On Thu, 1 Dec 2011, Nicholas A. Bellinger wrote:
On Thu, 2011-12-01 at 09:12 +0100, Sebastian Andrzej Siewior wrote:
On 11/30/2011 11:03 PM, Nicholas A. Bellinger wrote:
diff --git a/drivers/scsi/qla2xxx/qla_dbg.c b/drivers/scsi/qla2xxx/qla_dbg.c
index 07372de..cc32ec8 100644
--- a/drivers/scsi/qla2xxx/qla_dbg.c
+++ b/drivers/scsi/qla2xxx/qla_dbg.c
@@ -1676,11 +1676,11 @@ ql_dbg(uint32_t level, scsi_qla_host_t *vha, int32_t id, char *msg, ...) {
uint32_t len;
struct pci_dev *pdev = NULL;
- memset(pbuf, 0, QL_DBG_BUF_LEN);
-
va_start(ap, msg);
if ((level& ql2xextended_error_logging) == level) {
+ memset(pbuf, 0, QL_DBG_BUF_LEN);
+
512bytes on the stack is brave.
...
Anyway, why do you memset the whole
buffer? As far the string processing is concerned, setting the first
byte to zero is enough.
After converting qla_target.c in a few hundred locations to use
qla_dbg() my wrists are still hurting, so you can imagine I'm not real
eager to look into this code. ;)
Anyways, memset of the whole buffer is overkill. Since sprintf() is
being used for qla_dbg.c cases, even the 1 byte memset is unnecessary.
I do want to note that there is a patch posted already that removes the
memset as well:
http://marc.info/?l=linux-scsi&m=132163664809856&w=2.
--nab
From 25541e7f09b87de0000b11506d49695183aab4f1 Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Date: Wed, 30 Nov 2011 13:57:02 -0800
Subject: [PATCH] qla2xxx: Remove memset debug buffer with sprintf usage
During recent perf testing with qla_target.c logic, dl_dbg() appeared
as one of the top CPU consumers (~5% CPU) with small block random I/O
even when no debug levels have been enabled.
This patch drops the explict memset() in four qla_dbc.c functions
as we expect sprintf() to add the trailing NULL when debug is enabled.
Cc: Andrew Vasquez <andrew.vasquez@xxxxxxxxxx>
Cc: Giridhar Malavali <giridhar.malavali@xxxxxxxxxx>
Cc: Roland Dreier <roland@xxxxxxxxxxxxxxx>
Cc: Joern Engel <joern@xxxxxxxxx>
Cc: James Bottomley <JBottomley@xxxxxxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
drivers/scsi/qla2xxx/qla_dbg.c | 8 --------
1 files changed, 0 insertions(+), 8 deletions(-)
diff --git a/drivers/scsi/qla2xxx/qla_dbg.c b/drivers/scsi/qla2xxx/qla_dbg.c
index 07372de..ef31819 100644
--- a/drivers/scsi/qla2xxx/qla_dbg.c
+++ b/drivers/scsi/qla2xxx/qla_dbg.c
@@ -1676,8 +1676,6 @@ ql_dbg(uint32_t level, scsi_qla_host_t *vha, int32_t id, char *msg, ...) {
uint32_t len;
struct pci_dev *pdev = NULL;
- memset(pbuf, 0, QL_DBG_BUF_LEN);
-
va_start(ap, msg);
if ((level & ql2xextended_error_logging) == level) {
@@ -1724,8 +1722,6 @@ ql_dbg_pci(uint32_t level, struct pci_dev *pdev, int32_t id, char *msg, ...) {
if (pdev == NULL)
return;
- memset(pbuf, 0, QL_DBG_BUF_LEN);
-
va_start(ap, msg);
if ((level & ql2xextended_error_logging) == level) {
@@ -1763,8 +1759,6 @@ ql_log(uint32_t level, scsi_qla_host_t *vha, int32_t id, char *msg, ...) {
uint32_t len;
struct pci_dev *pdev = NULL;
- memset(pbuf, 0, QL_DBG_BUF_LEN);
-
va_start(ap, msg);
if (level <= ql_errlev) {
@@ -1823,8 +1817,6 @@ ql_log_pci(uint32_t level, struct pci_dev *pdev, int32_t id, char *msg, ...) {
if (pdev == NULL)
return;
- memset(pbuf, 0, QL_DBG_BUF_LEN);
-
va_start(ap, msg);
if (level <= ql_errlev) {
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