Red Hat Bugzilla – Bug 588219
25% performance regression of concurrent O_DIRECT writes. [rhel-5.5.z]
Last modified: 2015-05-04 21:19:56 EDT
This bug has been copied from bug #574285 and has been proposed
to be backported to 5.5 z-stream (EUS).
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
When two or more writes which used the O_DIRECT file access interface were run simultaneously on two separate partitions on the same disk, performance of both writes were reduced. This could have caused a write slowdown of approximately 25% when running two simultaneous "dd oflag=direct" commands on two different partitions. This regression has been fixed in this update so that O_DIRECT write performance does not incur a performance penalty.
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.