On Wed, Apr 14 2010, Jeff Moyer wrote: > Hi, > > The previous two postings can be found here: > http://lkml.org/lkml/2010/4/1/344 > and here: > http://lkml.org/lkml/2010/4/7/325 > > The basic problem is that, when running iozone on smallish files (up to > 8MB in size) and including fsync in the timings, deadline outperforms > CFQ by a factor of about 5 for 64KB files, and by about 10% for 8MB > files. From examining the blktrace data, it appears that iozone will > issue an fsync() call, and subsequently wait until its CFQ timeslice > has expired before the journal thread can run to actually commit data to > disk. > > The approach taken to solve this problem is to implement a blk_yield call, > which tells the I/O scheduler not to idle on this process' queue. The call > is made from the jbd[2] log_wait_commit function. > > This patch set addresses previous concerns that the sync-noidle workload > would be starved by keeping track of the average think time for that > workload and using that to decide whether or not to yield the queue. > > My testing showed nothing but improvements for mixed workloads, though I > wouldn't call the testing exhaustive. I'd still very much like feedback > on the approach from jbd/jbd2 developers. Finally, I will continue to do > performance analysis of the patches. This is starting to look better. Can you share what tests you did? I tried reproducing with fs_mark last time and could not. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
