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.
-- Greg Smith 2ndQuadrant US greg@xxxxxxxxxxxxxxx Baltimore, MD PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
