From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56760) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1afTWF-0002OF-6O for qemu-devel@nongnu.org; Mon, 14 Mar 2016 10:30:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1afTWB-0000MX-5m for qemu-devel@nongnu.org; Mon, 14 Mar 2016 10:30:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33950) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1afTWA-0000MO-Py for qemu-devel@nongnu.org; Mon, 14 Mar 2016 10:30:47 -0400 References: <1457954501-26528-1-git-send-email-den@openvz.org> <1457954501-26528-6-git-send-email-den@openvz.org> From: Paolo Bonzini Message-ID: <56E6CB13.3020406@redhat.com> Date: Mon, 14 Mar 2016 15:30:43 +0100 MIME-Version: 1.0 In-Reply-To: <1457954501-26528-6-git-send-email-den@openvz.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 5/9] log: improve performance of qemu_log and qemu_log_mask if disabled List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Denis V. Lunev" Cc: qemu-devel@nongnu.org, Stefan Hajnoczi 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 > CC: Stefan Hajnoczi > CC: Paolo Bonzini > --- > 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) >