Message ID | 1381222058-16701-9-git-send-email-pbonzini@redhat.com |
---|---|
State | New |
Headers | show |
On 8 Oct 2013, at 09:47, Paolo Bonzini wrote: > This lets threads other than the I/O thread use vm_clock even in -icount mode. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Looks good to me Alex > --- > cpus.c | 42 ++++++++++++++++++++++++++++++++++-------- > 1 file changed, 34 insertions(+), 8 deletions(-) > > diff --git a/cpus.c b/cpus.c > index bc675a4..1e5cba4 100644 > --- a/cpus.c > +++ b/cpus.c > @@ -133,7 +133,7 @@ typedef struct TimersState { > static TimersState timers_state; > > /* Return the virtual CPU time, based on the instruction counter. */ > -int64_t cpu_get_icount(void) > +static int64_t cpu_get_icount_locked(void) > { > int64_t icount; > CPUState *cpu = current_cpu; > @@ -149,6 +149,19 @@ int64_t cpu_get_icount(void) > return qemu_icount_bias + (icount << icount_time_shift); > } > > +int64_t cpu_get_icount(void) > +{ > + int64_t icount; > + unsigned start; > + > + do { > + start = seqlock_read_begin(&timers_state.clock_seqlock); > + icount = cpu_get_icount_locked(); > + } while (seqlock_read_retry(&timers_state.clock_seqlock, start)); > + > + return icount; > +} > + > /* return the host CPU cycle counter and handle stop/restart */ > /* cpu_ticks is safely if holding BQL */ > int64_t cpu_get_ticks(void) > @@ -246,8 +259,9 @@ static void icount_adjust(void) > return; > } > > - cur_time = cpu_get_clock(); > - cur_icount = cpu_get_icount(); > + seqlock_write_lock(&timers_state.clock_seqlock); > + cur_time = cpu_get_clock_locked(); > + cur_icount = cpu_get_icount_locked(); > > delta = cur_icount - cur_time; > /* FIXME: This is a very crude algorithm, somewhat prone to oscillation. */ > @@ -265,6 +279,7 @@ static void icount_adjust(void) > } > last_delta = delta; > qemu_icount_bias = cur_icount - (qemu_icount << icount_time_shift); > + seqlock_write_unlock(&timers_state.clock_seqlock); > } > > static void icount_adjust_rt(void *opaque) > @@ -289,10 +304,14 @@ static int64_t qemu_icount_round(int64_t count) > > static void icount_warp_rt(void *opaque) > { > - if (vm_clock_warp_start == -1) { > + /* The icount_warp_timer is rescheduled soon after vm_clock_warp_start > + * changes from -1 to another value, so the race here is okay. > + */ > + if (atomic_read(&vm_clock_warp_start) == -1) { > return; > } > > + seqlock_write_lock(&timers_state.clock_seqlock); > if (runstate_is_running()) { > int64_t clock = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); > int64_t warp_delta; > @@ -303,14 +322,15 @@ static void icount_warp_rt(void *opaque) > * In adaptive mode, do not let QEMU_CLOCK_VIRTUAL run too > * far ahead of real time. > */ > - int64_t cur_time = cpu_get_clock(); > - int64_t cur_icount = cpu_get_icount(); > + int64_t cur_time = cpu_get_clock_locked(); > + int64_t cur_icount = cpu_get_icount_locked(); > int64_t delta = cur_time - cur_icount; > warp_delta = MIN(warp_delta, delta); > } > qemu_icount_bias += warp_delta; > } > vm_clock_warp_start = -1; > + seqlock_write_unlock(&timers_state.clock_seqlock); > > if (qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) { > qemu_clock_notify(QEMU_CLOCK_VIRTUAL); > @@ -324,7 +344,10 @@ void qtest_clock_warp(int64_t dest) > while (clock < dest) { > int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL); > int64_t warp = MIN(dest - clock, deadline); > + seqlock_write_lock(&timers_state.clock_seqlock); > qemu_icount_bias += warp; > + seqlock_write_unlock(&timers_state.clock_seqlock); > + > qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL); > clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); > } > @@ -391,9 +415,11 @@ void qemu_clock_warp(QEMUClockType type) > * you will not be sending network packets continuously instead of > * every 100ms. > */ > + seqlock_write_lock(&timers_state.clock_seqlock); > if (vm_clock_warp_start == -1 || vm_clock_warp_start > clock) { > vm_clock_warp_start = clock; > } > + seqlock_write_unlock(&timers_state.clock_seqlock); > timer_mod_anticipate(icount_warp_timer, clock + deadline); > } else if (deadline == 0) { > qemu_clock_notify(QEMU_CLOCK_VIRTUAL); > -- > 1.8.3.1 > > >
