The ipr driver added some memory barriers in order to ensure
a PowerPC sync instruction was executed prior to sending a
command to the adapter to ensure the command block was
coherent with respect to the PCI bus's view of memory.
However, some time ago, the powerpc architecture writel
macros were changed to include the sync since most drivers
don't properly handle this. So remove these memory barriers
since they are not needed and result in executing twice
as many sync instructions, which has a significant performance
penalty.
Signed-off-by: Brian King <brking@xxxxxxxxxxxxxxxxxx>
---
drivers/scsi/ipr.c | 16 ++++------------
1 file changed, 4 insertions(+), 12 deletions(-)
diff -puN drivers/scsi/ipr.c~ipr_no_sync drivers/scsi/ipr.c
--- linux-2.6/drivers/scsi/ipr.c~ipr_no_sync 2012-03-10 07:32:35.000000000 -0600
+++ linux-2.6-bjking1/drivers/scsi/ipr.c 2012-03-10 07:32:35.000000000 -0600
@@ -850,8 +850,6 @@ static void ipr_do_req(struct ipr_cmnd *
ipr_trc_hook(ipr_cmd, IPR_TRACE_START, 0);
- mb();
-
ipr_send_command(ipr_cmd);
}
@@ -985,8 +983,6 @@ static void ipr_send_hcam(struct ipr_ioa
ipr_trc_hook(ipr_cmd, IPR_TRACE_START, IPR_IOA_RES_ADDR);
- mb();
-
ipr_send_command(ipr_cmd);
} else {
list_add_tail(&hostrcb->queue, &ioa_cfg->hostrcb_free_q);
@@ -5863,14 +5859,12 @@ static int ipr_queuecommand_lck(struct s
rc = ipr_build_ioadl(ioa_cfg, ipr_cmd);
}
- if (likely(rc == 0)) {
- mb();
- ipr_send_command(ipr_cmd);
- } else {
- list_move_tail(&ipr_cmd->queue, &ioa_cfg->free_q);
- return SCSI_MLQUEUE_HOST_BUSY;
+ if (unlikely(rc != 0)) {
+ list_move_tail(&ipr_cmd->queue, &ioa_cfg->free_q);
+ return SCSI_MLQUEUE_HOST_BUSY;
}
+ ipr_send_command(ipr_cmd);
return 0;
}
@@ -6248,8 +6242,6 @@ static unsigned int ipr_qc_issue(struct
return AC_ERR_INVALID;
}
- mb();
-
ipr_send_command(ipr_cmd);
return 0;
_
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