filecache_max running at high %

[Mauro Livi]

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

[SriniJay]

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.

[Mauro Livi]

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

[SriniJay]

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

[Mauro Livi]

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