PatriosTheGreat requested review of this revision. PatriosTheGreat added a comment.
Thanks for feedback. I made a small sample: https://pastebin.com/F8nde1zi Compile command: clang++ -O0 -g -pthread sample.cpp LLDB command: breakpoint set -f sample.cpp -l 24 --condition 'i == 100' This break should not be hit due to the condition. I got followed results for local and remote run: LLDB 11: Local: Time difference = 10 330 [ms] Remote: Time difference = 189 707 [ms] Patched (turned off select of the most relevant frame for threads which were stopped without a reason): Local: Time difference = 7 865 [ms] Remote: Time difference = 13 630 [ms] Looks like there is a performance improvement even with local run, but with remote run it becomes much more significant. In D103271#2785450 <https://reviews.llvm.org/D103271#2785450>, @jingham wrote: > It is incorrect to say that SelectMostRelevantFrame is only relevant for > asserts. The FrameRecognizer is a generic mechanism, and you have no a > priori way to know what kinds of thread stops it wants to operate on. So > this patch is not correct. > > Other than calling the Frame Recognizers, SelectMostRelevantFrame does NOT > trigger a stack walk itself. > > So if there is a frame recognizer that is doing a frame walk on threads that > aren't relevant to it, then changing the frame recognizer to check that the > stop reason of its thread makes sense before doing any work seems a better > solution to your problem. From performance analyzer I see that SelectMostRelevantFrame calls StackFrameList::GetFrameAtIndex -> StackFrameList::GetFramesUpTo -> UnwindLLDB::DoGetFrameInfoAtIndex -> UnwindLLDB::AddFirstFrame UnwindLLDB::AddFirstFrame calls two expensive methods: UnwindLLDB::UpdateUnwindPlanForFirstFrameIfInvalid (takes around 2/3 of execution time) and UnwindLLDB::RegisterContextUnwind (takes around 1/3 of execution time) Does frame recognition relevant for threads which were stopped without any reason? May I filter this logic like this: lldb::StopReason stop_reason = GetStopReason(); if (stop_reason != lldb::StopReason::eStopReasonNone) SelectMostRelevantFrame(); If this is also an incorrect solution may we somehow select most relevant frame without calling of UnwindLLDB::DoGetFrameInfoAtIndex? Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D103271/new/ https://reviews.llvm.org/D103271 _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
