On Thu, Jul 18, 2013 at 3:47 PM, Akemi Yagi <amyagi at gmail.com> wrote: > On Thu, Jul 18, 2013 at 2:07 PM, Karanbir Singh <mail-lists at karan.org> wrote: >> Which then has me thinking - what is the actual problem we are trying to >> solve here ? and how can I ratify that ? > > All details are given in CentOS bug #6548 (links therein) but here's > is a short summary of the events that were seen in the kernel > development [list]. > > Someone reported "bad performance with SSD since kernel version > 2.6.32". After bisection, he found the following commit to be the > likely culprit: > > commit fb1e75389bd06fd5987e9cda1b4e0305c782f854 > Author: Jens Axboe <jens.axboe at xxxxxxxxxx> > Date: Thu Jul 30 08:18:24 2009 +0200 > (This was added to kernel 2.6.32) > > Long story short, this commit was reverted in kernel 2.6.33: > > commit 79da0644a8e0838522828f106e4049639eea6baf > Author: Jens Axboe <jens.axboe at oracle.com> > Date: Tue Feb 23 08:40:43 2010 +0100 (snip) Just wanted to update the status of the issue. (1) Current centosplus kernel 2.6.32-358.18.1.el6.centos.plus has the patch from the second commit quoted above that is supposed to rectify the issue. (2) I've filed a bug report upstream: https://bugzilla.redhat.com/show_bug.cgi?id=1003678 (It's marked private) >From the way it looks, the patch will be pulled in to the RHEL kernel but no specific version is given. Akemi