Oracle FAQ | Your Portal to the Oracle Knowledge Grid |
Home -> Community -> Mailing Lists -> Oracle-L -> RE: CPU WAIT I/O statistic
Pablo - Another idea. Enter "man sar" at your command line. Here is the
paragraph from the Solaris manual. Hope this helps.
-u Report CPU utilization (the default):
%usr, %sys, %wio, %idle portion of time running in user mode, running in system mode, idle with some process waiting for block I/O, and otherwise idle.
In answer to your question, and I'm going beyond my knowledge and more guessing:
Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com
-----Original Message-----
Sent: Thursday, October 10, 2002 4:19 PM
To: Multiple recipients of list ORACLE-L
Dennis:
Thanks for answering, what do you mean by, or may be what do you think Gaja means by:
"He points out that the Solaris sar -q command has a
"%wio" column, a measure of processes that are
currently using the CPU, but are waiting for I/O
requests to be serviced and hence are not making
prudent use of the CPU"
How can the processes be using the CPIU if they are waiting for some I/O requests?
What I'm trying to say is that that can't consume CPU cicles if they are waiting (SLEEPING).
Why does sar shows that these CPU cicles are used in waiting for I/O? Who's using them?
TIA
Pablo - I posted the following paragraph yesterday:
3) I looked in Oracle Performance Tuning 101 to see
what Gaja has to say.
He points out that the Solaris sar -q command has a
"%wio" column, a measure
of processes that are currently using the CPU, but are
waiting for I/O
requests to be serviced and hence are not making
prudent use of the CPU. He
further says that %sys and %wio should be less than
10-15% and if it is
consistently higher you need to get to the bottom of
it, and usually it is a
application causing the problem. No details on how to
get to the bottom.
Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com
-----Original Message-----
Sent: Thursday, October 10, 2002 3:16 PM
To: Multiple recipients of list ORACLE-L
Hi list
Can anyone explain me what exactly does the WAIT I/O column of the sar -u output mean?
Does it represent the % of CPU used by the kernel processes to perform I/O?
As far as I know the waiting processes do no wait actively when they ask for an I/O. right? The OS uses the SLEEP and WAKEUP primitives.
So, Which process is using this CPU? (The WAIT I/O%)
Or does this WAIT I/O have to be taken as if the CPU were idle?
Please shed some light on this.
Thanks
-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: =?iso-8859-1?q?Pablo=20Rodriguez?= INET: p_rodri99_at_yahoo.es Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: DENNIS WILLIAMS INET: DWILLIAMS_at_LIFETOUCH.COM Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Thu Oct 10 2002 - 16:58:50 CDT