I don't think this is going to help __multipath_map() without some configuration changes. Now that we're running on already merged requests instead of bios, the m->repeat_count is almost always set to 1, so we call the path_selector every time, which means that we'll always need the write lock. Bumping up the number of IOs we send before calling the path selector again will give this patch a change to do some good here.To do that you need to set: rr_min_io_rq <something_bigger_than_one> in the defaults section of /etc/multipath.conf and then reload the multipathd service. The patch should hopefully help in multipath_busy() regardless of the the rr_min_io_rq setting.This patch, while generic, is meant to help the blk-mq case. A blk-mq request_queue doesn't have an elevator so the requests will not have seen merging. But yes, implied in the patch is the requirement to increase m->repeat_count via multipathd's rr_min_io_rq (I'll backfill a proper header once it is tested).
I'll test it once I get some spare time (hopefully soon...) -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
