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Use profile summary to disable peeling for huge working sets

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Summary:
Detect when the working set size of a profiled application is huge,
by comparing the number of counts required to reach the hot percentile
in the profile summary to a large threshold*.

When the working set size is determined to be huge, disable peeling
to avoid bloating the working set further.

*Note that the selected threshold (15K) is significantly larger than the
largest working set value in SPEC cpu2006 (which is gcc at around 11K).

Reviewers: davidxl

Subscribers: mehdi_amini, mzolotukhin, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D36288

llvm-svn: 310005
This commit is contained in:
Teresa Johnson 2017-08-03 23:42:58 +00:00
parent 4c3807ce80
commit cde6934bb7
6 changed files with 86 additions and 31 deletions
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6
include/llvm/Analysis/ProfileSummaryInfo.h
View File

@ -49,6 +49,10 @@ private:
void computeThresholds();
// Count thresholds to answer isHotCount and isColdCount queries.
Optional<uint64_t> HotCountThreshold, ColdCountThreshold;
// True if the working set size of the code is considered huge,
// because the number of profile counts required to reach the hot
// percentile is above a huge threshold.
Optional<bool> HasHugeWorkingSetSize;
public:
ProfileSummaryInfo(Module &M) : M(M) {}
@ -84,6 +88,8 @@ public:
/// Returns the profile count for \p CallInst.
Optional<uint64_t> getProfileCount(const Instruction *CallInst,
BlockFrequencyInfo *BFI);
/// Returns true if the working set size of the code is considered huge.
bool hasHugeWorkingSetSize();
/// \brief Returns true if \p F has hot function entry.
bool isFunctionEntryHot(const Function *F);
/// Returns true if \p F has hot function entry or hot call edge.

32
lib/Analysis/ProfileSummaryInfo.cpp
View File

@ -44,10 +44,16 @@ static cl::opt<bool> AccurateSampleProfile(
cl::desc("If the sample profile is accurate, we will mark all un-sampled "
"callsite as cold. Otherwise, treat un-sampled callsites as if "
"we have no profile."));
static cl::opt<unsigned> ProfileSummaryHugeWorkingSetSizeThreshold(
"profile-summary-huge-working-set-size-threshold", cl::Hidden,
cl::init(15000), cl::ZeroOrMore,
cl::desc("The code working set size is considered huge if the number of"
" blocks required to reach the -profile-summary-cutoff-hot"
" percentile exceeds this count."));
// Find the minimum count to reach a desired percentile of counts.
static uint64_t getMinCountForPercentile(SummaryEntryVector &DS,
uint64_t Percentile) {
// Find the summary entry for a desired percentile of counts.
static const ProfileSummaryEntry &getEntryForPercentile(SummaryEntryVector &DS,
uint64_t Percentile) {
auto Compare = [](const ProfileSummaryEntry &Entry, uint64_t Percentile) {
return Entry.Cutoff < Percentile;
};
@ -56,7 +62,7 @@ static uint64_t getMinCountForPercentile(SummaryEntryVector &DS,
// detailed summary.
if (It == DS.end())
report_fatal_error("Desired percentile exceeds the maximum cutoff");
return It->MinCount;
return *It;
}
// The profile summary metadata may be attached either by the frontend or by
@ -169,10 +175,20 @@ void ProfileSummaryInfo::computeThresholds() {
if (!computeSummary())
return;
auto &DetailedSummary = Summary->getDetailedSummary();
HotCountThreshold =
getMinCountForPercentile(DetailedSummary, ProfileSummaryCutoffHot);
ColdCountThreshold =
getMinCountForPercentile(DetailedSummary, ProfileSummaryCutoffCold);
auto &HotEntry =
getEntryForPercentile(DetailedSummary, ProfileSummaryCutoffHot);
HotCountThreshold = HotEntry.MinCount;
auto &ColdEntry =
getEntryForPercentile(DetailedSummary, ProfileSummaryCutoffCold);
ColdCountThreshold = ColdEntry.MinCount;
HasHugeWorkingSetSize =
HotEntry.NumCounts > ProfileSummaryHugeWorkingSetSizeThreshold;
}
bool ProfileSummaryInfo::hasHugeWorkingSetSize() {
if (!HasHugeWorkingSetSize)
computeThresholds();
return HasHugeWorkingSetSize && HasHugeWorkingSetSize.getValue();
}
bool ProfileSummaryInfo::isHotCount(uint64_t C) {

