| Message ID | 20170127103922.19658-7-alex.bennee@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Remaining MTTCG Base patches and ARM enablement | expand |
Alex Bennée writes: > 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 <alex.bennee@linaro.org> > Reviewed-by: Richard Henderson <rth@twiddle.net> > --- > 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 > v5 > - move all kick code into own section > - use global for timer > - add helper functions to start/stop timer > - stop timer when all cores paused > v7 > - checkpatch > 80 char fix > --- > cpus.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 61 insertions(+) > > diff --git a/cpus.c b/cpus.c > index 76b6e04332..a98925105c 100644 > --- a/cpus.c > +++ b/cpus.c > @@ -767,6 +767,53 @@ 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. s/with/will/ > + * > + * 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; > @@ -1020,9 +1067,12 @@ 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); > } > @@ -1222,6 +1272,15 @@ 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; > @@ -1248,6 +1307,8 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) > } > } > > + start_tcg_kick_timer(); > + > /* process any pending work */ > atomic_mb_set(&exit_request, 1); Reviewed-by: Pranith Kumar <bobby.prani@gmail.com> Thanks, -- Pranith
diff --git a/cpus.c b/cpus.c index 76b6e04332..a98925105c 100644 --- a/cpus.c +++ b/cpus.c @@ -767,6 +767,53 @@ 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; @@ -1020,9 +1067,12 @@ 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); } @@ -1222,6 +1272,15 @@ 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; @@ -1248,6 +1307,8 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) } } + start_tcg_kick_timer(); + /* process any pending work */ atomic_mb_set(&exit_request, 1);