Hello,
Platform is Oracle 11.2.0.3 64-bit on Oracle Linux 6.2 64-bit. Storage is on iSCSI.
After enabling async i/o on the database level (disk_asynch_io=TRUE and filesystemio_options=SETALL), we notice a significantly lower performance (up to 25% slower).
aio-max-nr is set to 1048576.
Any idea what could be wrong? There are no network issues, CPU load seems ok...
This is the result of a level 8 10046 trace:
Async i/o disabled:
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
Disk file operations I/O 4 0.00 0.00
db file sequential read 166147 2.21 84.01
db file scattered read 2406 1.74 7.05
undo segment extension 2 0.01 0.01
log file switch completion 2 0.02 0.05
log buffer space 4 2.86 2.92
latch free 1 0.00 0.00
db file parallel read 2 0.15 0.19
direct path write temp 577 0.53 2.46
latch: shared pool 11 0.00 0.00
direct path read temp 577 0.01 0.54
latch: object queue header operation 1 0.00 0.00
1 session in tracefile.
11 user SQL statements in trace file.
6 internal SQL statements in trace file.
17 SQL statements in trace file.
13 unique SQL statements in trace file.
5583431 lines in trace file.
409 elapsed seconds in trace file.
Async i/o enabled:
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
Disk file operations I/O 3 0.00 0.00
db file sequential read 143264 0.78 242.64
latch: cache buffers lru chain 2 0.00 0.00
latch: object queue header operation 2 0.00 0.00
log file switch completion 3 0.06 0.15
db file scattered read 2333 0.07 4.93
asynch descriptor resize 1 0.00 0.00
log buffer space 3 0.13 0.25
direct path read temp 97 0.00 0.32
reliable message 67 0.00 0.03
latch: cache buffers chains 1 0.00 0.00
1 session in tracefile.
11 user SQL statements in trace file.
6 internal SQL statements in trace file.
17 SQL statements in trace file.
13 unique SQL statements in trace file.
5560145 lines in trace file.
716 elapsed seconds in trace file.
Regards,
Matthias Hoys
matthiashoys.wordpress.com
Edited by: mhoys on May 16, 2012 11:50 AM