From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57454) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bXrqZ-0003iQ-TV for qemu-devel@nongnu.org; Thu, 11 Aug 2016 11:24:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bXrqX-0006cS-RL for qemu-devel@nongnu.org; Thu, 11 Aug 2016 11:24:38 -0400 Received: from mail-wm0-x236.google.com ([2a00:1450:400c:c09::236]:38813) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bXrqX-0006cL-LX for qemu-devel@nongnu.org; Thu, 11 Aug 2016 11:24:37 -0400 Received: by mail-wm0-x236.google.com with SMTP id o80so3120530wme.1 for ; Thu, 11 Aug 2016 08:24:37 -0700 (PDT) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= Date: Thu, 11 Aug 2016 16:24:10 +0100 Message-Id: <1470929064-4092-15-git-send-email-alex.bennee@linaro.org> In-Reply-To: <1470929064-4092-1-git-send-email-alex.bennee@linaro.org> References: <1470929064-4092-1-git-send-email-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [Qemu-devel] [RFC v4 14/28] tcg: add kick timer for single-threaded vCPU emulation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: mttcg@listserver.greensocs.com, qemu-devel@nongnu.org, fred.konrad@greensocs.com, a.rigo@virtualopensystems.com, cota@braap.org, bobby.prani@gmail.com, nikunj@linux.vnet.ibm.com Cc: mark.burton@greensocs.com, pbonzini@redhat.com, jan.kiszka@siemens.com, serge.fdrv@gmail.com, rth@twiddle.net, peter.maydell@linaro.org, claudio.fontana@huawei.com, =?UTF-8?q?Alex=20Benn=C3=A9e?= , Peter Crosthwaite 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 --- v2 - re-base fixes - get_ticks_per_sec() -> NANOSECONDS_PER_SEC v3 - add define for TCG_KICK_FREQ - fix checkpatch warning v4 - wrap next calc in inline qemu_tcg_next_kick() instead of macro --- cpus.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/cpus.c b/cpus.c index b5b45b8..8c49d6c 100644 --- a/cpus.c +++ b/cpus.c @@ -1185,9 +1185,34 @@ 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_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) +{ + QEMUTimer *self = *(QEMUTimer **) opaque; + timer_mod(self, qemu_tcg_next_kick()); + qemu_cpu_kick_no_halt(); +} + static void *qemu_tcg_cpu_thread_fn(void *arg) { CPUState *cpu = arg; + QEMUTimer *kick_timer; rcu_register_thread(); @@ -1211,6 +1236,13 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) } } + /* Set to kick if we have to do more than one vCPU */ + if (CPU_NEXT(first_cpu)) { + kick_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, kick_tcg_thread, + &kick_timer); + timer_mod(kick_timer, qemu_tcg_next_kick()); + } + /* process any pending work */ atomic_mb_set(&exit_request, 1); -- 2.7.4