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timers: cross JS/C++ border less frequently

This removes the `process._needImmediateCallback` property
and its semantics of having a 1/0 switch that tells C++ whether
immediates are currently scheduled.

Instead, a counter keeping track of all immediates is created,
that can be increased on `setImmediate()` or decreased when an
immediate is run or cleared.

This is faster, because rather than reading/writing a C++ getter,
this operation can be performed as a direct memory read/write via
a typed array. The only C++ call that is left to make is
activating the native handles upon creation of the first
`Immediate` after the queue is empty.

One other (good!) side-effect is that `immediate._destroyed` now
reliably tells whether an `immediate` is still scheduled to run or not.

Also, as a nice extra, this should make it easier to implement
an internal variant of `setImmediate` for C++ that piggybacks
off the same mechanism, which should be useful at least for
async hooks and HTTP/2.

Benchmark results:

    $ ./node benchmark/compare.js --new ./node --old ./node-master-1b093cb93df0 --runs 10 --filter immediate timers | Rscript benchmark/compare.R
    [00:08:53|% 100| 4/4 files | 20/20 runs | 1/1 configs]: Done
                                                         improvement confidence      p.value
     timers/immediate.js type="breadth" thousands=2000      25.61 %         ** 1.432301e-03
     timers/immediate.js type="breadth1" thousands=2000      7.66 %            1.320233e-01
     timers/immediate.js type="breadth4" thousands=2000      4.61 %            5.669053e-01
     timers/immediate.js type="clear" thousands=2000       311.40 %        *** 3.896291e-07
     timers/immediate.js type="depth" thousands=2000        17.54 %         ** 9.755389e-03
     timers/immediate.js type="depth1" thousands=2000       17.09 %        *** 7.176229e-04
     timers/set-immediate-breadth-args.js millions=5        10.63 %          * 4.250034e-02
     timers/set-immediate-breadth.js millions=10            20.62 %        *** 9.150439e-07
     timers/set-immediate-depth-args.js millions=10         17.97 %        *** 6.819135e-10

