Re: how to demonstrate the effect of direct I/O ?

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On 02/04/2012 06:25 PM, Tomas Vondra wrote:
What should I do to see the effect of direct I/O?

Test something other than a mainstream Linux filesystem. The two times I've either measured an improvement myself for direct I/O were a) Veritas VxFS on Linux, which has some documented acceleration here and b) on Solaris. You won't find a compelling performance improvement listed at https://ext4.wiki.kernel.org/articles/c/l/a/Clarifying_Direct_IO%27s_Semantics_fd79.html and Linux has generally ignored direct I/O as something important to optimize for.

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Greg Smith   2ndQuadrant US    greg@xxxxxxxxxxxxxxx   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com


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