From: Judith Lebzelter <judith@osdl.org>
To: linux-aio@kvack.org
Cc: suparna@in.ibm.com, linux-osdl@osdl.org
Subject: [linux-osdl] OSDL aio-stress result on buffered reads for recent AIO patch set
Date: Thu, 22 Jul 2004 15:12:33 -0700

Hello;

I have run aio-stress on the OSDL conduit, which includes the recent
aio patch set from Suparna Bhattacharya on linux-2.6.7.  I have found
inconsistant throughput for buffered sequential and random reads.

On 2-CPU/1G/ext2 run with 4 X 1G files:
             2.6.7^     aio-patch*  aio-patch** aio-patch***
                           run 1       run 2      run 3
Seq Read    24.36 MB/s  45.83 MB/s   28.27 MB/s   1.25 MB/s
Ran Read     7.14 MB/s   1.33 MB/s    4.08 MB/s  13.71 MB/s

Raw data:
^http://khack.osdl.org/stp/295153/results/runlog.buffer.txt
^^http://khack.osdl.org/stp/295109/results/runlog.buffer.txt
*http://khack.osdl.org/stp/295135/results/runlog.buffer.txt
**http://khack.osdl.org/stp/295132/results/runlog.buffer.txt
***http://khack.osdl.org/stp/295110/results/runlog.buffer.txt


For the patched kernel run 295110, the Sequential read throughput
was very inconsistant across files.  For run 295135 the Random
reads were inconsistant across files.  In general runs do not
seem reproducible.

However, for the linux-2.6.7 the throughput is generally consistant
across files for a single run, and reproducible across seperate
runs.

I see similar inconsistancy on the 1CPU host and the 4CPU host:
    http://khack.osdl.org/stp/295107/results/runlog.buffer.txt
    http://khack.osdl.org/stp/295113/results/runlog.buffer.txt


I am seeing a message on the console 'AIO readahead congestion' over and
over again while the test is running for at least some runs.

Are my options realistic?  Or any other suggestions??  I plan to run
a few more tests on other filesystem types and with oprofile.

Regards;

Judith Lebzelter
OSDL