- Reliably align clock measurements on tick boundary before measuring.
- Use consistent timebase for time measurements in sim_idle_ms_sleep()
Windows:
- Properly restore system clock tick size on exit.
- Use highest resolution time for ms time measurements
Backed out commit 484889ea5a since the overflow of the timespec tv_nsec
field was the real cause of the problem. No need for an extra mutex.
As reported in #595
It seems that the prior use of sim_asynch_lock RECURSIVE mutex could
cause a pthread_cond_timedwait() failure with EINVAL returned.
As discussed in #595
Clock calibration normally takes several seconds to zero in on somewhat
accurate values for reasonable synchronization of simulated time to wall
clock time. Often this doesn't matter one way or another. However,
one thing which requires somewhat accurate clock calibration is the
pacing of output to serial ports on the host system. Pacing happens
at the configured bits per second rates as long as the simulators
instruction execution rate has been reasonably calibrated with respect
to wall clock time. A given host system will most likely simulate
instructions at the same rate from one run to the next, so running a
simulator for a little while and then examining the execution rate with
the SHOW CLOCK command can provide knowledge about the calibrated
execution rate which can be used to start a future simulator's execution
with a very good estimate of what the ultimate calibrated rate will be.
If the SHOW CLOCK shows simulator execution at 120,000,000 instructions
per second, and the simulated system has a simulated clock that runs at
60 hz, then the pre-calibrated values can be set with these commands:
sim> DEPOSIT INT-CLOCK TICK_SIZE_0 2000000
sim> DEPOSIT INT-CLOCK TICK_RATE_0 60
sim> DEPOSIT INT-CLOCK INTERNAL_TICK_SIZE 12000000
The INTERNAL_TIMER runs in the background whenever the simulator
doesn't have a calibrated timer running. It runs at 10 Hz.
Previously, only long delays that would transition the next clock
calibration would be coscheduled unless an explicit timer was
specified to coschedule with.
This may help with the problem discussed in #508
Without this change, timer events don't get queued correctly when the
simulator isn't running (i.e. when at the command prompt or as a consequence
of a RESET command (or during boot preparation)).
This only affects when timers are asynchronous which is not the current
default.
- Throttling delays are self adjusting for specific speed throttling
(K cycles and M cycles and % cycles).
- Throttling starts after THROT_DELAY seconds of execution.
- THROT_DELAY is a register accessible via EXAMINE and DEPOSIT
once throttling has been enabled.
- Throttle sleep times are recalibrated every 10 seconds based on
execution performance for the prior 10 seconds if the current
execution rate differs from the desired rate by more than
THROT_DRIFT_PCT. THROT_DRIFT_PCT defaults to 5 and is a
register accessible via EXAMINE and DEPOSIT once throttling has
been enabled.
- Addressing details reported in #508
Part of a previous change introduced logice which used the throttling
execution rate calibrated value to determine clock calibration when
throttling is enabled. This provides significantly worse results than the
normal self correcting calibration process. This commit reverses that
part of the previous change.
Added debug CHECK option to the sim_timer_activate_after() to verify
that coscheduled events actually have sim_activate_time_usecs() results
which are consistent with each other.
Additionally, coschedule tick processing now properly counts down
pending coschedule queued activities.
- Add support to query remaining usecs on pending events.
- Generalized the sim_interval adjustment in sim_idle to allow more than
a single decrement.
- More overhead reduction when idling.
- Carry usec values as double through out to fully support long wall clock
delays.
- Support for arbitrary long wait intervals in sim_activate_after with
precisely correct delays aligned with the calibrated clock once
per second.
- Proper handling of calls to sim_cancel for calibrated timer units
- Properly allow stopping of calibrated clock by calling sim_rtcn_calb
with a ticksper == 0
- Only schedule asynchronous timer activities for delays longer than
the minimal OS sleep time
- Only wake asynchronous timer thread to queue new timer events
that are shorter than the currently shortest scheduled event
