Re: what is "kfk: async disk IO"?
- From: Dion Cho <ukja.dion@xxxxxxxxx>
- To: martin.a.berger@xxxxxxxxx
- Date: Fri, 10 Dec 2010 15:18:49 +0900
As Freek has pointed it out, "kfk" is related to asynch I/O. Exactly
speaking, kfk layer is activated by disk_asynch_io parameter being true.
If the problem persists, strace on the process would give additional info
about the asynchronous I/O system call.
And you can get parameter info from V$EVENT_NAME as following.
TPACK@ukja1120> exec print_table('select * from v$event_name where name like
''kfk''');
EVENT# : 377
EVENT_ID : 1568594048
NAME : kfk: async disk IO
PARAMETER1 : count
PARAMETER2 : intr
PARAMETER3 : timeout
WAIT_CLASS_ID : 4108307767
WAIT_CLASS# : 9
WAIT_CLASS : System I/O
================================
Dion Cho - Oracle Performance Storyteller
http://dioncho.wordpress.com (english)
http://ukja.tistory.com (korean)
http://sites.google.com/site/otpack (tpack)
================================
On Tue, Dec 7, 2010 at 7:50 PM, Martin Berger <martin.a.berger@xxxxxxxxx>wrote:
> Freek,
>
> thank you for your clarification.
> Currently I'm not so much on the performance tuning side. It's more a kind
> of troubleshooting, where I still does not know how to catch the situation.
> Some minutes after my observation the instance hang as all sessions where
> used - not even sys could logon. (yes, prelim worked, but that's not the
> issue here).
> No, my colleague did not create a systemdump or hanganalyze or similar....
>
> Even it's only a 'test' system we had to restart the instance. Without any
> big investigation.
> Now I'm searching what this "kfk: async disk IO" is. Maybe someone has some
> infos about P1, P2, P3. I will try to grab some informations out of ASH or
> other resources, based on this.
>
> Martin
>
> Am 07.12.2010 um 10:42 schrieb D'Hooge Freek:
>
> > Martin,
> >
> > The "kfk: async disk IO" seems to be linked to the io_submit system call.
> > You could check your number of async io processes.
> >
> > But don't look at the number of occurrences to determine how "heavy" an
> event is, look at the time spend. There is no relation between number of
> occurrences and time spend.
> >
> >
> > Regards,
> >
> >
> > Freek D'Hooge
> > Uptime
> > Oracle Database Administrator
> > email: freek.dhooge@xxxxxxxxx
> > tel +32(0)3 451 23 82
> > http://www.uptime.be
> > disclaimer: www.uptime.be/disclaimer
> > --
> > From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:
> oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Martin Berger
> > Sent: dinsdag 7 december 2010 9:50
> > To: Oracle-L Freelists
> > Subject: what is "kfk: async disk IO"?
> >
> > Hi,
> >
> > can anyone please hint me to some information about
> > kfk: async disk IO ?
> >
> > A little query on v$sessions gave me
> > USERNAME EVENT
> COUNT(*)
> > ------------------------------
> -------------------------------------------------- ----------
> > APPS ges message buffer allocation
> 98
> > APPS CSS operation: action
> 2
> > APPS Streams AQ: waiting for messages in the
> queue 9
> > SYS SQL*Net message to client
> 1
> > APPS SQL*Net message from client
> 147
> > APPS kfk: async disk IO
> 1646
> >
> > as kfk: async disk IO is the bigest contributor, I'd like to investigate
> a little bit.
> >
> > for the records: 11.2.0.1 - 2 node RAC - RedHat 5.4 Linux 64-bit. (yes,
> it's EBS - but don't ask me the exact pach level, please - I assume
> 11.5.10???)
> >
> > thnx
> > Martin
>
> --
> //www.freelists.org/webpage/oracle-l
>
>
>
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