On 14/03/2016 12:21, Denis V. Lunev wrote:
> 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.
Have you encountered a place that was calling them so hard that it
caused performance problem? If so, the logging should probably be
replaced by a tracepoint.
Paolo
> Signed-off-by: Denis V. Lunev <d...@openvz.org>
> CC: Stefan Hajnoczi <stefa...@redhat.com>
> CC: Paolo Bonzini <pbonz...@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)
>
