On Tue, May 27, 2014 at 01:33:06PM -0400, Mike Snitzer wrote: > On Tue, May 27 2014 at 12:26pm -0400, > Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > On Tue, 27 May 2014, Jens Axboe wrote: > > > > > On 2014-05-27 09:23, Mikulas Patocka wrote: > > > > > > > The patch adds bio list flushing to the scheduler just besides plug > > > > flushsing. > > > > > > ... which is exactly why I'm commenting. It'd be great to avoid yet one more > > > scheduler hook for this sort of thing. > > > > > > -- > > > Jens Axboe > > > > One could create something like schedule notifier chain, but I'm not sure > > if it is worth the complexity because of just two users. If more users > > come in the future, it could be generalized. > > It could be that Jens is suggesting updating blk_needs_flush_plug() and > blk_schedule_flush_plug() to be bio_list aware too (rather than train > sched_submit_work() from this new bio_list)? > > Somewhat awkward, but _could_ be made to work. No... I started on this ages and ages ago, but the patches were nowhere near ready to go out. What I'd do is rework the existing blk_plug to work in terms of bios, not requests. This is a fair amount of work, and then make_request_fn() needs to be able to take multiple bios at a time, but IIRC there were other simplifications that fell out of this and this also means bio based drivers can take advantage of plugging/batching. Once this is done, you just... replace the bio list in generic_make_request() with a plug. Boom, done. (oh, and to avoid blowing the stack the scheduler/plug callback or whatever needs to check the current stack usage and punt off to a per request_queue workqueue, but that's easy enough). -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
