swap utilization is high

[Sridhar Bhaskarla]

Hi,

Yes. You will have to. Yours is a good example for depending too much on pseudo_swap. You will not be able to bring up more processes as there is no (little) swap space left for the system to reserve for the new processes.

You are confusing 'swap space needed to hold paged out memory' with 'swap space needed to bring up more processes'.

-Sri

[Hanry Zhou]

Sri,

Thanks for the message, and I understand what you are saying here.

Now, purely from the system performance point of view, withought considering if any additional processes could be lanuched or not, do I have to increase the size of device swap?

In another words, in this case, with only size of 1gb device swap, would that effect my system performance/speed? remember the swap util on device swap is only 0%.

Thanks,

[Sridhar Bhaskarla]

Hi Hanry,

From the performance perspective, the answer is 'no'. The answer given earlier to increase your device swap was to your initial question that the SWAP was reaching 90% sometimes.

See my last but two messages and post the outputs of those commands.

-Sri

[Ted Buis]

I think I was so busy explaining swap that I neglected the main issue which is slow response time. There may not be a connection in your case between the two. I would use glance to see what other system bottlenecks might be possible due to resource depletion, like file locks, number of processes, etc. I'm assuming that since you have Glance you can easily see that you aren't CPU or I/O bound.

The cause for "slowness" that I have seen over and over again, has to do with networking. Either a mismatch between the speed or duplex setting of the LAN card versus the switch setting, or slowness of name resolution (DNS service is slow). Due some nslookups and some pings to see how these perform. Check for network errors.

While I still wouldn't be comfortable with 1GB of swap on a 6GB machine, it may not be the source of your "slowness".

[Hanry Zhou]

Sri,

You answered my Q.

Now, I'd like to go back to one of your previous posting which is very interesting, and I'd like to quote them here:
"I would ask as very basic question. When you said there were intermittent slow downs, are they related to the response to the commands or they really slowing down the system so that processing is delayed?"

Now, my question is, what is the difference between these two situations, one is slowness to respond my commands, and another is that system processes is delayed? What would be the different reasons causing these two diffrent situation?

Ted, I agree with you, and I should increase the device swap. The reason I asked that the question was to verify if my understanding is correct.

[Sridhar Bhaskarla]

Hanry,

Look at Bill's response on the slow response. I couldn't put it any better than him. I also gave you an example with an NFS mount which can considerably slow down 'ls', 'bdf' etc.,

If you can post the outputs of the commands I gave, one may be able to get some idea on your system.

-Sri

[Ted Buis]

If you have NFS mounts, I would recommend the presentation and/or book by David Olker on NFS Performance. Number one tip that I got out of it is to use 11i if NFS peformance is important.

[Sumesh Shivdas_1]

The command ITO uses to determine the SWAP utilization is

swapinfo -dftr

It does not account for the psedo swap.