From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:35625) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QUd8O-0003xX-47 for qemu-devel@nongnu.org; Thu, 09 Jun 2011 07:10:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QUd8M-0004OX-QS for qemu-devel@nongnu.org; Thu, 09 Jun 2011 07:10:44 -0400 Received: from mail-px0-f174.google.com ([209.85.212.174]:44244) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QUd8M-0004OD-F2 for qemu-devel@nongnu.org; Thu, 09 Jun 2011 07:10:42 -0400 Received: by pxi15 with SMTP id 15so1027833pxi.33 for ; Thu, 09 Jun 2011 04:10:40 -0700 (PDT) Sender: Paolo Bonzini From: Paolo Bonzini Date: Thu, 9 Jun 2011 13:10:25 +0200 Message-Id: <1307617825-17149-3-git-send-email-pbonzini@redhat.com> In-Reply-To: <1307617825-17149-1-git-send-email-pbonzini@redhat.com> References: <1307617825-17149-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH 2/2] qemu-timer: change unix timer to dynticks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org A timer that wakes up every millisecond puts a lot of stress on the iothread. The large amount of IPIs causes very high context switch activity, making emulation slow and the UI unusable. This is by the way the same reason why the Windows timers were switched to dynticks. Signed-off-by: Paolo Bonzini Tested-by: Alexander Graf --- qemu-timer.c | 40 ++++++++++++++++++++++++++++------------ 1 files changed, 28 insertions(+), 12 deletions(-) diff --git a/qemu-timer.c b/qemu-timer.c index 4141b6e..5d78cc4 100644 --- a/qemu-timer.c +++ b/qemu-timer.c @@ -227,6 +227,7 @@ static void win32_rearm_timer(struct qemu_alarm_timer *t); static int unix_start_timer(struct qemu_alarm_timer *t); static void unix_stop_timer(struct qemu_alarm_timer *t); +static void unix_rearm_timer(struct qemu_alarm_timer *t); #ifdef __linux__ @@ -309,7 +310,7 @@ static struct qemu_alarm_timer alarm_timers[] = { /* ...otherwise try RTC */ {"rtc", rtc_start_timer, rtc_stop_timer, NULL}, #endif - {"unix", unix_start_timer, unix_stop_timer, NULL}, + {"unix", unix_start_timer, unix_stop_timer, unix_rearm_timer}, #else {"mmtimer", mm_start_timer, mm_stop_timer, NULL}, {"mmtimer2", mm_start_timer, mm_stop_timer, mm_rearm_timer}, @@ -1010,8 +1011,6 @@ static void dynticks_rearm_timer(struct qemu_alarm_timer *t) static int unix_start_timer(struct qemu_alarm_timer *t) { struct sigaction act; - struct itimerval itv; - int err; /* timer signal */ sigfillset(&act.sa_mask); @@ -1019,18 +1018,35 @@ static int unix_start_timer(struct qemu_alarm_timer *t) act.sa_handler = host_alarm_handler; sigaction(SIGALRM, &act, NULL); + return 0; +} - itv.it_interval.tv_sec = 0; - /* for i386 kernel 2.6 to get 1 ms */ - itv.it_interval.tv_usec = 999; - itv.it_value.tv_sec = 0; - itv.it_value.tv_usec = 10 * 1000; +static void unix_rearm_timer(struct qemu_alarm_timer *t) +{ + struct itimerval itv; + int64_t nearest_delta_ns = INT64_MAX; + int err; - err = setitimer(ITIMER_REAL, &itv, NULL); - if (err) - return -1; + assert(alarm_has_dynticks(t)); + if (!active_timers[QEMU_CLOCK_REALTIME] && + !active_timers[QEMU_CLOCK_VIRTUAL] && + !active_timers[QEMU_CLOCK_HOST]) + return; - return 0; + nearest_delta_ns = qemu_next_alarm_deadline(); + if (nearest_delta_ns < MIN_TIMER_REARM_NS) + nearest_delta_ns = MIN_TIMER_REARM_NS; + + itv.it_interval.tv_sec = 0; + itv.it_interval.tv_usec = 0; /* 0 for one-shot timer */ + itv.it_value.tv_sec = nearest_delta_ns / 1000000000; + itv.it_value.tv_usec = (nearest_delta_ns % 1000000000) / 1000; + err = setitimer(ITIMER_REAL, &itv, NULL); + if (err) { + perror("setitimer"); + fprintf(stderr, "Internal timer error: aborting\n"); + exit(1); + } } static void unix_stop_timer(struct qemu_alarm_timer *t) -- 1.7.4.4