Re: 2.5.70-mm2 causes performance drop of random read O_DIRECT

[Steven Pratt <slpratt@austin.ibm.com>]

Nick Piggin wrote:

> Steven Pratt wrote:
>
>> Starting in 2.5.70-mm2 and continuing in the mm tree, there is a 
>> significant degrade in random read for block devices using 
>> O_DIRECT.   The drop occurs for all block sizes and ranges from 
>> 30%-40.  CPU usage is also lower although it may already be so low as 
>> to be irrelavent.
>
> Hi Steven, this is quite likely to be an io scheduler problem.
> Is your test program rawread v2.1.5?

This test was actually using 2.1.4, but the only difference in the 2.1.5 
version is a fix for the test label array for the aio versions of the 
test.  No functional change, just fixed the outputed test description.

> What is the command line you are using to invoke the program? 

rawread -t6 -p8 -m1 -d2 -s4096 -n65536 -l1 -z -x

Which you can find if you follow either results link and look in the 
benchmark directory where all raw benchmark out put is stored.

Steve