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buffer: ~2x slowdown in master compared to v12.x #32226
Description
- Version: master
- Platform:
Linux foo 5.0.0-36-generic #39~18.04.1-Ubuntu SMP Tue Nov 12 11:09:50 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux - Subsystem: buffer
I was running some benchmarks (for private code) and noticed a significant slowdown with some Buffer methods. Here is a comparison of the C++ portion of --prof between v12.16.1 and master:
v12.16.1:
Details
[C++]:
ticks total nonlib name
66 4.2% 8.4% void node::Buffer::(anonymous namespace)::StringSlice<(node::encoding)1>(v8::FunctionCallbackInfo<v8::Value> const&)
54 3.4% 6.9% __libc_read
48 3.0% 6.1% node::Buffer::(anonymous namespace)::ParseArrayIndex(node::Environment*, v8::Local<v8::Value>, unsigned long, unsigned long*)
35 2.2% 4.5% v8::ArrayBuffer::GetContents()
35 2.2% 4.5% epoll_pwait
27 1.7% 3.4% v8::internal::Builtin_TypedArrayPrototypeBuffer(int, unsigned long*, v8::internal::Isolate*)
26 1.6% 3.3% v8::String::NewFromUtf8(v8::Isolate*, char const*, v8::NewStringType, int)
24 1.5% 3.1% node::native_module::NativeModuleEnv::CompileFunction(v8::FunctionCallbackInfo<v8::Value> const&)
22 1.4% 2.8% __pthread_cond_signal
20 1.3% 2.5% node::StringBytes::Encode(v8::Isolate*, char const*, unsigned long, node::encoding, v8::Local<v8::Value>*)
16 1.0% 2.0% v8::Value::IsArrayBufferView() const
14 0.9% 1.8% v8::ArrayBufferView::Buffer()
9 0.6% 1.1% v8::internal::FixedArray::set(int, v8::internal::Object)
8 0.5% 1.0% v8::ArrayBufferView::ByteLength()
7 0.4% 0.9% v8::Value::IntegerValue(v8::Local<v8::Context>) const
6 0.4% 0.8% v8::ArrayBufferView::ByteOffset()
5 0.3% 0.6% __libc_malloc
4 0.3% 0.5% write
4 0.3% 0.5% v8::internal::libc_memmove(void*, void const*, unsigned long)
4 0.3% 0.5% node::binding::GetInternalBinding(v8::FunctionCallbackInfo<v8::Value> const&)
3 0.2% 0.4% v8::internal::libc_memset(void*, int, unsigned long)
3 0.2% 0.4% __lll_unlock_wake
2 0.1% 0.3% void node::StreamBase::JSMethod<&node::StreamBase::WriteBuffer>(v8::FunctionCallbackInfo<v8::Value> const&)
2 0.1% 0.3% fwrite
2 0.1% 0.3% do_futex_wait.constprop.1
2 0.1% 0.3% __clock_gettime
2 0.1% 0.3% __GI___pthread_mutex_unlock
1 0.1% 0.1% void node::StreamBase::JSMethod<&(int node::StreamBase::WriteString<(node::encoding)1>(v8::FunctionCallbackInfo<v8::Value> const&))>(v8::FunctionCallbackInfo<v8::Value> const&)
1 0.1% 0.1% v8::internal::Scope::DeserializeScopeChain(v8::internal::Isolate*, v8::internal::Zone*, v8::internal::ScopeInfo, v8::internal::DeclarationScope*, v8::internal::AstValueFactory*, v8::internal::Scope::DeserializationMode)
1 0.1% 0.1% v8::internal::RuntimeCallTimerScope::RuntimeCallTimerScope(v8::internal::Isolate*, v8::internal::RuntimeCallCounterId)
1 0.1% 0.1% v8::EscapableHandleScope::Escape(unsigned long*)
1 0.1% 0.1% std::ostreambuf_iterator<char, std::char_traits<char> > std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_M_insert_int<long>(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, long) const
1 0.1% 0.1% std::ostream::sentry::sentry(std::ostream&)
1 0.1% 0.1% std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)
