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mtip32xx: minor performance enhancements

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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 <sbradshaw@micron.com>

Add include of <linux/prefetch.h>

Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Sam Bradshaw 2014-06-06 13:28:48 -06:00 committed by Jens Axboe
parent f6be4fb4bc
commit f45c40a92d
2 changed files with 13 additions and 10 deletions
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15
drivers/block/mtip32xx/mtip32xx.c
View File

@ -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;

8
drivers/block/mtip32xx/mtip32xx.h
View File

@ -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