我正在将dart与nodejs进行比较。
我重写了nodeJs应用程序来解析并返回到http客户端的大块json（大约1000个对象）。出于测试目的，从文件中读取json。然后将json解析为Map，转换为新的表示并响应客户端。
可以在此处找到示例应用mapping json sample app
当我增加对服务的并发呼叫数量时，我注意到响应时间的增加。
这里是10个并发线程处理40个请求的报告
document Length: 613480 bytes
Concurrency Level: 10
Time taken for tests: 9.079 seconds
Complete requests: 40
Failed requests: 0
Write errors: 0
Total transferred: 24542960 bytes
HTML transferred: 24539200 bytes
Requests per second: 4.41 [#/sec] (mean)
Time per request: 2269.770 [ms] (mean)
Time per request: 226.977 [ms] (mean, across all concurrent requests)
Transfer rate: 2639.89 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.8 0 5
Processing: 1250 2111 300.0 2126 2880
Waiting: 1024 1917 307.9 1948 2840
Total: 1255 2111 299.6 2126 2880
Percentage of the requests served within a certain time (ms)
50% 2126
66% 2213
75% 2233
80% 2243
90% 2446
95% 2865
98% 2880
99% 2880
100% 2880 (longest request)
注意如果仅使用2个并发线程，响应时间会下降
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.1 0 1
Processing: 279 447 140.9 415 1033
Waiting: 224 397 140.1 405 1000
Total: 279 447 140.9 415 1033
Percentage of the requests served within a certain time (ms)
50% 415
66% 422
75% 430
80% 434
90% 463
95% 1007
98% 1033
99% 1033
100% 1033 (longest request)
当只有一个客户端时，它是超快的
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.1 0 1
Processing: 189 207 14.7 205 265
Waiting: 186 205 14.5 203 262
Total: 189 207 14.7 205 265
Percentage of the requests served within a certain time (ms)
50% 205
66% 209
75% 214
80% 217
90% 224
95% 240
98% 265
99% 265
100% 265 (longest request)
以下是在同一数据和同一台机器上运行的节点的输出
Document Length: 807396 bytes
Concurrency Level: 10
Time taken for tests: 3.955 seconds
Complete requests: 40
Failed requests: 0
Write errors: 0
Total transferred: 32304320 bytes
HTML transferred: 32295840 bytes
Requests per second: 10.11 [#/sec] (mean)
Time per request: 988.661 [ms] (mean)
Time per request: 98.866 [ms] (mean, across all concurrent requests)
Transfer rate: 7977.25 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.5 0 3
Processing: 954 987 18.6 1000 1007
Waiting: 116 567 272.1 598 999
Total: 954 987 18.7 1001 1007
Percentage of the requests served within a certain time (ms)
50% 1001
66% 1004
75% 1004
80% 1004
90% 1005
95% 1005
98% 1007
99% 1007
100% 1007 (longest request)
据我所知，如果我在事件队列上放了很多事件，响应时间会增加。但我预计飞镖会使用微型机器来更早地处理等待事件。
这里是数据样本，结果数组总是包含1000个项目
{
"numFound": 1234,
"results": [
{
"cid": "id",
"cir": "id",
"cn": "name",
"cbr": "string",
"crn": "string",
"dep": "string",
"depid": "id",
"fn": "string",
"jvid": "id",
"loc": "string",
"pid": "id",
"date": int,
"toe": "string",
"ujn": "string",
"vn": "string",
"ind": "string",
"indid": "id",
"fun": "string",
"funid": "id",
"des": "string",
"date2": int,
"uuid": "string",
"elv": "string",
"elvid": "id",
"cfv": Array<Objects>
}
]
}
我正在使用centos 6.5（我已经建立了dart 1.2 sdk）。我用
运行应用程序perf record -g - dart --generate_perf_events_symbols start.dart
这就是'perf report --call-graph flat'所示，但我不知道如何解释输出以改进我的代码。
75.86% dart [kernel.kallsyms] [k] __do_softirq
+ 3.62% dart dart [.] dart::MarkingVisitor::VisitPointers(dart::RawObject**, dart::RawObject**)
