From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45422) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1chDw7-00079I-MD for qemu-devel@nongnu.org; Fri, 24 Feb 2017 06:21:21 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1chDw6-0000BX-Ch for qemu-devel@nongnu.org; Fri, 24 Feb 2017 06:21:19 -0500 Received: from mail-wm0-x230.google.com ([2a00:1450:400c:c09::230]:38772) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1chDw6-0000AO-6V for qemu-devel@nongnu.org; Fri, 24 Feb 2017 06:21:18 -0500 Received: by mail-wm0-x230.google.com with SMTP id r141so12081147wmg.1 for ; Fri, 24 Feb 2017 03:21:18 -0800 (PST) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= Date: Fri, 24 Feb 2017 11:20:51 +0000 Message-Id: <20170224112109.3147-7-alex.bennee@linaro.org> In-Reply-To: <20170224112109.3147-1-alex.bennee@linaro.org> References: <20170224112109.3147-1-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [Qemu-devel] [PULL 06/24] tcg: add kick timer for single-threaded vCPU emulation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: peter.maydell@linaro.org Cc: qemu-devel@nongnu.org, =?UTF-8?q?Alex=20Benn=C3=A9e?= , Paolo Bonzini , Peter Crosthwaite , Richard Henderson Currently we rely on the side effect of the main loop grabbing the iothread_mutex to give any long running basic block chains a kick to ensure the next vCPU is scheduled. As this code is being re-factored and rationalised we now do it explicitly here. Signed-off-by: Alex Bennée Reviewed-by: Richard Henderson Reviewed-by: Pranith Kumar --- cpus.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) diff --git a/cpus.c b/cpus.c index c94b3307e5..9fe56c9a76 100644 --- a/cpus.c +++ b/cpus.c @@ -768,6 +768,53 @@ void configure_icount(QemuOpts *opts, Error **errp) } /***********************************************************/ +/* TCG vCPU kick timer + * + * The kick timer is responsible for moving single threaded vCPU + * emulation on to the next vCPU. If more than one vCPU is running a + * timer event with force a cpu->exit so the next vCPU can get + * scheduled. + * + * The timer is removed if all vCPUs are idle and restarted again once + * idleness is complete. + */ + +static QEMUTimer *tcg_kick_vcpu_timer; + +static void qemu_cpu_kick_no_halt(void); + +#define TCG_KICK_PERIOD (NANOSECONDS_PER_SECOND / 10) + +static inline int64_t qemu_tcg_next_kick(void) +{ + return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD; +} + +static void kick_tcg_thread(void *opaque) +{ + timer_mod(tcg_kick_vcpu_timer, qemu_tcg_next_kick()); + qemu_cpu_kick_no_halt(); +} + +static void start_tcg_kick_timer(void) +{ + if (!tcg_kick_vcpu_timer && CPU_NEXT(first_cpu)) { + tcg_kick_vcpu_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, + kick_tcg_thread, NULL); + timer_mod(tcg_kick_vcpu_timer, qemu_tcg_next_kick()); + } +} + +static void stop_tcg_kick_timer(void) +{ + if (tcg_kick_vcpu_timer) { + timer_del(tcg_kick_vcpu_timer); + tcg_kick_vcpu_timer = NULL; + } +} + + +/***********************************************************/ void hw_error(const char *fmt, ...) { va_list ap; @@ -1021,9 +1068,12 @@ static void qemu_wait_io_event_common(CPUState *cpu) static void qemu_tcg_wait_io_event(CPUState *cpu) { while (all_cpu_threads_idle()) { + stop_tcg_kick_timer(); qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex); } + start_tcg_kick_timer(); + while (iothread_requesting_mutex) { qemu_cond_wait(&qemu_io_proceeded_cond, &qemu_global_mutex); } @@ -1223,6 +1273,15 @@ static void deal_with_unplugged_cpus(void) } } +/* Single-threaded TCG + * + * In the single-threaded case each vCPU is simulated in turn. If + * there is more than a single vCPU we create a simple timer to kick + * the vCPU and ensure we don't get stuck in a tight loop in one vCPU. + * This is done explicitly rather than relying on side-effects + * elsewhere. + */ + static void *qemu_tcg_cpu_thread_fn(void *arg) { CPUState *cpu = arg; @@ -1249,6 +1308,8 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) } } + start_tcg_kick_timer(); + /* process any pending work */ atomic_mb_set(&exit_request, 1); -- 2.11.0