Async IO on Linux

  • From: "Hostetter, Jay M" <JHostetter@xxxxxxxxxxxxxxxxxxxx>
  • To: <Oracle-L@xxxxxxxxxxxxx>
  • Date: Thu, 21 Sep 2006 15:40:14 -0400

I'm testing 10gR2 on a new Linux box.  I decided to fiddle with enabling
async IO.  To test the async IO, I imported a table and I also ran
several queries . I ran these tests one at a time (e.g. the queries and
imports were not running simultaneously).  I see NO performance
difference for my import or queries with async IO enabled.  I expected
to see some performance difference (meaing change in elapsed time).
Does async IO only help when you have multiple sessions performing IO
Redhat Linux 2.6.9-5.ELsmp
I enabled async IO as follows:
$cd $ORACLE_HOME/rdbms/lib
$ln -s /usr/lib/ skgaio.o
$make PL_ORALIBS=-laio -f async_on
filesystemio_options =asynch 
Stats change when I check slabinfo, so it appears as though async io is
cat /proc/slabinfo | grep -e kio -e name
As a side note, enabling the deadline scheduler DID reduce the time it
took for an import (elevator=deadline in /etc/grub.conf).  The import
went from 26 minutes to 11 minutes.
Thank you,

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