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: Sam Bradshaw <sbradshaw@micron.com>
Add include of <linux/prefetch.h>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index 74abd49..295f3af 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -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 @@
/* 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 @@
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 @@
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 @@
* 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 @@
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 @@
{
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;