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Method R and CPU Time
- From: "MacGregor, Ian A." <ian@xxxxxxxxxxxxxxxxx>
- To: "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 1 Jul 2004 13:42:00 -0700
I'm having a hard time determining how much time is actually spent on CPU,
Consider the following
Runtime TRACE_ID EVENT WAITS
WAIT_SECS ELAPSED_SECS CPU_SECS
25-JUN-2004 12:05 nlco_ora_7279 db file sequential read 96
.27 14.29 13.07
25-JUN-2004 12:05 db file scattered read 378
7.14 14.29 13.07
25-JUN-2004 12:05 SQL*Net message from client 475
1.34 14.29 13.07
*************************** -----
-----
sum 949
8.75
The CPU_SECS + WAIT_SECS should equal elapsed secs at least approximately. I
know there is some double counting between the file i/o waits and the CPU's
but 13.07 + 8.75 = 21.82 and 21.82/14.29 * 100 = anout 153%. That's a lot more
than the incidental double-counting error Cary speaks of in his book.
This particular machine has 4 CPU's and when looking at CPU usage at the system
level one needs to take that into account. But what about for individual
statements that are not parallelized; i.e., running against one and only one
CPU, does one need to divide the CPU results by four on a four CPU machine.
Ian MacGregor
Stanford Linear Accelerator Center
iam@xxxxxxxxxxxxxxxxx
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