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Commit f45c40a9 authored by Sam Bradshaw's avatar Sam Bradshaw Committed by Jens Axboe
Browse files

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.

Signed-off-by: default avatarSam Bradshaw <sbradshaw@micron.com>

Add include of <linux/prefetch.h>

Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent f6be4fb4

drivers/block/mtip32xx/mtip32xx.c

+9 −6
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ 
#include <../drivers/ata/ahci.h>

#include <linux/export.h>

#include <linux/debugfs.h>

#include <linux/prefetch.h>

#include "mtip32xx.h"



#define HW_CMD_SLOT_SZ		(MTIP_MAX_COMMAND_SLOTS * 32)
@@ -2380,6 +2381,8 @@ 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 +2395,7 @@ 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 +2415,7 @@ 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 +2436,7 @@ 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 +3757,7 @@ 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 +3779,11 @@ 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
Original line number Diff line number Diff line
@@ -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