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perf: improve heap snapshot performance (#26229)

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Fixes #24509.

cherry-pick 2e2dc98 from v8
This commit is contained in:
Charles Kerr
2020-10-28 14:07:52 -05:00
committed by GitHub
parent ccbf615da0
commit 831e84504d
2 changed files with 135 additions and 0 deletions
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1
patches/v8/.patches
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@@ -7,3 +7,4 @@ workaround_an_undefined_symbol_error.patch
do_not_export_private_v8_symbols_on_windows.patch
revert_cleanup_switch_offset_of_to_offsetof_where_possible.patch
fix_build_deprecated_attirbute_for_older_msvc_versions.patch
perf_make_getpositioninfoslow_faster.patch

134
patches/v8/perf_make_getpositioninfoslow_faster.patch Normal file
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@@ -0,0 +1,134 @@
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Charles Kerr <charles@charleskerr.com>
Date: Mon, 26 Oct 2020 16:53:25 -0500
Subject: perf: make GetPositionInfoSlow() faster
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Halve the number of lookups in ExtractLocationForJSFunction() by calling
GetPositionInfo() directly instead of making separate calls for column
and line number.
Improve the efficiency of position lookups in slow mode. The current
code does a linear walk through the source by calling String::Get() for
each character. This PR also does a linear walk, but avoids the overhead
of multiple Get() calls by pulling the String's flat content into a
local vector and walking through that.
Downstream Electron discussion of this can be found at
https://github.com/electron/electron/issues/24509
Change-Id: I22b034dc1bfe967164d2f8515a9a0c1d7f043c83
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2496065
Commit-Queue: Simon Zünd <szuend@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70783}
diff --git a/AUTHORS b/AUTHORS
index 7c43c60fc13af2a793547a9e5ef689e380ef565f..31a46b9bec0757c78650124793ba30def5f438f7 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -69,6 +69,7 @@ Bert Belder <bertbelder@gmail.com>
Burcu Dogan <burcujdogan@gmail.com>
Caitlin Potter <caitpotter88@gmail.com>
Craig Schlenter <craig.schlenter@gmail.com>
+Charles Kerr <charles@charleskerr.com>
Chengzhong Wu <legendecas@gmail.com>
Choongwoo Han <cwhan.tunz@gmail.com>
Chris Nardi <hichris123@gmail.com>
diff --git a/src/objects/objects.cc b/src/objects/objects.cc
index 3ef1067d9f956cba708475aa2beb87dcc5df261b..5e0c831f73b6ccbe40c556497f5ba6fbc9f42b48 100644
--- a/src/objects/objects.cc
+++ b/src/objects/objects.cc
@@ -4785,30 +4785,43 @@ bool Script::ContainsAsmModule() {
}
namespace {
-bool GetPositionInfoSlow(const Script script, int position,
- Script::PositionInfo* info) {
- if (!script.source().IsString()) return false;
- if (position < 0) position = 0;
- String source_string = String::cast(script.source());
+template <typename Char>
+bool GetPositionInfoSlowImpl(const Vector<Char>& source, int position,
+ Script::PositionInfo* info) {
+ if (position < 0) {
+ position = 0;
+ }
int line = 0;
- int line_start = 0;
- int len = source_string.length();
- for (int pos = 0; pos <= len; ++pos) {
- if (pos == len || source_string.Get(pos) == '\n') {
- if (position <= pos) {
- info->line = line;
- info->column = position - line_start;
- info->line_start = line_start;
- info->line_end = pos;
- return true;
- }
- line++;
- line_start = pos + 1;
+ const auto begin = std::cbegin(source);
+ const auto end = std::cend(source);
+ for (auto line_begin = begin; line_begin < end;) {
+ const auto line_end = std::find(line_begin, end, '\n');
+ if (position <= (line_end - begin)) {
+ info->line = line;
+ info->column = static_cast<int>((begin + position) - line_begin);
+ info->line_start = static_cast<int>(line_begin - begin);
+ info->line_end = static_cast<int>(line_end - begin);
+ return true;
}
+ ++line;
+ line_begin = line_end + 1;
}
return false;
}
+bool GetPositionInfoSlow(const Script script, int position,
+ const DisallowHeapAllocation& no_gc,
+ Script::PositionInfo* info) {
+ if (!script.source().IsString()) {
+ return false;
+ }
+ auto source = String::cast(script.source());
+ const auto flat = source.GetFlatContent(no_gc);
+ return flat.IsOneByte()
+ ? GetPositionInfoSlowImpl(flat.ToOneByteVector(), position, info)
+ : GetPositionInfoSlowImpl(flat.ToUC16Vector(), position, info);
+}
+
} // namespace
bool Script::GetPositionInfo(int position, PositionInfo* info,
@@ -4830,7 +4843,9 @@ bool Script::GetPositionInfo(int position, PositionInfo* info,
if (line_ends().IsUndefined()) {
// Slow mode: we do not have line_ends. We have to iterate through source.
- if (!GetPositionInfoSlow(*this, position, info)) return false;
+ if (!GetPositionInfoSlow(*this, position, no_allocation, info)) {
+ return false;
+ }
} else {
DCHECK(line_ends().IsFixedArray());
FixedArray ends = FixedArray::cast(line_ends());
diff --git a/src/profiler/heap-snapshot-generator.cc b/src/profiler/heap-snapshot-generator.cc
index 2fa4f2e5e841bbbf98580dee241fac00899e780e..8f98451488052ba34a59635b707aa5bd3d086161 100644
--- a/src/profiler/heap-snapshot-generator.cc
+++ b/src/profiler/heap-snapshot-generator.cc
@@ -573,9 +573,9 @@ void V8HeapExplorer::ExtractLocationForJSFunction(HeapEntry* entry,
Script script = Script::cast(func.shared().script());
int scriptId = script.id();
int start = func.shared().StartPosition();
- int line = script.GetLineNumber(start);
- int col = script.GetColumnNumber(start);
- snapshot_->AddLocation(entry, scriptId, line, col);
+ Script::PositionInfo info;
+ script.GetPositionInfo(start, &info, Script::WITH_OFFSET);
+ snapshot_->AddLocation(entry, scriptId, info.line, info.column);
}
HeapEntry* V8HeapExplorer::AddEntry(HeapObject object) {