The value of OS' file cache

[rustam_2]

Hi all,
Recently my server had Panic Shutdown. I called to support center and then they required to send crash file. In few days they determined that i have some problem with OS, such as:
...

3. A big value of memory uses for file system cache. Because i use Oracle DB there and DB uses own cache value.

Tunables
========
filecache_max = 47.6%
filecache_min = 4.8%
fs_meta_max = 46.6%
fs_meta_min = 1.0%

He recommended to turn off or decrease the file system cache value.

So what do you think, should i turn off or decrease this value? And do you know any documents where is the description of this operation. I mean where is the clear description of doing this trip.

Regards,
Rustam

[Michal Kapalka (mikap)]

hi,

you could read this docu :

"HP-UX Performance Cookbook"

http://h21007.www2.hp.com/portal/download/files/unprot/devresource/Docs/TechPapers/UXPerfCookBook.pdf

mikap

[James R. Ferguson]

Hi Rustam:

Have a look at the manpages for 'filecache_max(5)' as a guide.

Regards!

...JRF...

[rustam_2]

Thanks, mikap and JRF.
I read both material and decided to change this value. First i wanted to check the memory value. I found out strange value on my server. I have 2 servers prod and test, i attached screen of top command.
Prod has:
Memory: 5195184K (1353332K) real, 7307632K (1888260K) virtual, 395860K free Page
e# 1/22
So
-RAM is 8Gb - used 5.2 Gb of them.
-Virtual memory is 1Gb and used 700Mb

Test has:
Memory: 12330140K (3462780K) real, 21361628K (7866040K) virtual, 117708K free Pa
age# 1/32

How many GB are for TEST server is used?

Regards,
Rustam.

[Dennis Handly]

Yes, your file cache numbers are too big for database servers.
Please provide the "swapinfo -tam" values for each machine.

[rustam_2]

Hi Dennis,
I attached the result of swapinfo tam od prod and test. Test uses 90% of swap memory and prod just 42%. Therefore he suggested to turn off or decrease cache info for FileSystem. What do you think?

Regards,
Rustam.

[Dennis Handly]

>I attached the result of swapinfo -tam of prod and test.

(It would be more helpful to attach a text file, since I can't grep or diff pixels.)

>Test uses 90% of swap memory and prod just 42%. Therefore he suggested to turn off or decrease cache info for FileSystem. What do you think?

Yes, it makes a lot of sense. Lots more memory is used for caching? in the second case.

[rustam_2]

> (It would be more helpful to attach a text file, since I can't grep or diff pixels.)

For prod
# swapinfo -tam
Mb Mb Mb PCT
TYPE AVAIL USED FREE USED
dev 8192 0 8192 0%
reserve - 7078 -7078
memory 15555 2909 12646 19%
total 23747 9987 13760 42%

For test
# swapinfo -tam
Mb Mb Mb PCT
TYPE AVAIL USED FREE USED
dev 8192 5152 3040 63%
reserve - 3040 -3040
memory 15555 13328 2227 86%
total 23747 21520 2227 91%

>>Yes, it makes a lot of sense. Lots more memory is used for caching? in the second case.

So i have to turn off file cache value?

Regards,
Rustam.

[Dennis Handly]

>So I have to turn off file cache value?

No, just reduce it to a smaller value. Check the value of filecache_max on prod and set test to that value. But if it is 50%, you could just set it to 6% or so.

[rustam_2]

Hi Dennis,
I checked the value of filecache_max on both server and there are default values - 8155217920. In test is used percentage is 98% and in prod is 16%. How can i check the value of filecache_max in %?

Regards,
Rustam