On Wed, Feb 25 2015 at 6:57pm -0500, Keith Busch <keith.busch@xxxxxxxxx> wrote: > On Wed, 25 Feb 2015, Mike Snitzer wrote: > >On Wed, Feb 25 2015 at 1:17pm -0500, > >Busch, Keith <keith.busch@xxxxxxxxx> wrote: > >>Our first bottleneck appears to be the device mapper's single lock > >>request queue. > > > >Obviously if we switched dm-multipath over to blk-mq we'd eliminate > >that. I'll see how things go and will share any changes I come up > >with. > > Yes, I'm also looking at blk-mq. It appears conversion helps a lot. Oh, so you've already started a conversion of request-based DM? > I'm not sure though how many tags or h/w contexts to allocate to ensure > there's enough but not too many. You can't use the underlying device's > blk-tagset count (assuming you could even get to it) since those are > potentially shared among many block devices. I'm very new to the blk-mq model so I have some learning to do before I'll be much help. But there really won't be a one size fits all amount for those resources will there? A multipath device can have _a lot_ of underlying paths. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
