From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36139) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bHdxF-0005ff-MU for qemu-devel@nongnu.org; Mon, 27 Jun 2016 17:20:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bHdxB-0006jy-Ce for qemu-devel@nongnu.org; Mon, 27 Jun 2016 17:20:28 -0400 Received: from mail-lf0-x243.google.com ([2a00:1450:4010:c07::243]:36354) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bHdxB-0006ju-4j for qemu-devel@nongnu.org; Mon, 27 Jun 2016 17:20:25 -0400 Received: by mail-lf0-x243.google.com with SMTP id a2so30029582lfe.3 for ; Mon, 27 Jun 2016 14:20:25 -0700 (PDT) References: <1464986428-6739-1-git-send-email-alex.bennee@linaro.org> <1464986428-6739-13-git-send-email-alex.bennee@linaro.org> From: Sergey Fedorov Message-ID: <57719893.9070201@gmail.com> Date: Tue, 28 Jun 2016 00:20:19 +0300 MIME-Version: 1.0 In-Reply-To: <1464986428-6739-13-git-send-email-alex.bennee@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [RFC v3 12/19] tcg: add kick timer for single-threaded vCPU emulation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?UTF-8?Q?Alex_Benn=c3=a9e?= , mttcg@listserver.greensocs.com, qemu-devel@nongnu.org, fred.konrad@greensocs.com, a.rigo@virtualopensystems.com, cota@braap.org, bobby.prani@gmail.com Cc: mark.burton@greensocs.com, pbonzini@redhat.com, jan.kiszka@siemens.com, rth@twiddle.net, peter.maydell@linaro.org, claudio.fontana@huawei.com, Peter Crosthwaite On 03/06/16 23:40, Alex Bennée wrote: > diff --git a/cpus.c b/cpus.c > index 1694ce9..12e04c9 100644 > --- a/cpus.c > +++ b/cpus.c > @@ -1208,9 +1208,29 @@ static int tcg_cpu_exec(CPUState *cpu) > return ret; > } > > +/* 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_FREQ (qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + \ > + NANOSECONDS_PER_SECOND / 10) Hmm, it doesn't look nice to wrap calculation of the next timeout in a macro and name it '*_FREQ'. I think we'd better do like this: #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; } and use it like this: timer_mod(kick_timer, qemu_tcg_next_kick()); Kind regards, Sergey > + > +static void kick_tcg_thread(void *opaque) > +{ > + QEMUTimer *self = *(QEMUTimer **) opaque; > + timer_mod(self, TCG_KICK_FREQ); > + qemu_cpu_kick_no_halt(); > +} > + > static void *qemu_tcg_cpu_thread_fn(void *arg) > { > CPUState *cpu = arg; > + QEMUTimer *kick_timer; > > rcu_register_thread(); > > @@ -1234,6 +1254,13 @@ 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, TCG_KICK_FREQ); > + } > + > /* process any pending work */ > atomic_mb_set(&exit_request, 1); >