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[StaleProfileMatching] Use only profile anchor size for similarity calculation #126783

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Merged
merged 2 commits into from
Feb 13, 2025
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[StaleProfileMatching] Use only profile anchor size for similarity calculation #126783

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[StaleProfileMatching] Use only profile anchor size for similarity ca…
wlei-llvm Feb 11, 2025
dce2f9d
chang back similarity-threshold 80(will tune separately)
wlei-llvm Feb 13, 2025
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7 changes: 3 additions & 4 deletions llvm/lib/Transforms/IPO/SampleProfileMatcher.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ using namespace sampleprof;
#define DEBUG_TYPE "sample-profile-matcher"

static cl::opt<unsigned> FuncProfileSimilarityThreshold(
"func-profile-similarity-threshold", cl::Hidden, cl::init(80),
"func-profile-similarity-threshold", cl::Hidden, cl::init(70),
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any explanation for the change in threshold? in addition to the change in how it's calculated

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This is just from my observation, may not be accurate. I observed that there were many false negatives(we missed the good match). Recalling that it's under the LCS frame, the matching scope is narrowed, it's very likely to have a good match. So I feel overall threshold is a bit too high, so try to lower it a bit.

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Is 10% drop meaningful, is 70% final? If so, it's okay to include it here, otherwise the tuning can be done separately.

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Is 10% drop meaningful, is 70% final? If so, it's okay to include it here, otherwise the tuning can be done separately.

I see, sounds good to tune separately.

cl::desc("Consider a profile matches a function if the similarity of their "
"callee sequences is above the specified percentile."));

Expand Down Expand Up @@ -790,9 +790,8 @@ bool SampleProfileMatcher::functionMatchesProfileHelper(
longestCommonSequence(FilteredIRAnchorsList, FilteredProfileAnchorList,
false /* Match unused functions */);

Similarity =
static_cast<float>(MatchedAnchors.size()) * 2 /
(FilteredIRAnchorsList.size() + FilteredProfileAnchorList.size());
Similarity = static_cast<float>(MatchedAnchors.size()) /
FilteredProfileAnchorList.size();

LLVM_DEBUG(dbgs() << "The similarity between " << IRFunc.getName()
<< "(IR) and " << ProfFunc << "(profile) is "
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2 changes: 1 addition & 1 deletion llvm/test/Transforms/SampleProfile/pseudo-probe-stale-profile-renaming.ll
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Expand Up @@ -8,7 +8,7 @@
; CHECK: Function new_foo is not in profile or profile symbol list.

; CHECK: Run stale profile matching for main
; CHECK: The similarity between new_foo(IR) and foo(profile) is 0.86
; CHECK: The similarity between new_foo(IR) and foo(profile) is 0.75
; CHECK: Function:new_foo matches profile:foo
; CHECK: Run stale profile matching for cold_func
; CHECK: The checksums for new_block_only(IR) and block_only(Profile) match.
Expand Down