Performance regression: 6x slower array allocation on Alpine

[adamsitnik]

From the data that I got from @danmosemsft which was collected by running dotnet/performance microbenchmarks on alpine 3.11 via WSL2, it looks like allocating arrays of both value and reference types became 6 times slower compared to 3.1.

Initially, I thought that it was just an outlier, but I can see the same pattern for other collections that internally use arrays (queue, list, stack etc). The regression is specific to alpine. Ubuntu 18.04 (with and without WSL2) is fine.

@jkotas @janvorli who would be the best person to investigate that?

Repro

git clone https://github.com/dotnet/performance.git
python3 ./performance/scripts/benchmarks_ci.py -f netcoreapp3.1 netcoreapp5.0 --filter 'System.Collections.CtorGivenSize<Int32>.Array'

System.Collections.CtorGivenSize.Array(Size: 512)

Conclusion	Base	Diff	Base/Diff	Modality	Operating System	Bit	Processor Name	Base Runtime	Diff Runtime
Same	181.79	183.96	0.99		Windows 10.0.18363.1016	Arm	Microsoft SQ1 3.0 GHz	.NET Core 3.1.6	5.0.100-rc.1.20413.9
Same	92.89	94.47	0.98		Windows 10.0.18363.959	X64	Intel Xeon CPU E5-1650 v4 3.60GHz	.NET Core 3.1.6	5.0.100-rc.1.20404.3
Same	96.05	94.36	1.02		Windows 10.0.18363.959	X64	Intel Xeon CPU E5-1650 v4 3.60GHz	.NET Core 3.1.6	5.0.100-rc.1.20418.3
Same	114.74	111.94	1.03		Windows 10.0.19041.450	X64	Intel Core i7-5557U CPU 3.10GHz (Broadwell)	.NET Core 3.1.6	5.0.100-rc.1.20413.9
Same	80.49	79.98	1.01		Windows 10.0.19041.450	X64	Intel Core i7-6700 CPU 3.40GHz (Skylake)	.NET Core 3.1.6	5.0.100-rc.1.20419.9
Same	67.30	67.66	0.99	bimodal	Windows 10.0.19042	X64	Intel Core i7-7700 CPU 3.60GHz (Kaby Lake)	.NET Core 3.1.6	5.0.100-rc.1.20418.3
Same	86.10	79.17	1.09	bimodal	Windows 10.0.19041.450	X64	Intel Core i7-8650U CPU 1.90GHz (Kaby Lake R)	.NET Core 3.1.6	5.0.100-rc.1.20419.14
Same	97.50	98.77	0.99		Windows 10.0.18363.959	X86	Intel Xeon CPU E5-1650 v4 3.60GHz	.NET Core 3.1.6	5.0.100-rc.1.20420.14
Slower	127.02	150.46	0.84	bimodal	Windows 10.0.19041.450	X86	Intel Core i7-5557U CPU 3.10GHz (Broadwell)	.NET Core 3.1.6	5.0.100-rc.1.20419.5
Slower	193.61	287.83	0.67	bimodal	ubuntu 18.04	Arm64	Unknown processor	.NET Core 3.1.6	6.0.100-alpha.1.20421.6
Same	99.85	103.42	0.97		ubuntu 18.04	X64	Intel Xeon CPU E5-1650 v4 3.60GHz	.NET Core 3.1.6	5.0.100-rc.1.20403.23
Slower	138.73	151.37	0.92		macOS Mojave 10.14.5	X64	Intel Core i7-5557U CPU 3.10GHz (Broadwell)	.NET Core 3.1.6	5.0.100-rc.1.20404.2
Slower	72.85	515.56	0.14		alpine 3.11	X64	Intel Core i7-7700 CPU 3.60GHz (Kaby Lake)	.NET Core 3.1.6	6.0.100-alpha.1.20421.6
Slower	78.85	90.76	0.87		ubuntu 18.04	X64	Intel Core i7-7700 CPU 3.60GHz (Kaby Lake)	.NET Core 3.1.6	5.0.100-rc.1.20418.3

[danmoseley]

@billwert

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[jkotas]

These tests are measuring raw GC allocation speed. This is GC performance regression.

@mangod9 Could you please find somebody to investigate this?

[mangod9]

Ok will have someone take a look. @adamsitnik , Is the regression specifically with Alpine on WSL2, or Alpine in general?

[adamsitnik]

Is the regression specifically with Alpine on WSL2, or Alpine in general?

mangod9 The benchmarks were executed with Alpine on WSL2, I don't have "Alpine only" results to be able to answer. FWIW the Ubuntu on WSL2 results are fine so it might be a general Alpine problem

[jkotas]

It repros without WSL2 too.

The problem is that the GC is running like 100x more often than it should. It is likely problem in the budget computation. One of the places to check is PAL_GetLogicalProcessorCacheSizeFromOS.

[mangod9]

ok thanks for the context. We will look if there is any Alpine specific behavior which is leading to this.