mtip32xx: minor performance enhancements
PATCH 1/1 mtip32xx: minor performance enhancements
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.
---
drivers/block/mtip32xx/mtip32xx.c +8 -6
@@ -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;
drivers/block/mtip32xx/mtip32xx.h +4 -4
@@ -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
Jens Axboe
maintainerQuoted 9 lines · Sam Bradshaw
This patch adds the following:
1) Compiler hinting in the fast path.
2) A prefetch ofport->flagsto eliminate moderate cpu stalling later inmtip_hw_submit_io().
3) Eliminate a redundantrq_data_dir().
4) Reorder members ofdriver_datato eliminate false cacheline sharing betweenirq_workers_activeandunal_qdepth.
Quoted 3 lines
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.
Seems I got a small bump in peak perf as well. In any case, it's innocuous, so should do no harm to apply.
Signature · 1 line
Jens Axboe