Direct io - oracle but very high page cache rate
Tolga Evren
tolgae at paro.com.tr
Mon Sep 12 13:56:58 UTC 2005
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
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