So how do you set /proc/sys/vm/bdflush so that it remains from IPL to IPL?
Ihno Krumreich
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Sent by: Linux on To
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<[EMAIL PROTECTED] cc
IST.EDU>
Subject
Re: Linux LPAR - how to drop
09/29/2004 03:00 caching
AM
Please respond to
Linux on 390 Port
<[EMAIL PROTECTED]
IST.EDU>
On Thu, Sep 16, 2004 at 07:04:52PM -0400, David Boyes wrote:
> > We are on STK V2X DASD array. We can do very well without Linux adding
> > further caching. Is there a way to tell Linux not to cache the DASD?
>
> AFAIK, there's no way to turn caching completely off in Linux. You can
> reduce the amount of storage Linux uses for caching by reducing the size
> of the LPAR (which will have other negative effects), but there still
> will be some caching going on.
Thats true.
But you can influence the cache behaviour.
I use the following parameters for /proc/sys/vm/bdflush on a 2.4.21 Kernel:
s390z06:/proc/sys/vm # uname -a
Linux s390z06 2.4.21-250-default #1 SMP Wed Sep 22 09:03:27 UTC 2004 s390x
unknown
s390z06:/proc/sys/vm # cat bdflush
5 5000 0 0 100 500 80 5 0
The parameter have the following meening:
5 - start writing if more than 5% of the buffers are dirty
5000 - maximum number of buffer to write in one wakeup
0 - dummy
0 - dummy
100 - number of ticks for wakeup (if HZ is 100 this means 1 sec)
500 - number of ticks a buffer may wait before written
80 - start synchronous write if more than 80% of the buffers are dirty
5 - dummy
0 - dummy
With these parameters the system starts writing earlier and I/O peaks
happen
less often.
to view the result start vmstat 5 500 and look for the coloums bi and bo
Ihno
--
"Never trust a computer you can lift."
--
Ihno Krumreich [EMAIL PROTECTED]
SuSE Linux AG Projectmanager S390 & zSeries
Maxfeldstr. 5 +49-911-74053-439
D-90409 N�rnberg http://www.suse.de
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