24
lib/Transforms/Scalar/LoopUnrollPass.cpp
View File

@ -21,6 +21,7 @@
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/LoopUnrollAnalyzer.h"
#include "llvm/Analysis/OptimizationDiagnosticInfo.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/IR/DataLayout.h"
@ -1252,6 +1253,11 @@ PreservedAnalyses LoopUnrollPass::run(Function &F,
auto &AC = AM.getResult<AssumptionAnalysis>(F);
auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
const ModuleAnalysisManager &MAM =
AM.getResult<ModuleAnalysisManagerFunctionProxy>(F).getManager();
ProfileSummaryInfo *PSI =
MAM.getCachedResult<ProfileSummaryAnalysis>(*F.getParent());
bool Changed = false;
// The unroller requires loops to be in simplified form, and also needs LCSSA.
@ -1280,12 +1286,18 @@ PreservedAnalyses LoopUnrollPass::run(Function &F,
// states we support: partial and full (or "simple") unrolling. However, to
// enable these things we actually pass "None" in for the optional to avoid
// providing an explicit choice.
Optional<bool> AllowPartialParam, RuntimeParam, UpperBoundParam;
bool CurChanged = tryToUnrollLoop(
&L, DT, &LI, SE, TTI, AC, ORE,
/*PreserveLCSSA*/ true, OptLevel, /*Count*/ None,
/*Threshold*/ None, AllowPartialParam, RuntimeParam, UpperBoundParam,
/*AllowPeeling*/ None);
Optional<bool> AllowPartialParam, RuntimeParam, UpperBoundParam,
AllowPeeling;
// Check if the profile summary indicates that the profiled application
// has a huge working set size, in which case we disable peeling to avoid
// bloating it further.
if (PSI && PSI->hasHugeWorkingSetSize())
AllowPeeling = false;
bool CurChanged =
tryToUnrollLoop(&L, DT, &LI, SE, TTI, AC, ORE,
/*PreserveLCSSA*/ true, OptLevel, /*Count*/ None,
/*Threshold*/ None, AllowPartialParam, RuntimeParam,
UpperBoundParam, AllowPeeling);
Changed |= CurChanged;
// The parent must not be damaged by unrolling!

1
test/Other/new-pm-defaults.ll
View File

@ -198,6 +198,7 @@
; CHECK-O-NEXT: Running pass: SimplifyCFGPass
; CHECK-O-NEXT: Running pass: InstCombinePass
; CHECK-O-NEXT: Running pass: LoopUnrollPass
; CHECK-O-NEXT: Running analysis: OuterAnalysisManagerProxy
; CHECK-O-NEXT: Running pass: InstCombinePass
; CHECK-O-NEXT: Running pass: RequireAnalysisPass<{{.*}}OptimizationRemarkEmitterAnalysis
; CHECK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LICMPass

1
test/Other/new-pm-thinlto-defaults.ll
View File

@ -185,6 +185,7 @@
; CHECK-POSTLINK-O-NEXT: Running pass: SimplifyCFGPass
; CHECK-POSTLINK-O-NEXT: Running pass: InstCombinePass
; CHECK-POSTLINK-O-NEXT: Running pass: LoopUnrollPass
; CHECK-POSTLINK-O-NEXT: Running analysis: OuterAnalysisManagerProxy
; CHECK-POSTLINK-O-NEXT: Running pass: InstCombinePass
; CHECK-POSTLINK-O-NEXT: Running pass: RequireAnalysisPass<{{.*}}OptimizationRemarkEmitterAnalysis
; CHECK-POSTLINK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LICMPass

