Direct io - oracle but very high page cache rate

[Tolga Evren]

Hi ,

 

My system is redhat linux on ia64 with ocfs. The db server is the main
application . Oracle uses direct-io by default. Considering oracle
bypasses the page cache since it uses direct io why does the system has
4687296 kB allocated as cache? 

 

 

[oracle at tanidw1 proc]$ cat meminfo

        total:    used:    free:  shared: buffers:  cached:

Mem:  8490827776 8407597056 83230720        0 309854208 5101617152

Swap: 25165725696 568295424 24597430272

MemTotal:      8291824 kB

MemFree:         81280 kB

MemShared:           0 kB

Buffers:        302592 kB

Cached:        4687296 kB

SwapCached:     294752 kB

Active:        2665648 kB

Inact_dirty:   3367248 kB

Inact_clean:    121328 kB

Inact_target:  1230832 kB

HighTotal:           0 kB

HighFree:            0 kB

LowTotal:      8291824 kB

LowFree:         81280 kB

SwapTotal:    24575904 kB

SwapFree:     24020928 kB

Committed_AS: 569088960 kB

HugePages_Total:     0

HugePages_Free:      0

Hugepagesize:    262144 kB

 

 

Sar -B 

 

[oracle at tanidw1 proc]$ sar -B 1 10

Linux 2.4.18-e.37smp (tanidw1)  09/12/2005

 

03:58:18 PM  pgpgin/s pgpgout/s  activepg  inadtypg  inaclnpg  inatarpg

03:58:19 PM  16524.00  22039.00    170661    206385      7164     76842

03:58:20 PM  23579.00   3936.00    170667    206444      7164     76855

03:58:21 PM  15180.00     91.00    170657    206511      7164     76866

03:58:22 PM  14522.00     14.00    170657    206579      7164     76880

03:58:23 PM  12252.00    127.00    170657    206640      7164     76892

03:58:24 PM   9882.00   5319.00    170661    206695      7164     76904

03:58:25 PM  10268.00     15.00    170661    206751      7163     76915

03:58:26 PM  18988.00     79.00    170661    206812      7163     76927

 

 

How can i see that whether these pagings occur in order to cache more
file data or another?

 

 

Kind Regards,

Tolga Evren