Tunning the UBC

[Dermot Paikkos <dermot@xxxxxxxxxxxxxxxx>]

Hi Managers,

SYS: DS10, Tru64 5.1 advfs 1280MB RAM

I am trying to fine tune the memory usage on our system and have hit 
something that doesn't seem correct. The problem original stemmed 
from the memory error when using ImageMagick.

I have recently increased the RAM on our server so was surprised to 
find that the performance of IM was not boosted. vmstat (-P) shows a 
lot of pages allocated to the unified buffer cache:

free pages = 8296
active pages = 7675
inactive pages = 7974
wired pages = 15303
ubc pages = 119873
==================
       Total = 159121


I read that I can check the efficiency of the UBC by doing dbx -k  
/vmunix and checking the hits and misses with a pd 
ufs_getapage_stats. But when I try this I am getting a zero for all 

struct {
    read_looks = 0
    read_hits = 0
    read_miss = 0
    alloc_error = 0
    alloc_in_cache = 0

The ufs seems to indicate that this would only work with a ufs file 
system and we are using advfs. Should I be using a different command 
in dbx? Does the ubc pages above seems high? What is the best way to 
reduce this if I should?

Thanx.
Dp.


~~
Dermot Paikkos * dermot@xxxxxxxxxxxxxxxx
Network Administrator @ Science Photo Library
Phone: 0207 432 1100 * Fax: 0207 286 8668