@@ -65,7 +65,7 @@ typedef enum {
* QEMU_TIMER_ATTR_EXTERNAL: drives external subsystem
*
* Timers with this attribute do not recorded in rr mode, therefore it could be
- * used for the subsystems that operate outside the guest core. Applicable only
+ * used for the subsystems that operate outside the guest core. Relevant only
* with virtual clock type.
*/
@@ -490,6 +490,7 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
QEMUTimerCB *cb;
void *opaque;
bool need_replay_checkpoint = false;
+ ReplayCheckpoint replay_checkpoint_id = (ReplayCheckpoint)-1;
if (!atomic_read(&timer_list->active_timers)) {
return false;
@@ -500,43 +501,40 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
goto out;
}
- switch (timer_list->clock->type) {
- case QEMU_CLOCK_REALTIME:
- break;
- default:
- case QEMU_CLOCK_VIRTUAL:
- if (replay_mode != REPLAY_MODE_NONE) {
- /* Checkpoint for virtual clock is redundant in cases where
- * it's being triggered with only non-EXTERNAL timers, because
- * these timers don't change guest state directly.
- * Since it has conditional dependence on specific timers, it is
- * subject to race conditions and requires special handling.
- * See below.
- */
+ if (replay_mode != REPLAY_MODE_NONE) {
+ /* Postpone actual checkpointing to timer list processing
+ * to properly check if we actually need it.
+ */
+ switch (timer_list->clock->type) {
+ case QEMU_CLOCK_VIRTUAL:
need_replay_checkpoint = true;
+ replay_checkpoint_id = CHECKPOINT_CLOCK_VIRTUAL;
+ break;
+ case QEMU_CLOCK_HOST:
+ need_replay_checkpoint = true;
+ replay_checkpoint_id = CHECKPOINT_CLOCK_HOST;
+ break;
+ case QEMU_CLOCK_VIRTUAL_RT:
+ need_replay_checkpoint = true;
+ replay_checkpoint_id = CHECKPOINT_CLOCK_VIRTUAL_RT;
+ break;
+ default:
+ break;
}
- break;
- case QEMU_CLOCK_HOST:
- if (!replay_checkpoint(CHECKPOINT_CLOCK_HOST)) {
- goto out;
- }
- break;
- case QEMU_CLOCK_VIRTUAL_RT:
- if (!replay_checkpoint(CHECKPOINT_CLOCK_VIRTUAL_RT)) {
- goto out;
- }
- break;
}
/*
- * Extract expired timers from active timers list and and process them.
+ * Extract expired timers from active timers list and and process them,
+ * taking into account checkpointing required in rr mode.
*
- * In rr mode we need "filtered" checkpointing for virtual clock.
- * Checkpoint must be replayed before any non-EXTERNAL timer has been
- * processed and only one time (virtual clock value stays same). But these
- * timers may appear in the timers list while it being processed, so this
- * must be checked until we finally decide that "no timers left - we are
- * done".
+ * Checkpoint must be replayed before any timer has been processed
+ * and only one time. But new timers may appear in the timers list while
+ * it's being processed, so this must be checked until we finally decide
+ * that "no timers left - we are done" (to avoid skipping checkpoint due to
+ * possible races).
+ * Also checkpoint for virtual clock is redundant in cases where it's being
+ * triggered with only non-EXTERNAL timers, because these timers don't
+ * change guest state directly.
*/
current_time = qemu_clock_get_ns(timer_list->clock->type);
qemu_mutex_lock(&timer_list->active_timers_lock);
@@ -552,7 +550,7 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
/* once we got here, checkpoint clock only once */
need_replay_checkpoint = false;
qemu_mutex_unlock(&timer_list->active_timers_lock);
- if (!replay_checkpoint(CHECKPOINT_CLOCK_VIRTUAL)) {
+ if (!replay_checkpoint(replay_checkpoint_id)) {
goto out;
}
qemu_mutex_lock(&timer_list->active_timers_lock);
Removes redundant checkpoints in replay log when there are no expired timers in timers list, associated with corresponding clock (i.e. no rr events associated with current clock value). This also improves performance in rr mode. Signed-off-by: Artem Pisarenko <artem.k.pisarenko@gmail.com> --- Oops and again oops. Now it finally should be fine... v3: - fixed compiler warning caused non-debug build to fail include/qemu/timer.h | 2 +- util/qemu-timer.c | 62 +++++++++++++++++++++++++--------------------------- 2 files changed, 31 insertions(+), 33 deletions(-)