[Impeller] dont allocate capture strings in release mode. #48760
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gaaclarke
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gaaclarke
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You know what is happening, there must be a place where someone is calling these functions with a char* so even though it is a const std::string& it will create a std::string which copies the value so that it can pass a reference to that. std::string_view will never copy. You can use a std::string_view here. It's probably faster than const std::string_view& considering it's so small and avoids another level of indirection.
Test exempt: No logical change, the effects will be measured in a benchmark.
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test-exempt: code refactor with no semantic change (Do we have a benchmark that would catch a regression here though?) |
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| FML_DCHECK(element_ != nullptr); \ | ||
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| std::string label_clone = std::string(label); \ |
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Can we not push the use of string_view further into the stack so callers don't have to make copies?
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We could. I decided to stop here because the rest of this is debug only is compiled out for profile/release modes.
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| auto new_capture = Capture(label); | ||
| std::string label_copy = std::string(label); |
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The benchmark I use to measure these smaller optimziations is https://flutter-flutter-perf.skia.org/e/?queries=sub_result%3D90th_percentile_frame_rasterizer_time_millis%26sub_result%3Daverage_frame_rasterizer_time_millis%26test%3Dcomplex_layout_scroll_perf_ios__timeline_summary&selected=commit%3D38127%26name%3D%2Carch%3Dintel%2Cbranch%3Dmaster%2Cconfig%3Ddefault%2Cdevice_type%3DiPhone_11%2Cdevice_version%3Dnone%2Chost_type%3Dmac%2Csub_result%3Daverage_frame_rasterizer_time_millis%2Ctest%3Dcomplex_layout_scroll_perf_ios__timeline_summary%2C Its probably too much noise for us to identify individual regressions, but by landing these sorts of improvements we've been able to gradually drive this down over time. |
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…139831) flutter/engine@7dc51b8...e9cb19f 2023-12-08 [email protected] [Impeller] dont allocate capture strings in release mode. (flutter/engine#48760) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-engine-flutter-autoroll Please CC [email protected],[email protected],[email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
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I'm not exactly sure why, but this seems to stop the allocation of capture labels in release mode.
Fixes flutter/flutter#138908