On Mon, Mar 02, 2020 at 02:15:41PM +0100, Christoph Hellwig wrote: > On Mon, Mar 02, 2020 at 10:58:55AM +0000, John Garry wrote: > > On 28/02/2020 09:33, Ming Lei wrote: > >> scsi host template struct is quite big, and the following three > >> fields are needed in SCSI IO path: > >> > >> - queuecommand > >> - commit_rqs > >> - cmd_size > > > > Would it have been nearly as good to reorganise Scsi host template > > structure to ensure that these are adjacent? > > > > I say nearly, as it avoids the shost->hostt read. > > That would be worth trying. Replicating function pointers out of > read-only data structures generally isn't a very good idea. > OK, I will try to re-organize host template and see if it can reach same performance, but it still introduces one extra fetch in IO path. BTW, we replicate function pointer in blk-mq too, such as q->mq_ops. Thanks, Ming
