[all-commits] [llvm/llvm-project] 59da1a: [memprof] Speed up caller-callee pair extraction (...

[Kazu Hirata via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 59da1afd2ad74af2a8b8475412353c5d54a7d7f5
      https://github.com/llvm/llvm-project/commit/59da1afd2ad74af2a8b8475412353c5d54a7d7f5
  Author: Kazu Hirata <kazu at google.com>
  Date:   2024-11-14 (Thu, 14 Nov 2024)

  Changed paths:
    M llvm/include/llvm/ProfileData/InstrProfReader.h
    M llvm/lib/ProfileData/InstrProfReader.cpp
    M llvm/lib/ProfileData/InstrProfWriter.cpp

  Log Message:
  -----------
  [memprof] Speed up caller-callee pair extraction (#116184)

We know that the MemProf profile has a lot of duplicate call stacks.
Extracting caller-callee pairs from a call stack we've seen before is
a wasteful effort.

This patch makes the extraction more efficient by first coming up with
a work list of linear call stack IDs -- the set of starting positions
in the radix tree array -- and then extract caller-callee pairs from
each call stack in the work list.

We implement the work list as a bit vector because we expect the work
list to be dense in the range [0, RadixTreeSize).  Also, we want the
set insertion to be cheap.

Without this patch, it takes 25 seconds to extract caller-callee pairs
from a large MemProf profile.  This patch shortenes that down to 4
seconds.



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