why WithPartialCompilationAndDisabledBaselineProfile is the best result in StartupBenchmark

[hxu-wish]

In startupbenchmark file, we have four ways to test the startup performance

1. WithoutPreCompilation
2. PrecompiledWithBaselineProfile
3. WithPartialCompilationAndDisabledBaselineProfile
4. FullyPrecompiled

Then I run and found out that 3 is the best way for performance.

Why it happen? It did not use baseline profile at all. Is there anything wrong?

Relevant logcat output

StartupBenchmark_startupWithoutPreCompilation timeToInitialDisplayMs min 1,279.5, median 1,312.9, max 1,459.9 Traces: Iteration 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
StartupBenchmark_startupPrecompiledWithBaselineProfile
timeToInitialDisplayMs min 862.2, median 889.2, max 1,103,080.4 improve 34%
Traces: Iteration 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
StartupBenchmark_startupWithPartialCompilationAndDisabledBaselineProfile
timeToInitialDisplayMs min 735.0, median 757.1, max 786.2 improve 42%
Traces: Iteration 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
StartupBenchmark_startupFullyPrecompiled
timeToInitialDisplayMs min 855.4, median 886.7, max 1,074.9 improve 32%
Traces: Iteration 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

[hxu-wish]

Here is some reference

https://developer.android.com/reference/androidx/benchmark/macro/CompilationMode

Partial - the default configuration of Partial will partially pre-compile your application, if a Baseline Profile is included in your app. This represents the most realistic fresh-install experience on an end-user's device. You can additionally or instead use Partial.warmupIterations to use Profile Guided Optimization, using the benchmark content to guide pre-compilation. This can mimic an application's performance after background dexopt has partially compiled the app during device idle time, after the app has been used (generally after a day or more of usage after update/install).

startupWithPartialCompilationAndDisabledBaselineProfile don't equal to not use pre-compile. It is more like a combination between AOT and JIT. If startupWithPartialCompilationAndDisabledBaselineProfile have better performance than StartupBenchmark_startupPrecompiledWithBaselineProfile. I believe baselineprofile is not that good enough.

Here bring another question, how to get a good baseline profile file? Looks it is better not to do anything. No need to use baseline profile. startupWithPartialCompilationAndDisabledBaselineProfile has the best performance to startupbenchmark.