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[CSSPGO][llvm-profgen] Ignore LBR records after interrupt transition

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If we have seen an inwards transition from external code to internal code, but not a following outwards transition, the inwards transition is likely due to interrupt which is usually unpaired. Ignore current  and subsequent entries since they are likely from an unrelated pre-interrupt context.

LBR records from different interrupt context are unrelated and they should not be mixed together. Currenlty the OS does this for task-scheduling interrupt but not for all interrupts.

Reviewed By: wenlei, wlei

Differential Revision: https://reviews.llvm.org/D104276
This commit is contained in:
Hongtao Yu 2021-06-17 18:15:45 -07:00
parent 7f0aeb0ac8
commit f2d99918a7
3 changed files with 104 additions and 12 deletions
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16
test/tools/llvm-profgen/Inputs/cs-interrupt.perfscript Normal file
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@ -0,0 +1,16 @@
PERF_RECORD_MMAP2 2854748/2854748: [0x400000(0x1000) @ 0 00:1d 123291722 526021]: r-xp /home/noinline-cs-noprobe.perfbin
4005dc
400634
400684
7f68c5788793
0x4005c8/0x4005dc/P/-/-/0 0x40062f/0x4005b0/P/-/-/0 0x400645/0x4005ff/P/-/-/0 0x400637/0x400645/P/-/-/0 0x4005e9/0x400634/P/-/-/0 0x4005d7/0x4005e5/P/-/-/0 0x40062f/0x4005b0/P/-/-/0 0x400645/0x4005ff/P/-/-/0 0x400637/0x400645/P/-/-/0 0x4005e9/0x400634/P/-/-/0 0x4005d7/0x4005e5/P/-/-/0 0x40062f/0x4005b0/P/-/-/0 0x400645/0x4005ff/P/-/-/0 0x400637/0x400645/P/-/-/0 0xffffffff81c009d0/0x400634/P/-/-/0 0x40048a/0x40048e/P/-/-/0
4005dc
400634
400684
7f68c5788793
0x4005c8/0x4005dc/P/-/-/0 0x40062f/0x4005b0/P/-/-/0 0x400645/0x4005ff/P/-/-/0 0x400637/0x400645/P/-/-/0 0x4005e9/0x400634/P/-/-/0 0x4005d7/0x4005e5/P/-/-/0 0x40062f/0x4005b0/P/-/-/0 0x400645/0x4005ff/P/-/-/0 0x400637/0x400645/P/-/-/0 0x4005e9/0x400634/P/-/-/0 0x4005d7/0x4005e5/P/-/-/0 0x400634/0xffffffff81c009d0/P/-/-/0 0x40062f/0x4005b0/P/-/-/0 0x400645/0x4005ff/P/-/-/0 0x400637/0x400645/P/-/-/0 0x40048a/0x40048e/P/-/-/0
// Transition 0xffffffff81c009d0/0x400634 is due to interrupt. Records after it, i.e, 0x40048a/0x40048e, should be ignored to avoid bogus instruction ranges.

56
test/tools/llvm-profgen/cs-interrupt.test Normal file
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@ -0,0 +1,56 @@
; RUN: llvm-profgen --format=text --perfscript=%S/Inputs/cs-interrupt.perfscript --binary=%S/Inputs/noinline-cs-noprobe.perfbin --output=%t --show-unwinder-output --profile-summary-cold-count=0 | FileCheck %s --check-prefix=CHECK-UNWINDER
; RUN: FileCheck %s --input-file %t
; CHECK:[main:1 @ foo]:88:0
; CHECK: 2: 5
; CHECK: 3: 5 bar:5
; CHECK:[main:1 @ foo:3 @ bar]:74:5
; CHECK: 0: 5
; CHECK: 1: 5
; CHECK: 2: 3
; CHECK: 5: 4
; CHECK-UNWINDER: Binary(noinline-cs-noprobe.perfbin)'s Range Counter:
; CHECK-UNWINDER: main:1 @ foo
; CHECK-UNWINDER: (5ff, 62f): 5
; CHECK-UNWINDER: (634, 637): 4
; CHECK-UNWINDER: (645, 645): 5
; CHECK-UNWINDER: main:1 @ foo:3 @ bar
; CHECK-UNWINDER: (5b0, 5c8): 2
; CHECK-UNWINDER: (5b0, 5d7): 3
; CHECK-UNWINDER: (5e5, 5e9): 4
; CHECK-UNWINDER: Binary(noinline-cs-noprobe.perfbin)'s Branch Counter:
; CHECK-UNWINDER: main:1 @ foo
; CHECK-UNWINDER: (62f, 5b0): 5
; CHECK-UNWINDER: (637, 645): 5
; CHECK-UNWINDER: (645, 5ff): 5
; CHECK-UNWINDER: main:1 @ foo:3 @ bar
; CHECK-UNWINDER: (5c8, 5dc): 2
; CHECK-UNWINDER: (5d7, 5e5): 4
; CHECK-UNWINDER: (5e9, 634): 4
; original code:
; clang -O0 -g test.c -o a.out
#include <stdio.h>
int bar(int x, int y) {
if (x % 3) {
return x - y;
}
return x + y;
}
void foo() {
int s, i = 0;
while (i++ < 4000 * 4000)
if (i % 91) s = bar(i, s); else s += 30;
printf("sum is %d\n", s);
}
int main() {
foo();
return 0;
}

44
tools/llvm-profgen/PerfReader.cpp
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@ -444,27 +444,47 @@ bool PerfReader::extractLBRStack(TraceStream &TraceIt,
bool SrcIsInternal = Binary->addressIsCode(Src);
bool DstIsInternal = Binary->addressIsCode(Dst);
bool IsExternal = !SrcIsInternal && !DstIsInternal;
bool IsIncoming = !SrcIsInternal && DstIsInternal;
bool IsOutgoing = SrcIsInternal && !DstIsInternal;
bool IsArtificial = false;
// Ignore branches outside the current binary.
if (!SrcIsInternal && !DstIsInternal)
if (IsExternal)
continue;
if (!SrcIsInternal && DstIsInternal) {
// For transition from external code (such as dynamic libraries) to
// the current binary, keep track of the branch target which will be
// grouped with the Source of the last transition from the current
// binary.
PrevTrDst = Dst;
continue;
}
if (SrcIsInternal && !DstIsInternal) {
if (IsOutgoing) {
if (!PrevTrDst) {
// This is unpaired outgoing jump which is likely due to interrupt or
// incomplete LBR trace. Ignore current and subsequent entries since
// they are likely in different contexts.
break;
}
// For transition to external code, group the Source with the next
// availabe transition target.
if (!PrevTrDst)
continue;
Dst = PrevTrDst;
PrevTrDst = 0;
IsArtificial = true;
} else {
if (PrevTrDst) {
// If we have seen an incoming transition from external code to internal
// code, but not a following outgoing transition, the incoming
// transition is likely due to interrupt which is usually unpaired.
// Ignore current and subsequent entries since they are likely in
// different contexts.
break;
}
if (IsIncoming) {
// For transition from external code (such as dynamic libraries) to
// the current binary, keep track of the branch target which will be
// grouped with the Source of the last transition from the current
// binary.
PrevTrDst = Dst;
continue;
}
}
// TODO: filter out buggy duplicate branches on Skylake
LBRStack.emplace_back(LBREntry(Src, Dst, IsArtificial));