feat: sub-interpreters support

[P403n1x87]

Description of the Change

We add support for sub-interpreters. With this change we loop over the linked list of sub-interpreters and sample them in turn. With PEP 554 and PEP 684, we foresee a potential growing interest into sub-interpreters. Therefore we add support for sub-interpreters to Austin to make it future-proof, at no extra performance cost for the single interpreter scenario.

Extra sub-interpreter identification information is carried by the Stack MOJO event. For the collapsed stack format, we add a prefix to the thread identifier, which represents the sub-interpreter ID. The main interpreter is identified by the 0 ID.

Alternate Designs

None considered.

Regressions

None expected

Verification Process

Added an extra test case to verify that we get the extra sub-interpreter identification information.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.53% 🎉

Comparison is base (068dd8b) 68.14% compared to head (c43198d) 68.68%.

Additional details and impacted files

@@            Coverage Diff             @@
##            devel     #198      +/-   ##
==========================================
+ Coverage   68.14%   68.68%   +0.53%     
==========================================
  Files          27       27              
  Lines        2518     2523       +5     
  Branches      773      775       +2     
==========================================
+ Hits         1716     1733      +17     
+ Misses        464      458       -6     
+ Partials      338      332       -6     

Files Changed	Coverage Δ
src/argparse.c	60.27% <ø> (ø)
src/mojo.h	100.00% <ø> (ø)
src/version.h	60.00% <ø> (ø)
src/py_proc.c	66.20% <100.00%> (+1.09%)	⬆️
src/py_thread.c	73.09% <100.00%> (+1.33%)	⬆️

... and 1 file with indirect coverage changes

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[github-actions]

Austin Benchmarks

Running Austin benchmarks with Python 3.10.13

Benchmark Summary

Comparison of dev against 3.5.0.

The following scenarios show a statistically significant difference in performance between the two versions.

	Sample Rate	Saturation	Error Rate	Sampling Speed
CPU time [sampling interval: 100]	🟡	🟢	🟡	🟡
RSA keygen [sampling interval: 10]	🔴	🟡	🟡	🔴
RSA keygen [sampling interval: 100]	🟡	🟡	🟢	🟡

Benchmark Results

Wall time [sampling interval: 1]

Wall time [sampling interval: 1]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	119000 ± 4000	1 ± 0	8e-06 ± 5e-06	13.0 ± 0.5
3.5.0	120000 ± 2000	1 ± 0	9e-06 ± 4e-06	13 ± 0
dev	121000 ± 2000	1 ± 0	7e-06 ± 2e-06	12.8 ± 0.4

Wall time [sampling interval: 10]

Wall time [sampling interval: 10]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	117000 ± 4000	0.543 ± 0.002	8e-06 ± 4e-06	13.1 ± 0.3
3.5.0	119000 ± 3000	0.544 ± 0.001	6e-06 ± 3e-06	13 ± 0
dev	119000 ± 3000	0.544 ± 0.002	8e-06 ± 4e-06	13 ± 0

Wall time [sampling interval: 100]

Wall time [sampling interval: 100]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	10600 ± 400	0.0009 ± 0.0003	2e-05 ± 3e-05	15.3 ± 0.7
3.5.0	10900 ± 500	0.0008 ± 0.0002	2e-05 ± 4e-05	14.3 ± 0.7
dev	10600 ± 300	0.0006 ± 0.0002	2e-05 ± 2e-05	14.5 ± 0.5

Wall time [sampling interval: 1000]

Wall time [sampling interval: 1000]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	1860 ± 20	0.0002 ± 0.0003	0.0001 ± 0.0001	18 ± 2
3.5.0	1870 ± 20	0.0001 ± 0.0002	0.0001 ± 0.0001	19 ± 1
dev	1860 ± 20	0.0001 ± 0.0003	4e-05 ± 8e-05	19 ± 1

CPU time [sampling interval: 1]

CPU time [sampling interval: 1]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	53000 ± 2000	1 ± 0	1.2e-05 ± 8e-06	22.7 ± 0.5
3.5.0	53000 ± 2000	1 ± 0	1.6e-05 ± 8e-06	22.7 ± 0.8
dev	51000 ± 4000	1 ± 0	1.1e-05 ± 6e-06	22.8 ± 0.9

CPU time [sampling interval: 10]

CPU time [sampling interval: 10]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	51000 ± 2000	0.9982 ± 0.0002	1.2e-05 ± 1e-05	23.0 ± 0.7
3.5.0	52000 ± 3000	0.9984 ± 0.0001	1.1e-05 ± 8e-06	22.7 ± 0.9
dev	53000 ± 2000	0.998 ± 0.0007	1.2e-05 ± 7e-06	22.7 ± 0.7

CPU time [sampling interval: 100]

CPU time [sampling interval: 100]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	5370 ± 90	0.0011 ± 0.0002	7e-05 ± 8e-05	23.5 ± 0.7
3.5.0	5360 ± 90	0.0015 ± 0.0003	3e-05 ± 5e-05	23.8 ± 0.6
dev	5400 ± 100	0.0011 ± 0.0002	6e-05 ± 7e-05	23.8 ± 0.8

CPU time [sampling interval: 1000]