diff --git a/cpus.c b/cpus.c index bc675a4..1e5cba4 100644 --- a/cpus.c +++ b/cpus.c @@ -133,7 +133,7 @@ typedef struct TimersState { static TimersState timers_state; /* Return the virtual CPU time, based on the instruction counter. */ -int64_t cpu_get_icount(void) +static int64_t cpu_get_icount_locked(void) { int64_t icount; CPUState *cpu = current_cpu; @@ -149,6 +149,19 @@ int64_t cpu_get_icount(void) return qemu_icount_bias + (icount << icount_time_shift); } +int64_t cpu_get_icount(void) +{ + int64_t icount; + unsigned start; + + do { + start = seqlock_read_begin(&timers_state.clock_seqlock); + icount = cpu_get_icount_locked(); + } while (seqlock_read_retry(&timers_state.clock_seqlock, start)); + + return icount; +} + /* return the host CPU cycle counter and handle stop/restart */ /* cpu_ticks is safely if holding BQL */ int64_t cpu_get_ticks(void) @@ -246,8 +259,9 @@ static void icount_adjust(void) return; } - cur_time = cpu_get_clock(); - cur_icount = cpu_get_icount(); + seqlock_write_lock(&timers_state.clock_seqlock); + cur_time = cpu_get_clock_locked(); + cur_icount = cpu_get_icount_locked(); delta = cur_icount - cur_time; /* FIXME: This is a very crude algorithm, somewhat prone to oscillation. */ @@ -265,6 +279,7 @@ static void icount_adjust(void) } last_delta = delta; qemu_icount_bias = cur_icount - (qemu_icount << icount_time_shift); + seqlock_write_unlock(&timers_state.clock_seqlock); } static void icount_adjust_rt(void *opaque) @@ -289,10 +304,14 @@ static int64_t qemu_icount_round(int64_t count) static void icount_warp_rt(void *opaque) { - if (vm_clock_warp_start == -1) { + /* The icount_warp_timer is rescheduled soon after vm_clock_warp_start + * changes from -1 to another value, so the race here is okay. + */ + if (atomic_read(&vm_clock_warp_start) == -1) { return; } + seqlock_write_lock(&timers_state.clock_seqlock); if (runstate_is_running()) { int64_t clock = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); int64_t warp_delta; @@ -303,14 +322,15 @@ static void icount_warp_rt(void *opaque) * In adaptive mode, do not let QEMU_CLOCK_VIRTUAL run too * far ahead of real time. */ - int64_t cur_time = cpu_get_clock(); - int64_t cur_icount = cpu_get_icount(); + int64_t cur_time = cpu_get_clock_locked(); + int64_t cur_icount = cpu_get_icount_locked(); int64_t delta = cur_time - cur_icount; warp_delta = MIN(warp_delta, delta); } qemu_icount_bias += warp_delta; } vm_clock_warp_start = -1; + seqlock_write_unlock(&timers_state.clock_seqlock); if (qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) { qemu_clock_notify(QEMU_CLOCK_VIRTUAL); @@ -324,7 +344,10 @@ void qtest_clock_warp(int64_t dest) while (clock < dest) { int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL); int64_t warp = MIN(dest - clock, deadline); + seqlock_write_lock(&timers_state.clock_seqlock); qemu_icount_bias += warp; + seqlock_write_unlock(&timers_state.clock_seqlock); + qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL); clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); } @@ -391,9 +415,11 @@ void qemu_clock_warp(QEMUClockType type) * you will not be sending network packets continuously instead of * every 100ms. */ + seqlock_write_lock(&timers_state.clock_seqlock); if (vm_clock_warp_start == -1 || vm_clock_warp_start > clock) { vm_clock_warp_start = clock; } + seqlock_write_unlock(&timers_state.clock_seqlock); timer_mod_anticipate(icount_warp_timer, clock + deadline); } else if (deadline == 0) { qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
This lets threads other than the I/O thread use vm_clock even in -icount mode. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- cpus.c | 42 ++++++++++++++++++++++++++++++++++-------- 1 file changed, 34 insertions(+), 8 deletions(-)