Bug report
Bug description:
Found while profiling the whole -m test...
There are two issues here:
Invalid RLE count- incorrect samples count (
129088 v. 129091)
Real reproduction that I encountered
[1] 2026-05-04T03:23:50.414056000+0200 maurycy@gimel /Users/maurycy/src/github.com/maurycy/cpython (main 2e94f14) % sudo -E /Users/maurycy/src/github.com/maurycy/cpython/python.exe \
-m profiling.sampling run \
--sampling-rate 1000000 \
--duration 60 \
--binary -o /tmp/repro.bin \
-m test test_asyncio.test_base_events
Using random seed: 1964393136
0:00:00 load avg: 2.44 Run 1 test sequentially in a single process
0:00:00 load avg: 2.44 [1/1] test_asyncio.test_base_events
0:00:01 load avg: 2.32 [1/1] test_asyncio.test_base_events passed
== Tests result: SUCCESS ==
1 test OK.
Total duration: 1.5 sec
Total tests: run=116 skipped=1
Total test files: run=1/1
Result: SUCCESS
Captured 143,113 samples in 1.57 seconds
Sample rate: 91,375.80 samples/sec
Error rate: 9.80
Binary Encoding:
Records: 12,013
RLE repeat: 1,023 (8.5%) [118,098 samples]
Full stack: 3 (0.0%)
Suffix match: 1,513 (12.6%)
Pop-push: 9,474 (78.9%)
Frame Efficiency:
Frames written: 24,428
Frames saved: 4,717,911 (99.5%)
Bytes (pre-zstd): 473.3 KB
Warning: missed 1423089 samples from the expected total of 1566202 (90.86%)
Binary profile written to /tmp/repro.bin (129088 samples)
2026-05-04T03:23:52.834435000+0200 maurycy@gimel /Users/maurycy/src/github.com/maurycy/cpython (main 2e94f14) % /Users/maurycy/src/github.com/maurycy/cpython/python.exe \
-m profiling.sampling replay --collapsed \
-o /tmp/out.collapsed /tmp/repro.bin
Replaying 129091 samples from /tmp/repro.bin
Sample interval: 1 us
Compression: zstd
[███████████████████████████████████████░] 100.0% (129,066/129,091)Error: Invalid RLE count 1566628 exceeds maximum possible 10 for remaining dataRepro from my dump
2026-05-04T03:28:27.980622000+0200 maurycy@gimel /Users/maurycy/work/cpython (main 2e94f14) % curl -sL https://gist.githubusercontent.com/maurycy/ca583d26ddf87794c8d25c9719786940/raw | base64 -d > repro.bin
2026-05-04T03:28:33.775531000+0200 maurycy@gimel /Users/maurycy/work/cpython (main 2e94f14?) % ./python.exe -m profiling.sampling replay --collapsed -o /tmp/out.collapsed repro.bin
Replaying 129091 samples from repro.bin
Sample interval: 1 us
Compression: zstd
[███████████████████████████████████████░] 100.0% (129,066/129,091)Error: Invalid RLE count 1566628 exceeds maximum possible 10 for remaining data
Targeted reproduction
import _remote_debugging
w = _remote_debugging.BinaryWriter('/tmp/test.bin', 1, 1000000, compression=0)
loc = _remote_debugging.LocationInfo((10, 10, 0, 0))
fi = _remote_debugging.FrameInfo(('foo.py', loc, 'bar', None))
w.write_sample([_remote_debugging.InterpreterInfo((0, [_remote_debugging.ThreadInfo((12345, 1, [fi]))]))], 1000001)
# new thread with empty stack...
try:
w.write_sample([_remote_debugging.InterpreterInfo((0, [_remote_debugging.ThreadInfo((99999, 4, []))]))], 1000004)
except RuntimeError as e:
print(e) # "Invalid stack encoding type" - smashed already.CPython versions tested on:
CPython main branch
Operating systems tested on:
macOS
Linked PRs
Bug report
Bug description:
Found while profiling the whole
-m test...There are two issues here:
Invalid RLE count129088v.129091)Real reproduction that I encountered
[1] 2026-05-04T03:23:50.414056000+0200 maurycy@gimel /Users/maurycy/src/github.com/maurycy/cpython (main 2e94f14) % sudo -E /Users/maurycy/src/github.com/maurycy/cpython/python.exe \ -m profiling.sampling run \ --sampling-rate 1000000 \ --duration 60 \ --binary -o /tmp/repro.bin \ -m test test_asyncio.test_base_events Using random seed: 1964393136 0:00:00 load avg: 2.44 Run 1 test sequentially in a single process 0:00:00 load avg: 2.44 [1/1] test_asyncio.test_base_events 0:00:01 load avg: 2.32 [1/1] test_asyncio.test_base_events passed == Tests result: SUCCESS == 1 test OK. Total duration: 1.5 sec Total tests: run=116 skipped=1 Total test files: run=1/1 Result: SUCCESS Captured 143,113 samples in 1.57 seconds Sample rate: 91,375.80 samples/sec Error rate: 9.80 Binary Encoding: Records: 12,013 RLE repeat: 1,023 (8.5%) [118,098 samples] Full stack: 3 (0.0%) Suffix match: 1,513 (12.6%) Pop-push: 9,474 (78.9%) Frame Efficiency: Frames written: 24,428 Frames saved: 4,717,911 (99.5%) Bytes (pre-zstd): 473.3 KB Warning: missed 1423089 samples from the expected total of 1566202 (90.86%) Binary profile written to /tmp/repro.bin (129088 samples) 2026-05-04T03:23:52.834435000+0200 maurycy@gimel /Users/maurycy/src/github.com/maurycy/cpython (main 2e94f14) % /Users/maurycy/src/github.com/maurycy/cpython/python.exe \ -m profiling.sampling replay --collapsed \ -o /tmp/out.collapsed /tmp/repro.bin Replaying 129091 samples from /tmp/repro.bin Sample interval: 1 us Compression: zstd [███████████████████████████████████████░] 100.0% (129,066/129,091)Error: Invalid RLE count 1566628 exceeds maximum possible 10 for remaining dataRepro from my dump
Targeted reproduction
CPython versions tested on:
CPython main branch
Operating systems tested on:
macOS
Linked PRs
_remote_debugging: Fix binary profile corruption when sampling a (temporarily) empty stack #149343