53
test/Transforms/LoopUnroll/peel-loop-pgo.ll
View File

@ -1,5 +1,8 @@
; RUN: opt < %s -S -debug-only=loop-unroll -loop-unroll 2>&1 | FileCheck %s
; RUN: opt < %s -S -debug-only=loop-unroll -passes='require<opt-remark-emit>,unroll' 2>&1 | FileCheck %s
; RUN: opt < %s -S -debug-only=loop-unroll -passes='require<profile-summary>,function(require<opt-remark-emit>,unroll)' 2>&1 | FileCheck %s
; Confirm that peeling is disabled if the number of counts required to reach
; the hot percentile is above the threshold.
; RUN: opt < %s -S -profile-summary-huge-working-set-size-threshold=9 -debug-only=loop-unroll -passes='require<profile-summary>,function(require<opt-remark-emit>,unroll)' 2>&1 | FileCheck %s --check-prefix=NOPEEL
; REQUIRES: asserts
; Make sure we use the profile information correctly to peel-off 3 iterations
@ -11,19 +14,19 @@
; CHECK-NOT: PEELING
; Confirm that no peeling occurs when we are performing full unrolling.
; RUN: opt < %s -S -debug-only=loop-unroll -passes='require<opt-remark-emit>,loop(unroll-full)' 2>&1 | FileCheck %s --check-prefix=FULLUNROLL
; FULLUNROLL-NOT: PEELING
; RUN: opt < %s -S -debug-only=loop-unroll -passes='require<opt-remark-emit>,loop(unroll-full)' 2>&1 | FileCheck %s --check-prefix=NOPEEL
; NOPEEL-NOT: PEELING
; CHECK-LABEL: @basic
; CHECK: br i1 %{{.*}}, label %[[NEXT0:.*]], label %for.cond.for.end_crit_edge, !prof !1
; CHECK: br i1 %{{.*}}, label %[[NEXT0:.*]], label %for.cond.for.end_crit_edge, !prof !15
; CHECK: [[NEXT0]]:
; CHECK: br i1 %{{.*}}, label %[[NEXT1:.*]], label %for.cond.for.end_crit_edge, !prof !2
; CHECK: br i1 %{{.*}}, label %[[NEXT1:.*]], label %for.cond.for.end_crit_edge, !prof !16
; CHECK: [[NEXT1]]:
; CHECK: br i1 %{{.*}}, label %[[NEXT2:.*]], label %for.cond.for.end_crit_edge, !prof !3
; CHECK: br i1 %{{.*}}, label %[[NEXT2:.*]], label %for.cond.for.end_crit_edge, !prof !17
; CHECK: [[NEXT2]]:
; CHECK: br i1 %{{.*}}, label %for.body, label %{{.*}}, !prof !4
; CHECK: br i1 %{{.*}}, label %for.body, label %{{.*}}, !prof !18
define void @basic(i32* %p, i32 %k) #0 !prof !0 {
define void @basic(i32* %p, i32 %k) #0 !prof !15 {
entry:
%cmp3 = icmp slt i32 0, %k
br i1 %cmp3, label %for.body.lr.ph, label %for.end
@ -38,7 +41,7 @@ for.body: ; preds = %for.body.lr.ph, %fo
store i32 %i.05, i32* %p.addr.04, align 4
%inc = add nsw i32 %i.05, 1
%cmp = icmp slt i32 %inc, %k
br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge, !prof !1
br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge, !prof !16
for.cond.for.end_crit_edge: ; preds = %for.body
br label %for.end
@ -54,7 +57,7 @@ for.end: ; preds = %for.cond.for.end_cr
; CHECK: for.body:
; CHECK-NOT: br
; CHECK: br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge
define void @optsize(i32* %p, i32 %k) #1 !prof !0 {
define void @optsize(i32* %p, i32 %k) #1 !prof !15 {
entry:
%cmp3 = icmp slt i32 0, %k
br i1 %cmp3, label %for.body.lr.ph, label %for.end
@ -69,7 +72,7 @@ for.body: ; preds = %for.body.lr.ph, %fo
store i32 %i.05, i32* %p.addr.04, align 4
%inc = add nsw i32 %i.05, 1
%cmp = icmp slt i32 %inc, %k
br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge, !prof !1
br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge, !prof !16
for.cond.for.end_crit_edge: ; preds = %for.body
br label %for.end
@ -81,11 +84,27 @@ for.end: ; preds = %for.cond.for.end_cr
attributes #0 = { nounwind }
attributes #1 = { nounwind optsize }
!0 = !{!"function_entry_count", i64 1}
!1 = !{!"branch_weights", i32 3001, i32 1001}
!llvm.module.flags = !{!1}
;CHECK: !1 = !{!"branch_weights", i32 900, i32 101}
;CHECK: !2 = !{!"branch_weights", i32 540, i32 360}
;CHECK: !3 = !{!"branch_weights", i32 162, i32 378}
;CHECK: !4 = !{!"branch_weights", i32 1399, i32 162}
!1 = !{i32 1, !"ProfileSummary", !2}
!2 = !{!3, !4, !5, !6, !7, !8, !9, !10}
!3 = !{!"ProfileFormat", !"InstrProf"}
!4 = !{!"TotalCount", i64 10}
!5 = !{!"MaxCount", i64 3}
!6 = !{!"MaxInternalCount", i64 1}
!7 = !{!"MaxFunctionCount", i64 3}
!8 = !{!"NumCounts", i64 2}
!9 = !{!"NumFunctions", i64 2}
!10 = !{!"DetailedSummary", !11}
!11 = !{!12, !13, !14}
!12 = !{i32 10000, i64 3, i32 2}
!13 = !{i32 999000, i64 1, i32 10}
!14 = !{i32 999999, i64 1, i32 10}
!15 = !{!"function_entry_count", i64 1}
!16 = !{!"branch_weights", i32 3001, i32 1001}
;CHECK: !15 = !{!"branch_weights", i32 900, i32 101}
;CHECK: !16 = !{!"branch_weights", i32 540, i32 360}
;CHECK: !17 = !{!"branch_weights", i32 162, i32 378}
;CHECK: !18 = !{!"branch_weights", i32 1399, i32 162}