Regarding Deferred swap reservation failure pid: 22748 error

[Kavita Poonia]

Hello Techies,

I am getting below error for one of my HP-UX server.

Jun 19 13:07:42 psgtwq1 vmunix: Deferred swap reservation failure pid: 22748

I am pasting here swapinfo output. Please let me know what needs to be done to remove this error. Do I have to increase the value for Kernel Parameters "maxdsiz" and "mxadsize_64bit" which is 1G & 2G presently.

# swapinfo -tam
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 8192 3 8189 0% 0 - 1 /dev/vg00/lvol2
reserve - 8184 -8184
memory 24443 5093 19350 21%
total 32635 13280 19355 41% - 0 -

Thanks & regards,
Kavita

[Steven E. Protter · Accepted solution]

Shalom,

This means a process asked for swap and did not get it.

I do recommend increasing the two parameters you mention.

Your system does not seem to be under a lot of memory stress.

You have 24 GB of RAM and 8 GB of swap, and that could be a problem. Swap needs as a minimum to be half of RAM.

I think if you run vmstat you will find your system is not paging.

SEP

[Kavita Poonia]

Hello Steven,

Yes, you are right....system is not paging.

# vmstat 5 5
procs memory page faults cpu
r b w avm free re at pi po fr de sr in sy cs us sy id
5 0 0 2586355 2573428 37 7 98 0 0 0 0 2315 54204 1296 4 2 94
5 0 0 2586355 2573349 43 4 14 0 0 0 0 4964 290360 31117 24 15 61
8 2 0 2596453 2573349 16 0 129 0 0 0 0 5073 326725 29535 25 13 62
8 2 0 2596453 2571267 74 24 396 0 0 0 0 4833 441104 26744 25 13 62
3 3 0 2646826 2571600 28 7 128 0 0 0 0 3867 261251 22526 28 11 61
#


Thanks & regards,
Kavita

[Steven E. Protter]

Shalom,

Take care of those kernel parameters and increase swap to 12 GB.

You may never page, but you need that much to handle reservation requests.

http://docs.hp.com/en/B2355-90950/ch06s03.html

http://docs.hp.com/en/B2355-90672/ch06s04.html

http://docs.hp.com/en/B2355-90672/ch06s07.html

Those docs will tell you how to add a secondary swap. Take your choice.

Adding swap requires a boot.

SEP

[James R. Ferguson]

Hi:

> SEP: Adding swap requires a boot

No, it does not. _Removing_ swap (unless you have 'swapoff' and 11.31) requires are rboot; not adding secondary swap.

...JRF...

[Kavita Poonia]

Thanks Steven. I will go with increasing those Kernel Parameters & device swap too.

Thanks James....yes adding secondary swap does not require reboot until n unless, we do not need to increase KPs maxswapchunks & swchunk to add extra device swap.

[James R. Ferguson]

Hi (again) Kavita:

> yes adding secondary swap does not require reboot until n unless, we do not need to increase KPs maxswapchunks & swchunk to add extra device swap.

Well, 'maxswapchunks' ceased to exist in 11.23 and tuning 'swchunks' is rarely necessary, At 11.31, up to 4,096 TB of swap space is possible, by default.

Regards!

...JRF...

[Steven E. Protter]

A thought came to mind.

Since no reboot is required to add swap. I actually like one single primary swap area of 50% of RAM. Extending that swap area might require a reboot. Which is what I may have been thinking.

Add an additional swap area (secondary) device swap of 4 GB.

You can make the priority different than primary swap so it will not be used unless the system is stressed.

SEP

[James R. Ferguson]

Hi (again):

> SEP: I actually like one single primary swap area of 50% of RAM. Extending that swap area might require a reboot.

Since primary swap has to be allocated with contiguous extents, extending primary swap is tedious if not extremely difficult. Re-igniting is one option.

There is no difference in the way the system views primary or secondary device swap other than its up to you to activate secondary swap during startup.

Regards!

...JRF...

[Kavita Poonia]

Hello All,

I tried increasing those two Kernel Parameters and swap space too of 4 GB but still the same error is coming when we try to run lots of 32 bit programs together.

One more thing I want to ask here is that do all 32 bit programs have to share same 4GB address space. So, even though system has lot of memory, memory for 32 bit programs is only 4GB.

There is lots of confusion about a single 32 bit program needing more than 4GB memory vs all 32 bit programs combined needing more than 4GB memory. Maxdsiz parameter etc help a single program to have higher memory, but problem here is that all 32 programs combined are restricted to 4GB memory. If I shutdown some programs and then run java, then error does not come.

I hope you all got my point here.

Thanks & regards,
Kavita

[Steven E. Protter]

Shalom,

For 32 bit programs the memory limit is usually 2 GB, but memory windows can be used to get to 4 GB.

Perhaps that is old info, because I saw a java heap thread a few days ago that indicated the hard limit was being reached at 4 GB, though java may be using memory windows behind the scenes.

Better to trust the doc than my pea brain molecules.

Memory tuning guide:
http://docs.hp.com/en/1219/tuningwp.html

32 and 64 bit interoperability:
http://www.docs.hp.com/en/5966-9844/ch02s08.html
# may not be relevant


Memory limits for 32 bit programs on 64 bit systems:
http://docs.hp.com/en/5966-9844/ch03s04.html

I think the last document is best because I liked it so much, I stopped looking.

SEP

[Dennis Handly]

>I tried increasing those two Kernel Parameters and swap space too of 4 GB but still the same error is coming when we try to run lots of 32 bit programs together.

Then you need lots more swapspace. Is it always the psgtwq1 process?

>do all 32 bit programs have to share same 4GB address space?

It depends on how the program is linked. By default they have 1 Gb for the executable, 1 Gb private and can share 2 Gb. Depending on the architecture, MPAS or memory windows, they can have 4 Gb private.

>If I shutdown some programs and then run java, then error does not come.

Then you have a swapspace limitation.

>SEP: I saw a java heap thread a few days ago that indicated the hard limit was being reached at 4 GB

Probably this thread:
http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1349336