On Tue, May 27, 2014 at 03:56:00PM -0400, Mikulas Patocka wrote: > > > On Tue, 27 May 2014, Jens Axboe wrote: > > > On 2014-05-27 10:26, Mikulas Patocka 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. > > > > Except such a thing already exists, there are unplug callback chains. All I'm > > asking is that you look into how feasible it would be to use something like > > that, instead of reinventing the wheel. > > > > -- > > Jens Axboe > > Do you mean moving current->bio_list to struct blk_plug and calling > blk_start_plug/blk_finish_plug around generic_make_request? > > It would be possible on a condition that we can redirect all bios to a > workqueue (i.e. eliminate bio_kmalloc and always use bio_alloc_bioset). > > What are performance implications of this - does it make sense to have > blk_start_plug/blk_finish_plug around every call to generic_make_request? > - that means that all i/o requests will be added to a plug and then > unplugged. We've already got blk_start_plug() calls around IO submission at higher points in the stack. (I actually have seen it show up in profiles though, it probably would be worth inlining and slimming down a bit). -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
