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Description of problem: IO controller has IO throttling policy. That throttling policy takes request queue lock for every bio even if there are no throttling rules in the group. Request queue lock is already heavily contended. This patch series avoids taking that lock when there are no rules in the group. This is a common scenario for majority of customers where there are no rules in root group while IO is happening. Avoid taking request queue lock for such cases. This series also makes some of the stats per cpu so that we avoid taking blkg->stats_lock. Version-Release number of selected component (if applicable): How reproducible: Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info:
This request was evaluated by Red Hat Product Management for inclusion in a Red Hat Enterprise Linux maintenance release. Product Management has requested further review of this request by Red Hat Engineering, for potential inclusion in a Red Hat Enterprise Linux Update release for currently deployed products. This request is not yet committed for inclusion in an Update release.
Patch(es) available on kernel-2.6.32-160.el6
Confirmed blkio stats described in the patches are present and blkio controller is functional using both ltp tests as well as throttling I/O in a guest system on a RHEL 6.2 host.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. http://rhn.redhat.com/errata/RHSA-2011-1530.html