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Re: Howto vmstat

 
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BRAGEUL
Frequent Advisor

Howto vmstat

I suppose that i have got a performance problem on my DS25 Tru64 5.1.B . I use vmstat and i note this result (fault value in my case is strong )
root> vmstat 5 3
Virtual Memory Statistics: (pagesize = 8192)
procs memory pages intr
cpu
r w u act free wire fault cow zero react pin pout in sy cs
us sy id
4 209 39 91K 139K 21K 11M 1M 5M 348 2M 0 67 1K 397
3 1 96
3 209 40 91K 139K 21K 2 15 23 0 27 0 399 4K 1K
55 3 42
3 209 40 91K 139K 21K 0 0 0 0 0 0 404 4K 1K
57 3 40

What does it mean 21K in fault value. Is this value normal.

Can you Help me to describe this result
My config :
DS25 mono Proc With 2Go RAM and 2 Database Instance Oracle 9i (50 Users).
15 REPLIES 15
Michael Schulte zur Sur
Honored Contributor
Solution

Re: Howto vmstat

Hi,

to me it looks like, the 21k belong to the memory wire and fault is 11m.

btw, the first row is the accumulation since boot time.

greetings,

Michael
BRAGEUL
Frequent Advisor

Re: Howto vmstat

Thank for your response,

But how can i suspect on my server a performance problem about (memory, Cpu...)
What are the main critical value of result of command like vmstat or collect or sys_check.

Bests Regards
Michael Schulte zur Sur
Honored Contributor

Re: Howto vmstat

Hi,

collect I don't know, but sys_check creates a html file and makes suggestions, if values are too low or high. Also you can watch the system with top and monitor.
One important value is page out. This should not happen on a regular basis becauses it indicates a memory shortage and makes the system slow.

From what I have seen from the vmstat, your system isn't heavily burdoned, but it is of course only a show period.

How long has the machine been up?

Michael
Hein van den Heuvel
Honored Contributor

Re: Howto vmstat


That actually looks healthy from a systme perspective. A decent amount of user time, modest system time, reasonable interupt-systemcalls-contecswitch ratios, Free memory, no paging (during vmstat!).

The only worrying component in your post is the opening line: "I suppose that i have got a performance problem". Could it be that all is well, or are your users complaining?

If Oracle is the bulk of your work, then even without serious investigation you may want to consider to give more memory to Oracle. You seem to have 1GB free ?! How big are the SGA's for the 2 instances? Double in size?!

For serious investigations be sure to run Oracle statspack over a representative period of production time and share hightlights of the report(s).

Regards,
Hein.
BRAGEUL
Frequent Advisor

Re: Howto vmstat

Hi Hein,

You told me that you have seen 1Go free of memory . Did you see this value in vmstat stat result ? so is it the free value 139K in vmstat result ? so what is the mathematique formul to obtain 1Go with a result of 139K ?

....
Is oracle StatPack is a additional product (free or not) ?

Thanks
Johan Brusche
Honored Contributor

Re: Howto vmstat


A standard page in Tru64 contains 8192 octets(bytes). So the 139Koctets under vmstat's "free" column gives 139*1024*8192=1166016512octets=1,16 GB

Cordialement,
Johan.

_JB_
Hein van den Heuvel
Honored Contributor

Re: Howto vmstat


Right.

For an other, more detailed, view on (Physical) memory try: vmstat -P

It show some pages to bytes info, and is a nice way to see 'GH' memory should you ever decide to use that Oracle enhancer.

(sysconfig -q vm | grep gh)

Hein.
BRAGEUL
Frequent Advisor

Re: Howto vmstat

Hi,

This is a result of vmstat when my server in full used.

is there any strong value ?
Hein van den Heuvel
Honored Contributor

Re: Howto vmstat

Ah, that's a different picture.
Now you are almost out of memory.

It is not as bad as it sounds because the ubc had grown to 800M (97098 pages) and can readily be trimmed down if more memory pressure occurs. Considering that this is an Oracle box, you may want to limit max_ubc to say 20% (still 400MB) and give the memory directly to Oracle (SGA) wihout it having to fight the ubc. Also, try GH or bigpages !?


Overall it still looks like a reasonably happy system.

You are doing a little more system time then I would like to see. Do you have timed_statistics on for the Oracle instances? Are you actually collecting stats?
What level?
SQL> show parameter statistics

You do NOT want level TYPICAL as it seems to add little value but uses a lot of system time through getrusage calls. Try:
alter system set statistics_level=BASIC;

You may also want to create a time-device to allow oracle (after restart) to read the time mapped from memory instead of needing the gettimeofday system call:
mknod /dev/timedev c 15 0

Cheers,
Hein.