HIGH SYS CPU usage

[Praveen Bezawada]

Hi
We are running java1.3 with informix. sar output shows high sys (24-28) when compared user (65-70). I have checked through glance, system calls
sigsetstatemask,revform,semop,read,write,select,stat64 are some of the heavily used one..
Tusc shows that except semop remaining are being called by java process and semop is mainly being called from informix processes.
Apart from application processes,midaemon and vxfd are high CPU users.
Now the task is to reduce sys usage. What could be potential issues in our case.
Thanks in advance.
...BPK...

[Bill McNAMARA_1]

You have installed all the prerequisite software.

Read the release notes and install ALL patches and dependants.


Later,
Bill

[Chris Vail]

We got similar results when a user loaded up a 32 processor V-class machine with more than 3 million 8k files. Every time the O/S traversed
the directory where these files were, it thrashed. Sure, the computer could handle it,
but a directory is basically a flat file, and not terribly efficient. Deleting the files (with rm *) took 3 and a half days. But once the files were gone, the system utilization
dropped back below 5%. You might check to see
if your system has one or more directories with a LOT of small files.


Chris

[Wodisch]

Hello,

I second what Chris already wrote: seen that a lot in the informix area.
Use "sar -a" (IIRC) and look after the columns "iget" (Inode got per second), "namei" (names converted to their resp. inodenumbers), and "dirbk" (directory blocks processed per second). If you have too many "dirbk/s" then your system slow down dramatically (due to making dozens of megabytes of I/O only for those directories).

HTH,
Wodisch

[Praveen Bezawada]

Hi
Thanks for your responses.
We have couple of directories( 2 in all ) with 20000 files.
And the sar -a shows on average
iget namei dirbk
25 957 1817

Any comments on this ..

...BPK..

[Steven Gillard_2]

IMHO 25% of total cpu usage dedicated to system is not *that* high, especially with lots of IO bound applications.

If you can reduce the number of files in those large directories, I suggest you do so. Also check for other directories which may not have so many files in them now, but have in the past so they are still overly large. Remember, directories don't shrink when files are removed and this can cause performance problems.

Another cause of high sys cpu usage is memory starvation. If you system is paging the sys cpu% will definitely increase.

Regards,
Steve

[Jason VanDerMark]

You may also just for grins check to see if you have any runaway cron processes. We have seen high system numbers when a few crons were spawned on top of each other. This was generally for cleanup scripts that did not finish in the time allotted and as such a second,third, so on cron was spawned. Gzip, rm, and mv processes are huge consumers of system calls. Hope this is helpful.

Regards,
Jason V.