paging space usage plummets

[bi]

We have two paging spaces: hd6 and paging00. hd6 got up to 100% used. paging00 got up to 73% used. hd6 was one physical partition short of our standard of 2 GB. (The system has 2GB real memory and we allocate double the amount of memory for paging space. hd6 should have had 2 GB and paging had 2 GB.)

I added one 32 MB partition to hd6 and usage went from 100% to 25%

Why did it plummet so much and so fast (in a matter of seconds)?

 

[RodKnowlton]

Here's my theory:

When you extended the paging space, the virtual memory manager had to rebalance things (or something like that) based on the new configuration. In order to facilitate this, it flushed most file (perm) pages out of real memory and paged in a bunch of the program (comp) pages from the paging space you were extending.

If I'm right, and you make no other adjustments, the paging use on hd6 will rise back to its previoius level after roughly 3/4 the amount of time it takes it to get there when starting from a fresh boot.

I'll be interested to know if that happens. Keep us posted.


- Rod

IBM Certified Advanced Technical Expert pSeries and AIX 5L
CompTIA Linux+
CompTIA Security+

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[khalidaaa]

Nice theory Rod

I think it is quite right but we will wait for bi reply.

Regards,
Khalid

 

[bi]

Paging space on the secondary paging space has remained steady at 75%. primary has been going up 1 percentage point a day, which is what secondary was doing when primary was 100% utilized.

 

[RodKnowlton]

Sounds like there's a memory leak somewhere, or processes are finishing but not exiting (which is a memory leak, just at a higher level).

What's vmstat look like under a typical load? Does "ps aux | wc -l" increase from day to day?

Also, if you want to keep paging balanced between all spaces during normal operations, you should make hd6 larger than the other spaces. Since hd6 is available earlier than the others, it actually ends up with paging activity before the round robin algorithm kicks in on most systems. Take a look immediately after boot to see how much bigger.

- Rod


IBM Certified Advanced Technical Expert pSeries and AIX 5L
CompTIA Linux+
CompTIA Security+

Wish you could view posts with a fixed font? Got Firefox & Greasemonkey? Give yourself the option.