Setting kernel params after Mem and CPU upgrade?

[Kalin Evtimov]

Hi!
We got a machine with HP 11.23 upgraded with more memory and additional CPU. Although, the performance of all progs decreased over 15%. This is strange, as the server has more memory and CPU now. I was researching about any kernel parameters that must be updated, but I am not very experienced with kernel tuning. Can you imagine what could be wrong?
Thank you!

[Duncan Edmonstone · Accepted solution]

I can imagine plenty of things, but couldn't really comment on any of them with the level of data you have provided!

Questions:

What model of HP server is this? How many CPUs did it have before and after, how much memory before an after?

What is the application, how are you determining that it is performing 15% slower?

How did you reach the conclusion that more memory/CPUs is what you needed to speed up your application?

HTH

Duncan

[Kalin Evtimov]

Hi!
This is an rx4640 with HP-UX 11.23
It has 4 CPU's and 32 GB memory. It is running primarely an SAP-BW instances. But I also noticed that perl-data collectors, that I wrote became slower. We needed more memory, because the SAP was eating it all (16GB) and the system became unstable (process deactivating and swaping too much). Now it works fine, but slower. For a db-load we needed 13hrs before upgrade and for the same amount of data we need more than 16 hrs now.

[Steven E. Protter]

Shalom,

Shalom, remember I/O is the primary bottleneck on most systems these days. How fast disk writes are happening may have nothing to do with CPU and memory. It may have to do with the drive speed. Some Itanium systems have 10K SCSI instead of 15 K SCSI that was the standard in PA-RISC systems. This slows things down.

This doc will help you with tuning for performance.

http://www1.itrc.hp.com/service/cki/search.do?searchString=UPERFKBAN00000726&docType=Security&docType=Patch&docType=EngineerNotes&docType=BugReports&docType=Hardware&docType=ReferenceMaterials&docType=ThirdParty&searchCrit=allwords&search.x=28&admit=-682735245+1177317422000+28353475&category=c0&mode=id&search.y=8

SEP

[Duncan Edmonstone]

Yes, I would share SEP's initial asessment - if adding more CPUs slows things down that almost suggests more streams of work are being pushed at the disks...

If you've added memory and some of that is free you should belooking to increase the size of the Oracle SGA, and also keep a check on the size of your buffer cache. What size do you have dbc_min_pct and dbc_max_pct set to?

HTH

Duncan

[Kalin Evtimov]

kctune said:

dbc_min_pct 5 Default Immed
dbc_max_pct 5 5 Immed

Why should more I/O appear after CPU and memory came, the applications are the same.

Thank you.

[Rasheed Tamton]

Most probable cause might be the buffer cache as said above.

Please give the outputs of
# sysdef|grep dbc

(
It wiil give the output of
dbc_max_pct
dbc_min_pct
)

and

#swapinfo -tam

You might get more expert opinions based on that.

SEP, I am nto able to see the link. I am getting always a "System unavailable" message.

Regards.

[Kalin Evtimov]

Thank you,

The output is in the attached txt file.

SEP: I also cannot see the link, it seems that the document was renamed or deleted.

[Duncan Edmonstone]

Kalim,

It's not a great analogy, but think of your system as a water supply system.

Memory is the resevoir, CPU are the pumps, disk is the pipes out to consumers.

Now if the pipes were your bottleneck anyway, then adding more pumps and creating a bigger resevoir could actually make thinsg *worse*.

Like I said, not a good analogy! Do you have any disk IO metrics which might prove/disprove this theory? A simple sar -d 10 10 during the job thats taking lonegr might be a good starting point...

HTH

Duncan

[Kalin Evtimov]

This is the output (last lines),

13:21:01 c2t0d0 1.60 0.50 3 26 0.00 8.76
c2t1d0 1.00 0.50 2 23 0.00 5.58
c4t0d0 87.20 0.62 620 32503 0.09 4.04
13:21:11 c2t0d0 1.90 0.50 3 34 0.00 11.69
c2t1d0 1.00 0.50 2 31 0.00 7.67
c4t0d0 88.51 0.62 551 29445 0.08 4.44
13:21:21 c2t0d0 0.90 0.50 2 23 0.00 8.57
c2t1d0 0.60 0.50 1 21 0.00 6.03
c4t0d0 91.00 0.58 526 28868 0.05 4.60
13:21:31 c2t0d0 2.20 0.50 4 36 0.00 7.82
c2t1d0 1.10 0.50 3 31 0.00 4.70
c4t0d0 88.89 0.59 505 28306 0.06 4.48
13:21:41 c2t0d0 1.30 0.50 5 68 0.00 3.54
c2t1d0 0.60 0.50 1 16 0.00 5.56
c4t0d0 88.61 0.69 423 24461 0.20 5.25

Average c2t0d0 3.14 2.73 7 305 7.52 12.78
Average c2t1d0 1.73 3.17 5 63 7.39 10.76
Average c4t0d0 88.86 41.38 558 28633 34.68 4.56

This is when the SAP-Data-Load-application is running. I see the bottleneck here.

I have old data collected, but only for memory and load, not for diskIO, but I will watch the system for some days to see what is happening.

Thank you for your answers.