topic filecache_max running at high % in Operating System - HP-UX

filecache_max running at high %

Mauro Livi — Wed, 24 Jun 2015 22:20:07 GMT

Hi all,

We have a rx288 i4 running HP-UX 11.31 with 128GB Physical Memory. The server is being used primarily as a database server running Oracle 11g.

Recently while my DBA was doing a full refresh of a couple databases, I saw that the filecache_max kernel was running rather high (98%-99%....typically I see it somewhere between 50%-75%).

This is set to Auto tune, so it's not something that I've specifically set. If I understand correctly, this will then take up to 50% of the available memory, or approximately 60GB as its default value.

Doing a VMSTAT (sample output below) doesn't seem to show paging (though I swore I saw PO be something other than 0 at one point, however, that is consistently not the case now).

So I'm wondering if this shouls be taken off Auto tune and set to a lower value (say 30% of total memory?).

As always any input is greatly appreciated...and rewarded with kudos :)

Thanks

Mauro

    avm    free   re   at    pi   po    fr   de    sr     in     sy    cs
3599524 5824979    0    0     0    0     0    0     0   4197 32106 3323
CPU
    cpu          procs
us sy id    r     b     w
50 1 49    3     0     0
50 1 48
61 1 38
42 1 57

Disk Transfers
device    xfer/sec
   disk2        1
disk12      149
disk13      279
disk26      221
disk27      135
disk28      147
disk57       94
disk58       43
disk59       45
disk60       42
disk61       68
disk62       42
disk63       62
disk72       58
disk73       42
disk90        1
disk91        1
disk92        1
disk93        0
disk102        1
disk103        0
disk108        3
disk113        2
disk118       11
disk122        0
disk127        0
disk131        0

Re: filecache_max running at high %

SriniJay — Thu, 25 Jun 2015 20:45:38 GMT

On dedicated database servers, I would normally try to set memory free for the database. DBs like Oracle prefer to maintain its data all by itself including caching and doesn't always benefit from OS or file-system level caching (caching Oracle binaries is good, but caching huge database data files (dbf) doesn't do any good).

I've a huge database on rx8640 and runs great with filecache_max set to 20% and filecache_min set to 5%. On application side, I've set filecache_max set to 50% & min to 10%. Again, this all depends on how the servers are used. IF it is not a production server, go ahead and try tuning it down on the DB server.

Re: filecache_max running at high %

Mauro Livi — Thu, 25 Jun 2015 21:54:06 GMT

Thanks for the info SriniJay,

I'm currently trying different values for the filecache_max and see how the system behaves. Haven't touched filecache_min (yet).

One question. have you seen any difference in Page Outs by changing the filecache_max kernel? Just curious.

Thanks

Mauro

Re: filecache_max running at high %

SriniJay — Fri, 26 Jun 2015 13:40:30 GMT

Mauro,

No, I don't remember seeing page-outs probably because I tuned it down to smaller number immediately after building the system. I was shocked to see that all memory usage was by filecache when my servers were new & idle and so ended up reading this good article and tuning the server before installing the database.

Cheers,

Srini

Re: filecache_max running at high %

Mauro Livi — Fri, 26 Jun 2015 15:11:29 GMT

Thanks again.

When I set filecache_max to 20% I saw some page outs. When I left it at Auto (default) I did not (same process was run). So for the time being, we'll leave it at Auto.

I have the article so I'll read through it and see if I can pick up any hints.

Thanks

Mauro