CPU time [sampling interval: 1000]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	948 ± 5	0.0002 ± 0.0004	0 ± 0	30 ± 2
3.5.0	946 ± 3	0.0004 ± 0.0007	0.0001 ± 0.0002	30 ± 2
dev	946 ± 3	0.0004 ± 0.0005	0.0001 ± 0.0002	30 ± 2

RSA keygen [sampling interval: 1]

RSA keygen [sampling interval: 1]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	39100 ± 1000	1 ± 0	0.0002 ± 0.0001	24.8 ± 0.4
3.5.0	38000 ± 2000	1 ± 0	0.0003 ± 0.0003	25.1 ± 0.7
dev	39000 ± 500	1 ± 0	0.0003 ± 0.0001	25.1 ± 0.3

RSA keygen [sampling interval: 10]

RSA keygen [sampling interval: 10]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	39000 ± 2000	0.98 ± 0.01	0.0003 ± 0.0002	25 ± 1
3.5.0	40000 ± 1000	0.988 ± 0.006	0.00015 ± 7e-05	24.1 ± 1.0
dev	39000 ± 900	0.97 ± 0.03	0.0003 ± 0.0004	25.1 ± 0.6

RSA keygen [sampling interval: 100]

RSA keygen [sampling interval: 100]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	6300 ± 30	0.004 ± 0.004	0.0007 ± 0.0007	29 ± 2
3.5.0	6300 ± 20	0.003 ± 0.003	0.0008 ± 0.0007	28 ± 1
dev	6260 ± 80	0.003 ± 0.003	0.0003 ± 0.0003	29 ± 2

RSA keygen [sampling interval: 1000]

RSA keygen [sampling interval: 1000]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	940 ± 3	0 ± 0	0.001 ± 0.001	36 ± 3
3.5.0	939 ± 5	0.0002 ± 0.0005	0.0003 ± 0.0007	38 ± 4
dev	937 ± 4	0 ± 0	0.001 ± 0.001	38 ± 4

Full metrics [sampling interval: 1]

Full metrics [sampling interval: 1]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	51000 ± 1000	1 ± 0	2.3e-05 ± 8e-06	29.9 ± 0.7
3.5.0	51000 ± 1000	1 ± 0	2.4e-05 ± 7e-06	29.9 ± 0.7
dev	51000 ± 900	1 ± 0	2.3e-05 ± 9e-06	29.8 ± 0.6

Full metrics [sampling interval: 10]

Full metrics [sampling interval: 10]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	51800 ± 600	1 ± 0	3e-05 ± 1e-05	29.5 ± 0.5
3.5.0	51000 ± 2000	1 ± 0	2e-05 ± 1e-05	30 ± 1
dev	50000 ± 2000	1 ± 0	2.3e-05 ± 8e-06	30 ± 1

Full metrics [sampling interval: 100]

Full metrics [sampling interval: 100]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	9800 ± 200	0.0019 ± 0.0003	7e-05 ± 6e-05	34.1 ± 0.7
3.5.0	9800 ± 200	0.0018 ± 0.0002	6e-05 ± 3e-05	33.9 ± 0.6
dev	9800 ± 200	0.002 ± 0.002	4e-05 ± 4e-05	34 ± 1

Full metrics [sampling interval: 1000]

Full metrics [sampling interval: 1000]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	1860 ± 20	0.0003 ± 0.0003	6e-05 ± 9e-05	39 ± 1
3.5.0	1860 ± 20	0.0003 ± 0.0002	4e-05 ± 8e-05	39.3 ± 0.9
dev	1870 ± 20	0.0002 ± 0.0003	6e-05 ± 9e-05	39 ± 2

Multiprocess wall time [sampling interval: 1]

Multiprocess wall time [sampling interval: 1]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	2500 ± 300	1 ± 0	0.00019 ± 0.0001	260 ± 20
3.5.0	3100 ± 200	1 ± 0	0.0003 ± 0.0003	310 ± 20
dev	3100 ± 100	1 ± 0	0.00015 ± 4e-05	310 ± 10

Multiprocess wall time [sampling interval: 10]

Multiprocess wall time [sampling interval: 10]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	2500 ± 200	1 ± 0	0.0003 ± 0.0003	257 ± 9
3.5.0	3100 ± 200	1 ± 0	0.0002 ± 0.0002	310 ± 20
dev	2900 ± 200	1 ± 0	0.00014 ± 5e-05	320 ± 20

Multiprocess wall time [sampling interval: 100]

Multiprocess wall time [sampling interval: 100]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	2300 ± 200	0.03 ± 0.02	0.00012 ± 5e-05	270 ± 20
3.5.0	2900 ± 200	0.05 ± 0.02	8e-05 ± 4e-05	330 ± 20
dev	2900 ± 100	0.06 ± 0.01	5e-05 ± 3e-05	330 ± 20

Multiprocess wall time [sampling interval: 1000]

Multiprocess wall time [sampling interval: 1000]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	2100 ± 200	0.0012 ± 0.0006	3e-05 ± 3e-05	47 ± 4
3.5.0	2800 ± 200	0.013 ± 0.002	3e-05 ± 2e-05	100 ± 10
dev	2700 ± 400	0.011 ± 0.005	1e-05 ± 2e-05	90 ± 20