Re: [Qemu-devel] [PATCH v4 04/11] qemu-log: Avoid function call for disabled qemu_log_mask logging

[Aurelien Jarno <aurelien@aurel32.net>]

On 2015-08-03 10:14, Alex Bennée wrote:
> From: Peter Maydell <peter.maydell@linaro.org>
> 
> Make qemu_log_mask() a macro which only calls the function to
> do the actual work if the logging is enabled. This avoids making
> a function call in possible fast paths where logging is disabled.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> Reviewed-by: Andreas Färber <afaerber@suse.de>
> 
> ---
> v4
>   - fix s-o-b tags, add r-b tag
> ---
>  include/qemu/log.h | 13 ++++++++++---
>  qemu-log.c         | 11 -----------
>  2 files changed, 10 insertions(+), 14 deletions(-)
> 
> diff --git a/include/qemu/log.h b/include/qemu/log.h
> index f880e66..b80f8f5 100644
> --- a/include/qemu/log.h
> +++ b/include/qemu/log.h
> @@ -65,10 +65,17 @@ qemu_log_vprintf(const char *fmt, va_list va)
>      }
>  }
>  
> -/* log only if a bit is set on the current loglevel mask
> +/* log only if a bit is set on the current loglevel mask:
> + * @mask: bit to check in the mask
> + * @fmt: printf-style format string
> + * @args: optional arguments for format string
>   */
> -void GCC_FMT_ATTR(2, 3) qemu_log_mask(int mask, const char *fmt, ...);
> -
> +#define qemu_log_mask(MASK, FMT, ...)                   \
> +    do {                                                \
> +        if (unlikely(qemu_loglevel_mask(MASK))) {       \
> +            qemu_log(FMT, ## __VA_ARGS__);              \
> +        }                                               \
> +    } while (0)
>  
>  /* Special cases: */
>  
> diff --git a/qemu-log.c b/qemu-log.c
> index be8405e..7036076 100644
> --- a/qemu-log.c
> +++ b/qemu-log.c
> @@ -36,17 +36,6 @@ void qemu_log(const char *fmt, ...)
>      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)
>  {

Good idea.

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>


-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net