system with queue depth > 4 on a busy system.
The second one avoided instability and _really_ bad performance, because
the actual buffer code doeen't recognize the limits given in
/proc/sys/vm/buffermem and then runs into trouble for sure!
Tell me about (i hope) your success.

Best regards,
Heinz

--

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Systemmanagement Entwicklungsbereich 2           Deutsche Telekom AG
                                                 Entwicklungszentrum Darmstadt
Heinz Mauelshagen                                Otto-Roehm-Strasse 71c
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mge@ez-darmstadt.telekom.de                      64205 Darmstadt
                                                 Germany
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