[llvm] 7fb4001 - [SampleFDO] Add a cutoff flag to control how many symbols will be included

[Wei Mi via llvm-commits]

Author: Wei Mi
Date: 2021-02-27T23:15:31-08:00
New Revision: 7fb400112f6c41fc98ee5d584cdc0dfe76393a25

URL: https://github.com/llvm/llvm-project/commit/7fb400112f6c41fc98ee5d584cdc0dfe76393a25
DIFF: https://github.com/llvm/llvm-project/commit/7fb400112f6c41fc98ee5d584cdc0dfe76393a25.diff

LOG: [SampleFDO] Add a cutoff flag to control how many symbols will be included
into profile symbol list.

When test is unrepresentative to production behavior, sample profile
collected from production can cause unexpected performance behavior
in test. To triage such issue, it is useful to have a cutoff flag
to control how many symbols will be included into profile symbol list
in order to do binary search.

Differential Revision: https://reviews.llvm.org/D97623

Added: 
    

Modified: 
    llvm/lib/ProfileData/SampleProf.cpp
    llvm/test/Transforms/SampleProfile/Inputs/profile-symbol-list.text
    llvm/test/Transforms/SampleProfile/profile-sample-accurate.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/ProfileData/SampleProf.cpp b/llvm/lib/ProfileData/SampleProf.cpp
index d6acc00e1a6f..bca5b45c2151 100644
--- a/llvm/lib/ProfileData/SampleProf.cpp
+++ b/llvm/lib/ProfileData/SampleProf.cpp
@@ -16,6 +16,7 @@
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/PseudoProbe.h"
 #include "llvm/ProfileData/SampleProfReader.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Error.h"
@@ -29,6 +30,11 @@
 using namespace llvm;
 using namespace sampleprof;
 
+static cl::opt<uint64_t> ProfileSymbolListCutOff(
+    "profile-symbol-list-cutoff", cl::Hidden, cl::init(-1), cl::ZeroOrMore,
+    cl::desc("Cutoff value about how many symbols in profile symbol list "
+             "will be used. This is very useful for performance debugging"));
+
 namespace llvm {
 namespace sampleprof {
 SampleProfileFormat FunctionSamples::Format;
@@ -274,12 +280,14 @@ std::error_code ProfileSymbolList::read(const uint8_t *Data,
                                         uint64_t ListSize) {
   const char *ListStart = reinterpret_cast<const char *>(Data);
   uint64_t Size = 0;
-  while (Size < ListSize) {
+  uint64_t StrNum = 0;
+  while (Size < ListSize && StrNum < ProfileSymbolListCutOff) {
     StringRef Str(ListStart + Size);
     add(Str);
     Size += Str.size() + 1;
+    StrNum++;
   }
-  if (Size != ListSize)
+  if (Size != ListSize && StrNum != ProfileSymbolListCutOff)
     return sampleprof_error::malformed;
   return sampleprof_error::success;
 }

diff  --git a/llvm/test/Transforms/SampleProfile/Inputs/profile-symbol-list.text b/llvm/test/Transforms/SampleProfile/Inputs/profile-symbol-list.text
index 3763872a229c..f7a5f22cc8a2 100644
--- a/llvm/test/Transforms/SampleProfile/Inputs/profile-symbol-list.text
+++ b/llvm/test/Transforms/SampleProfile/Inputs/profile-symbol-list.text
@@ -1,5 +1,6 @@
 _Z3goov
 _Z3sumii
+_Z3toov
 __libc_csu_fini
 __libc_csu_init
 _dl_relocate_static_pie

diff  --git a/llvm/test/Transforms/SampleProfile/profile-sample-accurate.ll b/llvm/test/Transforms/SampleProfile/profile-sample-accurate.ll
index dfd8fd9577f7..0ac80fe11750 100644
--- a/llvm/test/Transforms/SampleProfile/profile-sample-accurate.ll
+++ b/llvm/test/Transforms/SampleProfile/profile-sample-accurate.ll
@@ -6,6 +6,8 @@
 ; RUN: llvm-profdata merge -sample -extbinary -prof-sym-list=%S/Inputs/profile-symbol-list.text %S/Inputs/profsampleacc.extbinary.afdo -o %t.symlist.afdo
 ; RUN: opt < %s -sample-profile -sample-profile-file=%t.symlist.afdo -profile-summary-cutoff-hot=600000 -profile-accurate-for-symsinlist -enable-new-pm=0 -S | FileCheck %s --check-prefix=PROFSYMLIST
 ; RUN: opt < %s -passes=sample-profile -sample-profile-file=%t.symlist.afdo -profile-summary-cutoff-hot=600000 -profile-accurate-for-symsinlist -S | FileCheck %s --check-prefix=PROFSYMLIST
+; RUN: opt < %s -passes=sample-profile -sample-profile-file=%t.symlist.afdo -profile-accurate-for-symsinlist -profile-symbol-list-cutoff=2 -S | FileCheck %s --check-prefix=PSLCUTOFF2
+; RUN: opt < %s -passes=sample-profile -sample-profile-file=%t.symlist.afdo -profile-accurate-for-symsinlist -profile-symbol-list-cutoff=3 -S | FileCheck %s --check-prefix=PSLCUTOFF3
 ;
 ; If -profile-accurate-for-symsinlist and -profile-sample-accurate both present,
 ; -profile-sample-accurate will override -profile-accurate-for-symsinlist.
@@ -60,6 +62,16 @@ entry:
   ret i32 %add, !dbg !11
 }
 
+; Check -profile-symbol-list-cutoff=3 will include _Z3toov into profile
+; symbol list and -profile-symbol-list-cutoff=2 will not.
+; PSLCUTOFF2: define i32 @_Z3toov{{.*}}!prof ![[TOO_ID:[0-9]+]]
+; PSLCUTOFF3: define i32 @_Z3toov{{.*}}!prof ![[TOO_ID:[0-9]+]]
+define i32 @_Z3toov(i32 %x, i32 %y) #0 {
+entry:
+  %add = add nsw i32 %x, %y
+  ret i32 %add
+}
+
 ; Function Attrs: uwtable
 define i32 @main() #0 !dbg !7 {
 entry:
@@ -132,6 +144,8 @@ attributes #0 = { "use-sample-profile" }
 ; CALL_SUM_IS_HOT: ![[ZERO_ID]] = !{!"function_entry_count", i64 0}
 ; CALL_SUM_IS_WARM: ![[NONZERO_ID]] = !{!"function_entry_count", i64 5179}
 ; PROFSYMLIST: ![[UNKNOWN_ID]] = !{!"function_entry_count", i64 -1}
+; PSLCUTOFF2: ![[TOO_ID]] = !{!"function_entry_count", i64 -1}
+; PSLCUTOFF3: ![[TOO_ID]] = !{!"function_entry_count", i64 0}
 !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.5 ", isOptimized: false, emissionKind: NoDebug, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
 !1 = !DIFile(filename: "calls.cc", directory: ".")
 !2 = !{}