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

From: Nick Piggin (
Date: Mon Jun 09 2003 - 19:13:30 EST

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

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