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timers: improve Timer.now() performance
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Record the start time so we can make the return value of Timer.now()
relative to it, increasing the chances that it fits in a tagged integer
instead of a heap-allocated double, at least for the first one or two
billion milliseconds.

PR-URL: #2256
Reviewed-By: Trevor Norris <[email protected]>
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bnoordhuis committed Jul 27, 2015
1 parent 3663b12 commit 543dabb
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Showing 4 changed files with 17 additions and 0 deletions.
5 changes: 5 additions & 0 deletions src/env-inl.h
Original file line number Diff line number Diff line change
Expand Up @@ -171,6 +171,7 @@ inline Environment::Environment(v8::Local<v8::Context> context,
uv_loop_t* loop)
: isolate_(context->GetIsolate()),
isolate_data_(IsolateData::GetOrCreate(context->GetIsolate(), loop)),
timer_base_(uv_now(loop)),
using_smalloc_alloc_cb_(false),
using_domains_(false),
using_abort_on_uncaught_exc_(false),
Expand Down Expand Up @@ -286,6 +287,10 @@ inline Environment::TickInfo* Environment::tick_info() {
return &tick_info_;
}

inline uint64_t Environment::timer_base() const {
return timer_base_;
}

inline bool Environment::using_smalloc_alloc_cb() const {
return using_smalloc_alloc_cb_;
}
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2 changes: 2 additions & 0 deletions src/env.h
Original file line number Diff line number Diff line change
Expand Up @@ -398,6 +398,7 @@ class Environment {
inline AsyncHooks* async_hooks();
inline DomainFlag* domain_flag();
inline TickInfo* tick_info();
inline uint64_t timer_base() const;

static inline Environment* from_cares_timer_handle(uv_timer_t* handle);
inline uv_timer_t* cares_timer_handle();
Expand Down Expand Up @@ -501,6 +502,7 @@ class Environment {
AsyncHooks async_hooks_;
DomainFlag domain_flag_;
TickInfo tick_info_;
const uint64_t timer_base_;
uv_timer_t cares_timer_handle_;
ares_channel cares_channel_;
ares_task_list cares_task_list_;
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2 changes: 2 additions & 0 deletions src/timer_wrap.cc
Original file line number Diff line number Diff line change
Expand Up @@ -101,6 +101,8 @@ class TimerWrap : public HandleWrap {
Environment* env = Environment::GetCurrent(args);
uv_update_time(env->event_loop());
uint64_t now = uv_now(env->event_loop());
CHECK(now >= env->timer_base());
now -= env->timer_base();
if (now <= 0xfffffff)
args.GetReturnValue().Set(static_cast<uint32_t>(now));
else
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8 changes: 8 additions & 0 deletions test/parallel/test-timers-now.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
'use strict';

const common = require('../common');
const assert = require('assert');

// Return value of Timer.now() should easily fit in a SMI right after start-up.
const Timer = process.binding('timer_wrap').Timer;
assert(Timer.now() < 0x3ffffff);

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