1 0.1% 0.1% std::__detail::_Prime_rehash_policy::_M_need_rehash(unsigned long, unsigned long, unsigned long) const
1 0.1% 0.1% non-virtual thunk to node::LibuvStreamWrap::GetAsyncWrap()
1 0.1% 0.1% node::LibuvStreamWrap::ReadStart()::{lambda(uv_stream_s*, long, uv_buf_t const*)#2}::_FUN(uv_stream_s*, long, uv_buf_t const*)
1 0.1% 0.1% node::CustomBufferJSListener::OnStreamRead(long, uv_buf_t const&)
1 0.1% 0.1% node::AsyncWrap::EmitTraceEventBefore()
1 0.1% 0.1% mprotect
1 0.1% 0.1% getpid
1 0.1% 0.1% cfree
1 0.1% 0.1% __lll_lock_wait
master:
Details
[C++]:
ticks total nonlib name
155 6.5% 14.0% std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release()
88 3.7% 7.9% __GI___pthread_mutex_lock
87 3.7% 7.8% v8::ArrayBuffer::GetBackingStore()
71 3.0% 6.4% __GI___pthread_mutex_unlock
54 2.3% 4.9% void node::Buffer::(anonymous namespace)::StringSlice<(node::encoding)1>(v8::FunctionCallbackInfo<v8::Value> const&)
36 1.5% 3.2% node::Buffer::(anonymous namespace)::ParseArrayIndex(node::Environment*, v8::Local<v8::Value>, unsigned long, unsigned long*)
32 1.4% 2.9% v8::internal::Builtin_TypedArrayPrototypeBuffer(int, unsigned long*, v8::internal::Isolate*)
31 1.3% 2.8% v8::Value::IntegerValue(v8::Local<v8::Context>) const
27 1.1% 2.4% node::native_module::NativeModuleEnv::CompileFunction(v8::FunctionCallbackInfo<v8::Value> const&)
27 1.1% 2.4% epoll_pwait
26 1.1% 2.3% v8::String::NewFromUtf8(v8::Isolate*, char const*, v8::NewStringType, int)
20 0.8% 1.8% v8::Value::IsArrayBufferView() const
20 0.8% 1.8% __libc_read
19 0.8% 1.7% __pthread_cond_signal
16 0.7% 1.4% node::StringBytes::Encode(v8::Isolate*, char const*, unsigned long, node::encoding, v8::Local<v8::Value>*)
13 0.5% 1.2% v8::ArrayBufferView::Buffer()
10 0.4% 0.9% v8::internal::FixedArray::set(int, v8::internal::Object)
6 0.3% 0.5% v8::internal::libc_memset(void*, int, unsigned long)
6 0.3% 0.5% v8::internal::RuntimeCallTimerScope::RuntimeCallTimerScope(v8::internal::Isolate*, v8::internal::RuntimeCallCounterId)
5 0.2% 0.5% v8::internal::libc_memmove(void*, void const*, unsigned long)
5 0.2% 0.5% v8::ArrayBufferView::ByteLength()
4 0.2% 0.4% write
4 0.2% 0.4% void node::StreamBase::JSMethod<&node::StreamBase::WriteBuffer>(v8::FunctionCallbackInfo<v8::Value> const&)
4 0.2% 0.4% do_futex_wait.constprop.1
4 0.2% 0.4% __lll_lock_wait
3 0.1% 0.3% node::binding::GetInternalBinding(v8::FunctionCallbackInfo<v8::Value> const&)
3 0.1% 0.3% _init
2 0.1% 0.2% v8::BackingStore::Data() const
2 0.1% 0.2% fwrite
2 0.1% 0.2% cfree
2 0.1% 0.2% __lll_unlock_wake
2 0.1% 0.2% __libc_malloc
1 0.0% 0.1% v8::internal::DeclarationScope::DeclareDefaultFunctionVariables(v8::internal::AstValueFactory*)
1 0.0% 0.1% v8::internal::Builtin_HandleApiCall(int, unsigned long*, v8::internal::Isolate*)
1 0.0% 0.1% v8::internal::AstValueFactory::GetOneByteStringInternal(v8::internal::Vector<unsigned char const>)
1 0.0% 0.1% std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::do_put(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, long) const
1 0.0% 0.1% operator new[](unsigned long)
1 0.0% 0.1% node::contextify::ContextifyContext::CompileFunction(v8::FunctionCallbackInfo<v8::Value> const&)
