On Fri, Nov 10, 2017 at 09:12:18AM -0700, Jens Axboe wrote: > Currently we are inconsistent in when we decide to run the queue. Using > blk_mq_run_hw_queues() we check if the hctx has pending IO before > running it, but we don't do that from the individual queue run function, > blk_mq_run_hw_queue(). This results in a lot of extra and pointless > queue runs, potentially, on flush requests and (much worse) on tag > starvation situations. This is observable just looking at the top > output, with lots of kworkers active. For the !async runs, it just adds > to the CPU overhead of blk-mq. > > Move the has-pending check into the run function instead of having > callers do it. > > Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Do we even still need the blk_mq_hctx_has_pending helper at all? Except for that this looks fine to me: Reviewed-by: Christoph Hellwig <hch@xxxxxx>
