On Mon, Apr 17, 2017 at 10:30:46AM -0700, Omar Sandoval wrote: > On Mon, Apr 17, 2017 at 12:03:53AM +0800, Ming Lei wrote: > > On Sat, Apr 15, 2017 at 08:38:21PM +0800, Ming Lei wrote: > > > The 1st patch enhances BLK_MQ_F_NO_SCHED so that we can't change/ > > > show available io schedulers on devices which don't support io > > > scheduler. > > > > > > The 2nd patch passes BLK_MQ_F_NO_SCHED for avoiding one regression > > > on mtip32xx, which is introduced by blk-mq io scheduler. > > > > > > The last two patches introduce BLK_MQ_F_SCHED_USE_HW_TAG so that > > > we can allow to use hardware tag for scheduler, then mq-deadline > > > can work well on mtip32xx. Even though other devices with enough > > > hardware tag space can benefit from this feature too. > > > > > > The 1st two patches aims on v4.11, and the last two are for > > > v4.12. > > > > Please ignore this patchset, and I will post another serial for > > mtip32xx fix. > > > > thanks, > > Ming > > Regardless of the mtip32xx fix, I actually wanted to skip the scheduler > tags when possible just for performance reasons. I don't think that > should be a device-specific setting. We can let the I/O scheduler decide > how many tags it wants, and if the device has at least that many tags, > just use the hardware tags directly. I'll probably look at doing that > for 4.13, we'll see if it actually makes a performance difference. Yes, I thought about that too, the following policy may be applied at default: - if queue depth is not less than q->nr_requests and - the tag space isn't shared We still can keep the flag of BLK_MQ_F_SCHED_USE_HW_TAG so that drivers can decide if they want to do that, since I guess it may help some shared tag cases too. Now the mtip32xx fix has been sent out already, I will post this patchset of using hw tag for scheduler out soon for review. Thanks, Ming
