Hi, This is V2 of the patch series to use same scheduling logic for cfq queues as we use for cfq groups. This applies on top of cfq cleanup changes I posted here.
http://lkml.indiana.edu/hypermail/linux/kernel/1210.0/01966.html Bot the patch series have been generated on top of 3.6 in linus tree. Why to change scheduling algorithm ================================== Currently we use two scheduling algorithms at two different layers. vdisktime based algorithm for groups and round robin for cfq queues. Now we are planning to do more development in cfqq so that it can handle group hierarchies. And I think before we do that we first need to change the code so that both queues and groups are treated same way when it comes to scheduling. Otherwise the whole thing is a mess. This patch series does not merge the queue and group scheduling code. It just tries to make these similar enough so that merging of code becomes easier in future patches. What's the functionality impact =============================== Total disk share (time slices) allocated to each prio queue should become predictable and every queue gets its fair share of disk in proportion to its prio/weight. This works only if we idle on the cfq queue (rotational disk and low end SSD). For SSD with queue depth more than certain requests, we don't idle on queues and there will be no priority differentiation between various queues. In did my testing on a SATA rotational disk and lauched 8 processes with prio 0-7, all doing sequential reads. Here are the results. 0 1 3 4 4 5 6 7 vanilla(MB/s) 14.0 9.8 7.6 6.4 5.0 3.4 2.2 1.6 patched(MB/s) 27.5 15.2 8.0 4.8 3.1 2.1 1.3 .8 Notice that service differentiation of IO between different prio level has significantly on this disk. I guess that's a good thing. Roughly each prio level should get 1.6 times more time slice as compared to previous prio level. This is easily modifiable in code if people find this kind of service differentiation is too much. Also note that total throughput of disk has increased. I think it has happened because low prio queue gets scheduled less number of times hence resulting in less number of seeks. Thanks Vivek Vivek Goyal (8): cfq-iosched: Make cfq_scale_slice() usable for both queues and groups cfq-iosched: make new_cfqq variable bool cfq-iosced: Do the round robin selection of workload type cfq-iosched: Put new queue at the end of servie tree always cfq-iosched: Remove residual slice logic cfq-iosched: put cooperating queue at the front of service tree cfq-iosched: Use same scheduling algorithm for groups and queues cfq-iosched: Wait for queue to get busy even if this is not last queue in group block/blk-cgroup.h | 2 +- block/cfq-iosched.c | 313 ++++++++++++++++++++++++++++++--------------------- 2 files changed, 187 insertions(+), 128 deletions(-) -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
