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i#2039 trace trim, part 5: Drop early data #5768

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merged 2 commits into from
Dec 1, 2022
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i#2039 trace trim, part 5: Drop early data #5768

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156faad
i#2039 trace trim, part 5: Drop early data
derekbruening Nov 30, 2022
92b4afb
Add verbose output for attach timestamp and replacements and drops
derekbruening Nov 30, 2022
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2 changes: 2 additions & 0 deletions clients/drcachesim/tracer/instru_offline.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -412,6 +412,8 @@ offline_instru_t::refresh_unit_header_timestamp(byte *buf_ptr, uint64 min_timest
offline_entry_t *stamp = reinterpret_cast<offline_entry_t *>(buf_ptr);
DR_ASSERT(stamp->timestamp.type == OFFLINE_TYPE_TIMESTAMP);
if (stamp->timestamp.usec < min_timestamp) {
log_(2, "%s: replacing " UINT64_FORMAT_STRING " with " UINT64_FORMAT_STRING "\n",
__FUNCTION__, stamp->timestamp.usec, min_timestamp);
stamp->timestamp.usec = min_timestamp;
return true;
}
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12 changes: 10 additions & 2 deletions clients/drcachesim/tracer/output.cpp
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Expand Up @@ -918,7 +918,6 @@ process_and_output_buffer(void *drcontext, bool skip_size_cap)
// the first buffer.
if (data->has_thread_header && op_offline.get_value())
header_size += data->init_header_size;
data->has_thread_header = false;

if (align_attach_detach_endpoints()) {
// This is the attach counterpart to instru_t::set_frozen_timestamp(): we place
Expand All @@ -927,12 +926,21 @@ process_and_output_buffer(void *drcontext, bool skip_size_cap)
// tracing. (Switching back to timestamps at buffer output is actually
// worse as we then have the identical frozen timestamp for all the flushes
// during detach, plus they are all on the same cpu too.)
uint64 min_timestamp = attached_timestamp.load(std::memory_order_acquire);
if (min_timestamp == 0) {
// This data is too early: we drop it.
NOTIFY(1, "Dropping too-early data for T%zd\n", dr_get_thread_id(drcontext));
BUF_PTR(data->seg_base) = data->buf_base + header_size;
return;
}
size_t stamp_offs =
header_size > buf_hdr_slots_size ? header_size - buf_hdr_slots_size : 0;
uint64 min_timestamp = attached_timestamp.load(std::memory_order_acquire);
instru->refresh_unit_header_timestamp(data->buf_base + stamp_offs, min_timestamp);
}

// Clear after we know we're not dropping for align_attach_detach_endpoints.
data->has_thread_header = false;

buf_ptr = BUF_PTR(data->seg_base);
// We may get called with nothing to write: e.g., on a syscall for
// -L0I_filter and -L0D_filter.
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4 changes: 3 additions & 1 deletion clients/drcachesim/tracer/tracer.cpp
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Expand Up @@ -416,7 +416,9 @@ event_post_attach()
DR_ASSERT(attached_midway);
if (!align_attach_detach_endpoints())
return;
attached_timestamp.store(instru_t::get_timestamp(), std::memory_order_release);
uint64 timestamp = instru_t::get_timestamp();
attached_timestamp.store(timestamp, std::memory_order_release);
NOTIFY(1, "Fully-attached timestamp is " UINT64_FORMAT_STRING "\n", timestamp);
if (op_trace_after_instrs.get_value() != 0) {
NOTIFY(1, "Switching to counting mode after attach\n");
tracing_mode.store(BBDUP_MODE_COUNT, std::memory_order_release);
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