1 0.0% 0.1% node::TCPWrap::Connect(v8::FunctionCallbackInfo<v8::Value> const&)
1 0.0% 0.1% node::Environment::RunAndClearNativeImmediates(bool)
1 0.0% 0.1% node::AsyncWrap::EmitTraceEventBefore()
1 0.0% 0.1% mprotect
1 0.0% 0.1% __pthread_cond_timedwait
1 0.0% 0.1% __fxstat
1 0.0% 0.1% __GI___pthread_getspecific
As you will see, master has these additional items at the top of the list:
155 6.5% 14.0% std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release()
88 3.7% 7.9% __GI___pthread_mutex_lock
87 3.7% 7.8% v8::ArrayBuffer::GetBackingStore()
71 3.0% 6.4% __GI___pthread_mutex_unlock
Is there some way we can avoid this slowdown?
Activity
addaleax commentedon Mar 12, 2020
@mscdex Can you provide the output
uname -a(what the issue template asks for forPlatform:)? Is this on arm/arm64/x86/x64/something else? That’s probably relevant here.mscdex commentedon Mar 12, 2020
Added.
mscdex commentedon Mar 12, 2020
Additionally, I'm using gcc 7.4.0 to compile if that matters.
mmarchini commentedon Mar 12, 2020
Can you try #32116? If this is some regression on V8, it might already be fixed (or it might be worse on 8.1, but let's hope not).
addaleax commentedon Mar 12, 2020
The prof output makes it seem like the reason is that
std::shared_ptras we compile it on x64 seems to not use atomic instructions, but rather mutexes. I don’t quite know why it does that, but it’s probably something that can be addressed by passing compile flags. (That might be ABI-breaking but we could do it for v14.x, see #30786 for a related ARM issue.)Or it’s unrelated to that, but that’s not what the prof output says.
mscdex commentedon Mar 12, 2020
@mmarchini The V8 8.1 branch has the same performance as master.
addaleax commentedon Mar 12, 2020
(__gnu_cxx::_Lock_policy)2is_S_atomic, though, so … not quite sure that that’s actually responsible for the mutex lock/unlock calls.mscdex commentedon Mar 12, 2020
I've also now tried:
Compiling v12.16.1 locally (was using the binary from the website before)
Compiling master with gcc 9.2.1
Compiling master with
-march=nativeRemoving calls to
GetBackingStore()where possibleReverting to
GetContents()in placesAll changes made little to no difference.
mmarchini commentedon Mar 12, 2020
@mscdex do you see similar results with any of the benchmarks from benchmark/buffers? Maybe some benchmark similar to your private code?
mscdex commentedon Mar 12, 2020
@mmarchini Yes, for example:
mscdex commentedon Mar 12, 2020
The
--prof-processoutput for thatbuffer-tostringbenchmark shows basically the same top results as I showed originally.puzpuzpuz commentedon Mar 13, 2020
If that helps, I can also see the same performance degradation on 4.15.0-88-generic #88-Ubuntu SMP Tue Feb 11 20:11:34 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux, gcc 7.5.0:
68 remaining items
src: remove usages of GetBackingStore in node-api
src: remove unowned usages of GetBackingStore
src: remove usages of GetBackingStore in crypto
BridgeAR commentedon Sep 12, 2025
Seems like the bug got fixed by now. Closing
use ArrayBuffer->Data() when available
use ArrayBuffer->Data() when available