On Wed, Jan 18, 2017 at 04:27:24PM +0200, Sagi Grimberg wrote: > > >So what you say is you saw a consomed == 1 [1] most of the time? > > > >[1] from http://git.infradead.org/nvme.git/commitdiff/eed5a9d925c59e43980047059fde29e3aa0b7836 > > Exactly. By processing 1 completion per interrupt it makes perfect sense > why this performs poorly, it's not worth paying the soft-irq schedule > for only a single completion. > > What I'm curious is how consistent is this with different devices (wish > I had some...) Hannes just spotted this: static int nvme_queue_rq(struct blk_mq_hw_ctx *hctx, const struct blk_mq_queue_data *bd) { [...] __nvme_submit_cmd(nvmeq, &cmnd); nvme_process_cq(nvmeq); spin_unlock_irq(&nvmeq->q_lock); return BLK_MQ_RQ_QUEUE_OK; out_cleanup_iod: nvme_free_iod(dev, req); out_free_cmd: nvme_cleanup_cmd(req); return ret; } So we're draining the CQ on submit. This of cause makes polling for completions in the IRQ handler rather pointless as we already did in the submission path. -- Johannes Thumshirn Storage jthumshirn@xxxxxxx +49 911 74053 689 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg) Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850 -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
