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. Cheers, Jeff [PATCH 1/4] cfq-iosched: Keep track of average think time for the sync-noidle workload. [PATCH 2/4] block: Implement a blk_yield function to voluntarily give up the I/O scheduler. [PATCH 3/4] jbd: yield the device queue when waiting for commits [PATCH 4/4] jbd2: yield the device queue when waiting for journal commits -- 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