PR-URL: #17064
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
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addaleax committed Nov 15, 2017
1 parent ca3f9b7 commit ae558af7bc1db217eb1c368c8b5e5773910232c3
Showing with 69 additions and 73 deletions.
  1. +24 −22 lib/timers.js
  2. +6 −0 src/env-inl.h
  3. +4 −0 src/env.h
  4. +35 −51 src/node.cc
View
@@ -47,6 +47,13 @@ const { kInit, kDestroy, kAsyncIdCounter } = async_wrap.constants;
const async_id_symbol = Symbol('asyncId');
const trigger_async_id_symbol = Symbol('triggerAsyncId');
/* This is an Uint32Array for easier sharing with C++ land. */
const scheduledImmediateCount = process._scheduledImmediateCount;
delete process._scheduledImmediateCount;
/* Kick off setImmediate processing */
const activateImmediateCheck = process._activateImmediateCheck;
delete process._activateImmediateCheck;
// Timeout values > TIMEOUT_MAX are set to 1.
const TIMEOUT_MAX = 2147483647; // 2^31-1
@@ -742,15 +749,9 @@ function processImmediate() {
else
immediate = next;
}
// Only round-trip to C++ land if we have to. Calling clearImmediate() on an
// immediate that's in |queue| is okay. Worst case is we make a superfluous
// call to NeedImmediateCallbackSetter().
if (!immediateQueue.head) {
process._needImmediateCallback = false;
}
}
process._immediateCallback = processImmediate;
// An optimization so that the try/finally only de-optimizes (since at least v8
// 4.7) what is in this smaller function.
@@ -762,13 +763,17 @@ function tryOnImmediate(immediate, oldTail) {
runCallback(immediate);
threw = false;
} finally {
// clearImmediate checks _onImmediate === null for kDestroy hooks.
immediate._onImmediate = null;
if (!threw)
emitAfter(immediate[async_id_symbol]);
if (async_hook_fields[kDestroy] > 0 && !immediate._destroyed) {
emitDestroy(immediate[async_id_symbol]);
if (!immediate._destroyed) {
immediate._destroyed = true;
scheduledImmediateCount[0]--;
if (async_hook_fields[kDestroy] > 0) {
emitDestroy(immediate[async_id_symbol]);
}
}
if (threw && immediate._idleNext) {
@@ -870,10 +875,9 @@ function createImmediate(args, callback) {
immediate._argv = args;
immediate._onImmediate = callback;
if (!process._needImmediateCallback) {
process._needImmediateCallback = true;
process._immediateCallback = processImmediate;
}
if (scheduledImmediateCount[0] === 0)
activateImmediateCheck();
scheduledImmediateCount[0]++;
immediateQueue.append(immediate);
@@ -884,18 +888,16 @@ function createImmediate(args, callback) {
exports.clearImmediate = function(immediate) {
if (!immediate) return;
if (async_hook_fields[kDestroy] > 0 &&
immediate._onImmediate !== null &&
!immediate._destroyed) {
emitDestroy(immediate[async_id_symbol]);
if (!immediate._destroyed) {
scheduledImmediateCount[0]--;
immediate._destroyed = true;
if (async_hook_fields[kDestroy] > 0) {
emitDestroy(immediate[async_id_symbol]);
}
}
immediate._onImmediate = null;
immediateQueue.remove(immediate);
if (!immediateQueue.head) {
process._needImmediateCallback = false;
}
};
View
@@ -283,6 +283,7 @@ inline Environment::Environment(IsolateData* isolate_data,
abort_on_uncaught_exception_(false),
emit_napi_warning_(true),
makecallback_cntr_(0),
scheduled_immediate_count_(isolate_, 1),
#if HAVE_INSPECTOR
inspector_agent_(new inspector::Agent(this)),
#endif
@@ -512,6 +513,11 @@ inline void Environment::set_fs_stats_field_array(double* fields) {
fs_stats_field_array_ = fields;
}
inline AliasedBuffer<uint32_t, v8::Uint32Array>&
Environment::scheduled_immediate_count() {
return scheduled_immediate_count_;
}
inline performance::performance_state* Environment::performance_state() {
return performance_state_;
}
View
@@ -622,6 +622,8 @@ class Environment {
inline double* fs_stats_field_array() const;
inline void set_fs_stats_field_array(double* fields);
inline AliasedBuffer<uint32_t, v8::Uint32Array>& scheduled_immediate_count();
inline performance::performance_state* performance_state();
inline std::map<std::string, uint64_t>* performance_marks();
@@ -731,6 +733,8 @@ class Environment {
size_t makecallback_cntr_;
std::vector<double> destroy_async_id_list_;
AliasedBuffer<uint32_t, v8::Uint32Array> scheduled_immediate_count_;
performance::performance_state* performance_state_ = nullptr;
std::map<std::string, uint64_t> performance_marks_;
View
@@ -400,25 +400,6 @@ static void PrintErrorString(const char* format, ...) {
va_end(ap);
}
static void CheckImmediate(uv_check_t* handle) {
Environment* env = Environment::from_immediate_check_handle(handle);
HandleScope scope(env->isolate());
Context::Scope context_scope(env->context());
MakeCallback(env->isolate(),
env->process_object(),
env->immediate_callback_string(),
0,
nullptr,
{0, 0}).ToLocalChecked();
}
static void IdleImmediateDummy(uv_idle_t* handle) {
// Do nothing. Only for maintaining event loop.
// TODO(bnoordhuis) Maybe make libuv accept nullptr idle callbacks.
}
const char *signo_string(int signo) {
#define SIGNO_CASE(e) case e: return #e;
switch (signo) {
@@ -3019,39 +3000,40 @@ static void DebugEnd(const FunctionCallbackInfo<Value>& args);
namespace {
void NeedImmediateCallbackGetter(Local<Name> property,
const PropertyCallbackInfo<Value>& info) {
Environment* env = Environment::GetCurrent(info);
const uv_check_t* immediate_check_handle = env->immediate_check_handle();
bool active = uv_is_active(
reinterpret_cast<const uv_handle_t*>(immediate_check_handle));
info.GetReturnValue().Set(active);
bool MaybeStopImmediate(Environment* env) {
if (env->scheduled_immediate_count()[0] == 0) {
uv_check_stop(env->immediate_check_handle());
uv_idle_stop(env->immediate_idle_handle());
return true;
}
return false;
}
void CheckImmediate(uv_check_t* handle) {
Environment* env = Environment::from_immediate_check_handle(handle);
HandleScope scope(env->isolate());
Context::Scope context_scope(env->context());
void NeedImmediateCallbackSetter(
Local<Name> property,
Local<Value> value,
const PropertyCallbackInfo<void>& info) {
Environment* env = Environment::GetCurrent(info);
if (MaybeStopImmediate(env))
return;
uv_check_t* immediate_check_handle = env->immediate_check_handle();
bool active = uv_is_active(
reinterpret_cast<const uv_handle_t*>(immediate_check_handle));
MakeCallback(env->isolate(),
env->process_object(),
env->immediate_callback_string(),
0,
nullptr,
{0, 0}).ToLocalChecked();
if (active == value->BooleanValue())
return;
MaybeStopImmediate(env);
}
uv_idle_t* immediate_idle_handle = env->immediate_idle_handle();
if (active) {
uv_check_stop(immediate_check_handle);
uv_idle_stop(immediate_idle_handle);
} else {
uv_check_start(immediate_check_handle, CheckImmediate);
// Idle handle is needed only to stop the event loop from blocking in poll.
uv_idle_start(immediate_idle_handle, IdleImmediateDummy);
}
void ActivateImmediateCheck(const FunctionCallbackInfo<Value>& args) {
Environment* env = Environment::GetCurrent(args);
uv_check_start(env->immediate_check_handle(), CheckImmediate);
// Idle handle is needed only to stop the event loop from blocking in poll.
uv_idle_start(env->immediate_idle_handle(),
[](uv_idle_t*){ /* do nothing, just keep the loop running */ });
}
@@ -3277,12 +3259,11 @@ void SetupProcessObject(Environment* env,
FIXED_ONE_BYTE_STRING(env->isolate(), "ppid"),
GetParentProcessId).FromJust());
auto need_immediate_callback_string =
FIXED_ONE_BYTE_STRING(env->isolate(), "_needImmediateCallback");
CHECK(process->SetAccessor(env->context(), need_immediate_callback_string,
NeedImmediateCallbackGetter,
NeedImmediateCallbackSetter,
env->as_external()).FromJust());
auto scheduled_immediate_count =
FIXED_ONE_BYTE_STRING(env->isolate(), "_scheduledImmediateCount");
CHECK(process->Set(env->context(),
scheduled_immediate_count,
env->scheduled_immediate_count().GetJSArray()).FromJust());
// -e, --eval
if (eval_string) {
@@ -3408,6 +3389,9 @@ void SetupProcessObject(Environment* env,
env->as_external()).FromJust());
// define various internal methods
env->SetMethod(process,
"_activateImmediateCheck",
ActivateImmediateCheck);
env->SetMethod(process,
"_startProfilerIdleNotifier",
StartProfilerIdleNotifier);

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