This patch adds the following: 1) Compiler hinting in the fast path. 2) A prefetch of port->flags to eliminate moderate cpu stalling later in mtip_hw_submit_io(). 3) Eliminate a redundant rq_data_dir(). 4) Reorder members of driver_data to eliminate false cacheline sharing between irq_workers_active and unal_qdepth.
With some workload and topology configurations, I'm seeing ~1.5% throughput improvement in small block random read benchmarks as well as improved latency std. dev. Signed-off-by: Sam Bradshaw <[email protected]> --- diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c index 74abd49..fcbac54 100644 --- a/drivers/block/mtip32xx/mtip32xx.c +++ b/drivers/block/mtip32xx/mtip32xx.c @@ -2380,6 +2380,8 @@ static void mtip_hw_submit_io(struct driver_data *dd, struct request *rq, /* Map the scatter list for DMA access */ nents = dma_map_sg(&dd->pdev->dev, command->sg, nents, dma_dir); + prefetch(&port->flags); + command->scatter_ents = nents; /* @@ -2392,7 +2394,7 @@ static void mtip_hw_submit_io(struct driver_data *dd, struct request *rq, fis = command->command; fis->type = 0x27; fis->opts = 1 << 7; - if (rq_data_dir(rq) == READ) + if (dma_dir == DMA_FROM_DEVICE) fis->command = ATA_CMD_FPDMA_READ; else fis->command = ATA_CMD_FPDMA_WRITE; @@ -2412,7 +2414,7 @@ static void mtip_hw_submit_io(struct driver_data *dd, struct request *rq, fis->res3 = 0; fill_command_sg(dd, command, nents); - if (command->unaligned) + if (unlikely(command->unaligned)) fis->device |= 1 << 7; /* Populate the command header */ @@ -2433,7 +2435,7 @@ static void mtip_hw_submit_io(struct driver_data *dd, struct request *rq, * To prevent this command from being issued * if an internal command is in progress or error handling is active. */ - if (port->flags & MTIP_PF_PAUSE_IO) { + if (unlikely(port->flags & MTIP_PF_PAUSE_IO)) { set_bit(rq->tag, port->cmds_to_issue); set_bit(MTIP_PF_ISSUE_CMDS_BIT, &port->flags); return; @@ -3754,7 +3756,7 @@ static bool mtip_check_unal_depth(struct blk_mq_hw_ctx *hctx, struct driver_data *dd = hctx->queue->queuedata; struct mtip_cmd *cmd = blk_mq_rq_to_pdu(rq); - if (!dd->unal_qdepth || rq_data_dir(rq) == READ) + if (rq_data_dir(rq) == READ || !dd->unal_qdepth) return false; /* @@ -3776,11 +3778,11 @@ static int mtip_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *rq) { int ret; - if (mtip_check_unal_depth(hctx, rq)) + if (unlikely(mtip_check_unal_depth(hctx, rq))) return BLK_MQ_RQ_QUEUE_BUSY; ret = mtip_submit_request(hctx, rq); - if (!ret) + if (likely(!ret)) return BLK_MQ_RQ_QUEUE_OK; rq->errors = ret; diff --git a/drivers/block/mtip32xx/mtip32xx.h b/drivers/block/mtip32xx/mtip32xx.h index 4b9b554..ba1b31e 100644 --- a/drivers/block/mtip32xx/mtip32xx.h +++ b/drivers/block/mtip32xx/mtip32xx.h @@ -493,19 +493,19 @@ struct driver_data { struct workqueue_struct *isr_workq; - struct mtip_work work[MTIP_MAX_SLOT_GROUPS]; - atomic_t irq_workers_active; + struct mtip_work work[MTIP_MAX_SLOT_GROUPS]; + int isr_binding; struct block_device *bdev; - int unal_qdepth; /* qdepth of unaligned IO queue */ - struct list_head online_list; /* linkage for online list */ struct list_head remove_list; /* linkage for removing list */ + + int unal_qdepth; /* qdepth of unaligned IO queue */ }; #endif -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
