Vivek Goyal wrote:
o Currently a request queue has got fixed number of request descriptors for sync and async requests. Once the request descriptors are consumed, new processes are put to sleep and they effectively become serialized. Because sync and async queues are separate, async requests don't impact sync ones but if one is looking for fairness between async requests, that is not achievable if request queue descriptors become bottleneck. o Make request descriptor's per io group so that if there is lots of IO going on in one cgroup, it does not impact the IO of other group. o This patch implements the per cgroup request descriptors. request pool per queue is still common but every group will have its own wait list and its own count of request descriptors allocated to that group for sync and async queues. So effectively request_list becomes per io group property and not a global request queue feature. o Currently one can define q->nr_requests to limit request descriptors allocated for the queue. Now there is another tunable q->nr_group_requests which controls the requests descriptr limit per group. q->nr_requests supercedes q->nr_group_requests to make sure if there are lots of groups present, we don't end up allocating too many request descriptors on the queue. Signed-off-by: Nauman Rafique <nauman@xxxxxxxxxx> Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx> -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
