On Tue, Aug 22, 2017 at 08:51:32PM +0000, Bart Van Assche wrote: > On Sat, 2017-08-05 at 14:56 +0800, Ming Lei wrote: > > This patch introduces per-request_queue dispatch > > list for this purpose, and only when all requests > > in this list are dispatched out successfully, we > > can restart to dequeue request from sw/scheduler > > queue and dispath it to lld. > > Wasn't one of the design goals of blk-mq to avoid a per-request_queue list? Yes, but why does scsi device have per-request_queue depth? Anyway this single dispatch list won't hurt devices which doesn't have per-request_queue depth. For scsi device which has q->queue_depth, if one hctx is stuck, all hctxs are stuck actually, the single dispatch list just fits this kind of use case, doesn't it? -- Ming
