Aggressive optimization and inlining foor PooledList.Span

Is your feature request related to a problem? Please describe. Next method is kind of slow in Unity runtime (not sure about Core):

public Span<T> Span => _items.AsSpan(0, _size);

Describe the solution you’d like Mark this method as aggressive optimization and inlining.

Describe alternatives you’ve considered Provide unsafe access to writable array as ReadOnlyProperty.

Additional context We get data from Span by ref.

I know Core 3 optimized Span, but there are issues to measure that because of BDN-JIT instability. Same time Unity is involved into .NET Ecosystem and hopefully will optimize Span in some time (because people will use .NET Standard with Spans and Unity stated it is 2.0 and will be 2.1)

[jtmueller]

Sorry for the delayed response. Here’s what I’m currently seeing without your suggested optimization, run from the “core3” branch:

Method	Runtime	N	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
PooledSpan	.NET 4.8	1000	16.09 us	0.066 us	0.062 us	-	-	-	-
PooledIndex	.NET 4.8	1000	17.42 us	0.093 us	0.087 us	-	-	-	-
PooledSpan	.NET Core 3.0	1000	11.34 us	0.108 us	0.101 us	-	-	-	-
PooledIndex	.NET Core 3.0	1000	17.44 us	0.107 us	0.100 us	-	-	-	-
PooledSpan	.NET 4.8	10000	16.08 us	0.120 us	0.112 us	-	-	-	-
PooledIndex	.NET 4.8	10000	17.43 us	0.074 us	0.069 us	-	-	-	-
PooledSpan	.NET Core 3.0	10000	11.25 us	0.044 us	0.039 us	-	-	-	-
PooledIndex	.NET Core 3.0	10000	17.38 us	0.108 us	0.101 us	-	-	-	-
PooledSpan	.NET 4.8	100000	16.03 us	0.066 us	0.062 us	-	-	-	-
PooledIndex	.NET 4.8	100000	17.41 us	0.110 us	0.103 us	-	-	-	-
PooledSpan	.NET Core 3.0	100000	11.23 us	0.046 us	0.043 us	-	-	-	-
PooledIndex	.NET Core 3.0	100000	17.47 us	0.088 us	0.082 us	-	-	-	-

And here’s what I’m seeing with AggressiveInlining applied to the “Span” property getter. There doesn’t seem to be a significant change by doing this. Perhaps I’m misunderstanding what you’re proposing?

Method	Runtime	N	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
PooledSpan	.NET 4.8	1000	16.28 us	0.327 us	0.480 us	-	-	-	-
PooledIndex	.NET 4.8	1000	17.41 us	0.138 us	0.130 us	-	-	-	-
PooledSpan	.NET Core 3.0	1000	11.26 us	0.067 us	0.059 us	-	-	-	-
PooledIndex	.NET Core 3.0	1000	17.35 us	0.090 us	0.084 us	-	-	-	-
PooledSpan	.NET 4.8	10000	16.15 us	0.182 us	0.152 us	-	-	-	-
PooledIndex	.NET 4.8	10000	17.41 us	0.164 us	0.145 us	-	-	-	-
PooledSpan	.NET Core 3.0	10000	11.25 us	0.075 us	0.070 us	-	-	-	-
PooledIndex	.NET Core 3.0	10000	17.38 us	0.111 us	0.104 us	-	-	-	-
PooledSpan	.NET 4.8	100000	16.13 us	0.074 us	0.062 us	-	-	-	-
PooledIndex	.NET 4.8	100000	17.37 us	0.111 us	0.103 us	-	-	-	-
PooledSpan	.NET Core 3.0	100000	11.27 us	0.074 us	0.066 us	-	-	-	-
PooledIndex	.NET Core 3.0	100000	17.38 us	0.079 us	0.070 us	-	-	-	-

public Span<T> Span
{
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
        return _items.AsSpan(0, _size);
    }
}

[dzmitry-lahoda]

MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization ? It may not help either. But at least, in Unity IL2CPP both span and index were slow, so people put items array as public. So if nothing changes, may be leave both optimization in place so that possible other runtimes will have more chances to hit the optimization? Just as idea, but anyway - may close the issue. Thanks