On 01/25/2013 11:27 PM, Tejun Heo wrote: > Hey, Suresh. > > On Fri, Jan 25, 2013 at 06:49:34PM +0530, Suresh Jayaraman wrote: >> - Making cfq schedule the per cgroup sync/async queues according to I/O >> weights would mean that we'll need to use per cgroup cfqq's instead >> of per process? What will the impact on sync latencies if for example >> we have many sync only tasks in one cgroup and many async tasks in >> another? What if BLK_CGROUP is not configured, what would be the >> fallback behavior? > > So, we currently have synd cfqqs in cgroup cfqgs and shared cfqqs in > the root cfqg. The end result would be splitting shared cfqqs into > cgroup cfqgs. We may have to change how cfqgs are chosen depending on > whether it only has async IOs pending. Not sure. Ah, ok. Even if we have a way to check if in a particular cgroup all I/O is async or not, I have feeling that sync latencies might still get impacted for e.g. if we have a very few sync tasks plus many async tasks in one cgroup competing with all sync tasks in another group or some other combinations, no? Thanks -- Suresh Jayaraman -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
