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.
--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) {
--
1.7.2.5
root@tifa:/usr/src/lio-core-2.6.git#
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