Solaris 2.3 "fsflush" ???

[Geoff D. Gibbs]

HELP !

I'm currently running Solaris 2.3 patched to 101318-70. The system has 128mb
of memory, running on a Sparc-20.

What is happening is, "fsflush" is running and using up between 50-80% of the
CPU. My questions are:

What is fsflush?
Is this a bug?
How can I fix this?

P.S. I'm running NIS+, and NFS server to another Sparc-20 and about 30 pc's.

Thanks, Geoff Gibbs

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* Geoff D. Gibbs __|__ ggi...@jeppden.com *
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[Sam Sexton]

Geoff D. Gibbs writes:
> I'm currently running Solaris 2.3 patched to 101318-70. The system has 128mb
> of memory, running on a Sparc-20.
>
> What is happening is, "fsflush" is running and using up between 50-80% of the
> CPU. My questions are:
>
> What is fsflush?
> Is this a bug?
> How can I fix this?

The following notes refer to 2.4, but will probably help you - the book evolved
from a previous Sun white paper: Sun Performance Tuning Overview.

flsflush is the process that writes out updates to disk, and its rate of
activity can be controlled by the tune_t_fsflushr and autoup parameters as
shown - I suggest that you play with these and see if they have any impact -
but any changes you make are likely to delay the hard writing of updates.

You should also read the Performance and Accounting section (Part II) of
SunOS 5.x Adminstering Security, Performance and Accounting.

Good luck!

The bible is Sun Performance and Tuning by Adrian Cockcroft, published
by Prentice Hall at GBP38.95, ISBN 0-13-149642-5.

Further notes below as they turn up:

1. tune:tune_t_fsflushr vs autoup:
These two are related and best explained by way of the following
example:

if autop=300 and flushr=30, then fsflush is invoked every 30
seconds and will flush any outstanding writes in the first 10th
(30/300) of memory; this naturally excludes writes forced by fsync.
The next time (30 secs later) it's invoked, it looks at the next
10th of memory, and so on. Therefore the worst case is that an
update might not be written out for 5 minutes (300 secs).

However, if more than 384k is updated, that will be written out
regardless of the above rules.

2. In 2.4, when running tasks from the console, the interactive
scheduler gives a higher priority to the task whose window has the
mouse focus.

3. Tools: proctool, top, truss, perfmeter, sar, vmstat, iostat

Thanks to Phil Harman at the Sun office in Sale for the first two points
above.
--
Sam Sexton Phone: +44 1203 256562
Sam@leofric@demon.co.uk Fax: +44 1203 555203
Reuters Ltd, Coventry, UK