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

From: Steven Pratt (
Date: Tue Jun 10 2003 - 09:05:30 EST

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.


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