[Qemu-devel] [PATCH 5/9] log: improve performance of qemu_log and qemu_log_mask if disabled

["Denis V. Lunev" <den@openvz.org>]

The patch is intended to avoid to perform any operation including
calculation of log function arguments when the log is not enabled due to
various reasons.

Functions qemu_log and qemu_log_mask are replaced with variadic macros.

Format checking performed by compiler will not suffer by this patch. It
will be done inside in fprintf arguments checking.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Paolo Bonzini <pbonzini@redhat.com>
---
 include/qemu/log.h | 15 ++++++++++++---
 util/log.c         | 21 ---------------------
 2 files changed, 12 insertions(+), 24 deletions(-)

diff --git a/include/qemu/log.h b/include/qemu/log.h
index 2c2c220..a05c7dc 100644
--- a/include/qemu/log.h
+++ b/include/qemu/log.h
@@ -54,7 +54,12 @@ static inline bool qemu_loglevel_mask(int mask)
 
 /* main logging function
  */
-void GCC_FMT_ATTR(1, 2) qemu_log(const char *fmt, ...);
+#define qemu_log(...)                          \
+    do {                                       \
+        if (qemu_log_enabled()) {              \
+           fprintf(qemu_logfile, __VA_ARGS__); \
+        }                                      \
+    } while (0)
 
 /* vfprintf-like logging function
  */
@@ -68,8 +73,12 @@ qemu_log_vprintf(const char *fmt, va_list va)
 
 /* log only if a bit is set on the current loglevel mask
  */
-void GCC_FMT_ATTR(2, 3) qemu_log_mask(int mask, const char *fmt, ...);
-
+#define qemu_log_mask(mask, ...)                                \
+    do {                                                        \
+        if ((qemu_loglevel & (mask)) && qemu_log_enabled()) {   \
+           fprintf(qemu_logfile, __VA_ARGS__);                  \
+        }                                                       \
+    } while (0)
 
 /* Maintenance: */
 
diff --git a/util/log.c b/util/log.c
index df672cc..65d46e2 100644
--- a/util/log.c
+++ b/util/log.c
@@ -27,27 +27,6 @@ FILE *qemu_logfile;
 int qemu_loglevel;
 static int log_append = 0;
 
-void qemu_log(const char *fmt, ...)
-{
-    va_list ap;
-
-    va_start(ap, fmt);
-    if (qemu_logfile) {
-        vfprintf(qemu_logfile, fmt, ap);
-    }
-    va_end(ap);
-}
-
-void qemu_log_mask(int mask, const char *fmt, ...)
-{
-    va_list ap;
-
-    va_start(ap, fmt);
-    if ((qemu_loglevel & mask) && qemu_logfile) {
-        vfprintf(qemu_logfile, fmt, ap);
-    }
-    va_end(ap);
-}
 
 /* enable or disable low levels log */
 void do_qemu_set_log(int log_flags, bool use_own_buffers)
-- 
2.5.0