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i#6977: Fix quantum underflow #6973

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merged 3 commits into from
Sep 11, 2024
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Merged

i#6977: Fix quantum underflow #6973

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8e4fd76
i#6938 sched migrate: Fix quantum underflow
derekbruening Sep 6, 2024
86b1a23
Clarify comments
derekbruening Sep 10, 2024
a39ed4d
Merge branch 'master' of github.com:DynamoRIO/dynamorio into i6938-qu…
derekbruening Sep 10, 2024
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27 changes: 18 additions & 9 deletions clients/drcachesim/scheduler/scheduler.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3497,7 +3497,7 @@ scheduler_tmpl_t<RecordType, ReaderType>::next_record(output_ordinal_t output,
VPRINT(this, 4,
"next_record[%d]: input %d hit end of instr quantum\n", output,
input->index);
preempt = !need_new_input;
preempt = true;
need_new_input = true;
input->instrs_in_quantum = 0;
++outputs_[output]
Expand All @@ -3519,10 +3519,12 @@ scheduler_tmpl_t<RecordType, ReaderType>::next_record(output_ordinal_t output,
// in between (e.g., scatter/gather long sequence of reads/writes) by
// setting input->switching_pre_instruction.
record_type_is_instr_boundary(record, outputs_[output].last_record)) {
VPRINT(this, 4,
"next_record[%d]: hit end of time quantum after %" PRIu64 "\n",
output, input->time_spent_in_quantum);
preempt = !need_new_input;
VPRINT(
this, 4,
"next_record[%d]: input %d hit end of time quantum after %" PRIu64
"\n",
output, input->index, input->time_spent_in_quantum);
preempt = true;
need_new_input = true;
input->time_spent_in_quantum = 0;
++outputs_[output]
Expand Down Expand Up @@ -3553,9 +3555,10 @@ scheduler_tmpl_t<RecordType, ReaderType>::next_record(output_ordinal_t output,
res != sched_type_t::STATUS_SKIPPED)
return res;
if (outputs_[output].cur_input != prev_input) {
// TODO i#5843: Queueing here and in a few other places gets the
// ordinals off: we need to undo the ordinal increases to avoid
// over-counting while queued and double-counting when we resume.
// TODO i#5843: Queueing here and in a few other places gets the stream
// record and instruction ordinals off: we need to undo the ordinal
// increases to avoid over-counting while queued and double-counting
// when we resume.
// In some cases we need to undo this on the output stream too.
// So we should set suppress_ref_count_ in the input to get
// is_record_synthetic() (and have our stream class check that
Expand All @@ -3564,12 +3567,18 @@ scheduler_tmpl_t<RecordType, ReaderType>::next_record(output_ordinal_t output,
lock.lock();
VPRINT(this, 5, "next_record_mid[%d]: switching from %d to %d\n", output,
prev_input, outputs_[output].cur_input);
if (!preempt) {
// We need to offset the {instrs,time_spent}_in_quantum values from
// overshooting during dynamic scheduling, unless this is a preempt when
// we've already reset to 0.
if (!preempt && options_.mapping == MAP_TO_ANY_OUTPUT) {
if (options_.quantum_unit == QUANTUM_INSTRUCTIONS &&
record_type_is_instr_boundary(record,
outputs_[output].last_record)) {
assert(inputs_[prev_input].instrs_in_quantum > 0);
--inputs_[prev_input].instrs_in_quantum;
} else if (options_.quantum_unit == QUANTUM_TIME) {
assert(inputs_[prev_input].time_spent_in_quantum >=
cur_time - prev_time_in_quantum);
inputs_[prev_input].time_spent_in_quantum -=
(cur_time - prev_time_in_quantum);
}
Expand Down
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