On 5/22/18 10:44 AM, Jens Axboe wrote: > > On 5/22/18 10:25 AM, Bart Van Assche wrote: >> Recently the blk-mq timeout handling code was reworked. See also Tejun >> Heo, "[PATCHSET v4] blk-mq: reimplement timeout handling", 08 Jan 2018 >> (https://www.mail-archive.com/linux-block@xxxxxxxxxxxxxxx/msg16985.html). >> This patch reworks the blk-mq timeout handling code again. The timeout >> handling code is simplified by introducing a state machine per request. >> This change avoids that the blk-mq timeout handling code ignores >> completions that occur after blk_mq_check_expired() has been called and >> before blk_mq_rq_timed_out() has been called. > > I'll take a look at this again, getting rid of cmpxchg64 makes me > much more comfortable. FWIW, a quick pass on runtime testing works fine. As expected, it's more efficient than what's currently in the kernel, testing with both null_blk (1 and nr_cpus worth of queues), and nvme as well. A huge win is that we shrink the request size from 360 bytes to 312, and I did a small followup patch that brings that to 304. That's a 15% reduction, massive. -- Jens Axboe
