[llvm] 8c2c972 - [CSSPGO][llvm-profgen] Ignore LBR records after interrupt transition
Hongtao Yu via llvm-commits
llvm-commits at lists.llvm.org
Fri Jun 18 12:14:19 PDT 2021
Author: Hongtao Yu
Date: 2021-06-18T12:13:53-07:00
New Revision: 8c2c97287eacda1ed9cbee893054d868e3b990c5
URL: https://github.com/llvm/llvm-project/commit/8c2c97287eacda1ed9cbee893054d868e3b990c5
DIFF: https://github.com/llvm/llvm-project/commit/8c2c97287eacda1ed9cbee893054d868e3b990c5.diff
LOG: [CSSPGO][llvm-profgen] Ignore LBR records after interrupt transition
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
Added:
llvm/test/tools/llvm-profgen/Inputs/cs-interrupt.perfscript
llvm/test/tools/llvm-profgen/cs-interrupt.test
Modified:
llvm/tools/llvm-profgen/PerfReader.cpp
Removed:
################################################################################
diff --git a/llvm/test/tools/llvm-profgen/Inputs/cs-interrupt.perfscript b/llvm/test/tools/llvm-profgen/Inputs/cs-interrupt.perfscript
new file mode 100644
index 0000000000000..bd782aa9b1851
--- /dev/null
+++ b/llvm/test/tools/llvm-profgen/Inputs/cs-interrupt.perfscript
@@ -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.
diff --git a/llvm/test/tools/llvm-profgen/cs-interrupt.test b/llvm/test/tools/llvm-profgen/cs-interrupt.test
new file mode 100644
index 0000000000000..79b359f085b14
--- /dev/null
+++ b/llvm/test/tools/llvm-profgen/cs-interrupt.test
@@ -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;
+}
diff --git a/llvm/tools/llvm-profgen/PerfReader.cpp b/llvm/tools/llvm-profgen/PerfReader.cpp
index cca1e0324c14d..aaa4a06a2283c 100644
--- a/llvm/tools/llvm-profgen/PerfReader.cpp
+++ b/llvm/tools/llvm-profgen/PerfReader.cpp
@@ -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)
- 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;
+ if (IsExternal)
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
diff erent 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
+ //
diff erent 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));
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