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Always deliver the sample IP.

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Add PERF_SAMPLE_IP to the callstack sample: for code compiled without
frame pointers the kernel delivers no user stack, and such samples were
dropped entirely. When the callchain count is zero, synthesize a
one-frame trace holding just the leaf IP.
This commit is contained in:
Bartosz Taudul
2026-08-30 16:22:18 +02:00
parent afe1ec5faf
commit 37410933db
1 changed files with 21 additions and 17 deletions
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38
public/client/TracySysTrace.cpp
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@@ -863,7 +863,7 @@ bool SysTraceStart( int64_t& samplingPeriod )
pe.size = sizeof( perf_event_attr );
pe.config = PERF_COUNT_SW_CPU_CLOCK;
pe.sample_freq = samplingFrequency;
pe.sample_type = PERF_SAMPLE_TID | PERF_SAMPLE_TIME | PERF_SAMPLE_CALLCHAIN;
pe.sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_TID | PERF_SAMPLE_TIME | PERF_SAMPLE_CALLCHAIN;
#if LINUX_VERSION_CODE >= KERNEL_VERSION( 4, 8, 0 )
if( perfAbi >= PerfAbi48AndNewer ) pe.sample_max_stack = 127;
#endif
@@ -1187,38 +1187,42 @@ void SysTraceWorker( void* ptr )
{
auto offset = pos + sizeof( perf_event_header );
// Layout:
// u32 pid, tid
// u64 time
// u64 cnt
// u64 ip[cnt]
// field order matches PERF_SAMPLE_IP | TID | TIME | CALLCHAIN (then buf.cnt ips)
#pragma pack( push, 1 )
struct
{
uint64_t ip;
uint32_t pid;
uint32_t tid;
uint64_t t0;
uint64_t cnt;
} buf;
#pragma pack( pop )
offset += sizeof( uint32_t );
ring.Read( &buf, offset, sizeof( buf ) );
offset += sizeof( buf );
uint64_t* trace;
if( buf.cnt > 0 )
{
#if defined TRACY_HW_TIMER && defined TRACY_HAS_RDTSC
buf.t0 = ring.ConvertTimeToTsc( buf.t0 );
#endif
auto trace = GetCallstackBlock( buf.cnt, ring, offset );
TracyLfqPrepare( QueueType::CallstackSample );
MemWrite( &item->callstackSampleFat.time, int64_t( buf.t0 ) );
MemWrite( &item->callstackSampleFat.thread, buf.tid );
MemWrite( &item->callstackSampleFat.ptr, uint64_t( trace ) );
TracyLfqCommit;
trace = GetCallstackBlock( buf.cnt, ring, offset );
}
else
{
trace = (uint64_t*)tracy_malloc_fast( 2 * sizeof( uint64_t ) );
trace[0] = 1;
trace[1] = buf.ip;
}
#if defined TRACY_HW_TIMER && defined TRACY_HAS_RDTSC
buf.t0 = ring.ConvertTimeToTsc( buf.t0 );
#endif
TracyLfqPrepare( QueueType::CallstackSample );
MemWrite( &item->callstackSampleFat.time, int64_t( buf.t0 ) );
MemWrite( &item->callstackSampleFat.thread, buf.tid );
MemWrite( &item->callstackSampleFat.ptr, uint64_t( trace ) );
TracyLfqCommit;
}
pos += hdr.size;
}