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[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
This commit is contained in:
Wei Mi 2021-02-27 21:44:28 -08:00
parent b3c2821400
commit 7fb400112f
3 changed files with 25 additions and 2 deletions
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12
llvm/lib/ProfileData/SampleProf.cpp
View File

@ -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;
}

1
llvm/test/Transforms/SampleProfile/Inputs/profile-symbol-list.text
View File

@ -1,5 +1,6 @@
_Z3goov
_Z3sumii
_Z3toov
__libc_csu_fini
__libc_csu_init
_dl_relocate_static_pie

14
llvm/test/Transforms/SampleProfile/profile-sample-accurate.ll
View File

@ -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 = !{}