To minimize the overhead of debug printouts during non-debug runs,
the check for "is_debug" is moved from log_debug() function
to dprintf() macro.
Now log_debug is called only if "is_debug" is set.
This spares a function call, parameter passing and the costs of
complex arguments expanding and evaluation.
To minimize the potential cost of log_debug() even more,
the check for is_debug is put under unlikely() statement.
Signed-off-by: Alexander Nezhinsky <alexandern@xxxxxxxxxxxx>
---
usr/log.c | 5 +----
usr/log.h | 6 +++++-
usr/tgtd.h | 1 +
3 files changed, 7 insertions(+), 5 deletions(-)
diff --git a/usr/log.c b/usr/log.c
index 056314a..66f3e14 100644
--- a/usr/log.c
+++ b/usr/log.c
@@ -43,7 +43,7 @@
static struct logarea *la;
static char *log_name;
-static int is_debug;
+int is_debug = 0;
static pid_t pid;
static int logarea_init (int size)
@@ -297,9 +297,6 @@ void log_error(const char *fmt, ...)
void log_debug(const char *fmt, ...)
{
- if (!is_debug)
- return;
-
va_list ap;
va_start(ap, fmt);
dolog(LOG_DEBUG, fmt, ap);
diff --git a/usr/log.h b/usr/log.h
index b84f6d6..426237e 100644
--- a/usr/log.h
+++ b/usr/log.h
@@ -28,6 +28,9 @@
#include <sys/sem.h>
+#define likely(x) __builtin_expect(!!(x), 1)
+#define unlikely(x) __builtin_expect(!!(x), 0)
+
union semun {
int val;
struct semid_ds *buf;
@@ -76,7 +79,8 @@ do { \
#define dprintf(fmt, args...) \
do { \
- log_debug("%s(%d) " fmt, __FUNCTION__, __LINE__, ##args); \
+ if (unlikely(is_debug)) \
+ log_debug("%s(%d) " fmt, __FUNCTION__, __LINE__, ##args); \
} while (0)
#endif /* LOG_H */
diff --git a/usr/tgtd.h b/usr/tgtd.h
index 3323a9b..cc2c468 100644
--- a/usr/tgtd.h
+++ b/usr/tgtd.h
@@ -207,6 +207,7 @@ static inline int kreq_init(void) \
#endif
extern int system_active;
+extern int is_debug;
extern int kspace_send_tsk_mgmt_res(struct mgmt_req *mreq);
extern int kspace_send_cmd_res(uint64_t nid, int result, struct scsi_cmd *);
--
1.6.5
--
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