+ 1.36% dart dart [.] dart::ScavengerVisitor::VisitPointers(dart::RawObject**, dart::RawObject**)
+ 1.02% dart dart [.] dart::GCSweeper::SweepPage(dart::HeapPage*, dart::FreeList*)
+ 0.96% dart perf-5465.map [.] *dart:core_StringBuffer_writeCharCode
+ 0.74% dart perf-5465.map [.] *dart:convert__Utf8Decoder@0xda80e0a_convert
+ 0.71% dart perf-5465.map [.] *dart:convert__JsonStringifier@0xda80e0a_escape
+ 0.57% dart perf-5465.map [.] *dart:convert__Utf8Encoder@0xda80e0a__fillBuffer@0xda80e0a
+ 0.55% dart libc-2.12.so [.] _wordcopy_fwd_aligned
0.53% dart [kernel.kallsyms] [k] retint_careful
+ 0.52% dart perf-5465.map [.] *dart:core_StringBuffer__addPart@0x36924d72
0.50% dart [kernel.kallsyms] [k] finish_task_switch
0.49% dart dart [.] dart::RawObject::VisitPointers(dart::ObjectPointerVisitor*)
0.41% dart [vsyscall] [.] 0x000000000000014c
0.38% dart libc-2.12.so [.] memmove
0.29% dart libpthread-2.12.so [.] pthread_getspecific
0.29% dart dart [.] dart::FreeList::TryAllocate(long, bool)
0.28% dart perf-5465.map [.] dart:core__List@0x36924d72__List@0x36924d72.
0.28% dart perf-5465.map [.] *dart:convert__JsonParser@0xda80e0a_parse
0.27% dart perf-5465.map [.] *dart:core_StringBuffer_write
0.27% dart perf-5465.map [.] *package:public-api/publicApi.dart_PostingResultMapper_mapPosting_mapPosting
0.27% dart [kernel.kallsyms] [k] _spin_unlock_irqrestore
0.27% dart dart [.] dart::String::Copy(dart::String const&, long, unsigned char const*, long)
0.27% dart dart [.] dart::VMHandles::AllocateHandle(dart::Isolate*)
0.26% dart perf-5465.map [.] *dart:collection__HashMap@0x23c35ea0&&_LinkedHashMapMixin@0x23c35ea0_forEach
0.25% dart perf-5465.map [.] *dart:convert__JsonStringifier@0xda80e0a_stringifyJsonValue
0.24% dart dart [.] dart::Object::Allocate(long, long, dart::Heap::Space)
0.24% dart perf-5465.map [.] dart:core__StringBase@0x36924d72_codeUnitAt
0.23% dart dart [.] dart::GCMarker::DrainMarkingStack(dart::Isolate*, dart::MarkingVisitor*)
0.22% dart dart [.] dart::ClassTable::UpdateLiveOld(long, long)
0.22% dart perf-5465.map [.] *dart:convert__JsonParser@0xda80e0a_parseString
0.21% dart perf-5465.map [.] *dart:convert__JsonParser@0xda80e0a_parseString
0.20% dart dart [.] dart::String::Copy(dart::String const&, long, dart::String const&, long, long)
0.17% dart dart [.] dart::OneByteString::ConcatAll(dart::Array const&, long, long, long, dart::Heap::Space)
0.16% dart [kernel.kallsyms] [k] __do_page_fault
0.16% dart dart [.] dart::BootstrapNatives::DN_StringBase_substringUnchecked(_Dart_NativeArguments*)
0.15% dart dart [.] dart::String::ConcatAllRange(dart::Array const&, long, long, dart::Heap::Space)
0.15% dart perf-5465.map [.] *dart:core_StringBuffer__consumeBuffer@0x36924d72
0.14% dart [kernel.kallsyms] [k] clear_page_c
0.13% dart perf-5465.map [.] _stub_OneArgCheckInlineCache
0.12% dart perf-5465.map [.] *dart:core__StringBase@0x36924d72_substring
0.11% dart dart [.] dart::String::Copy(dart::String const&, long, unsigned short const*, long)
0.11% dart perf-5465.map [.] *dart:collection__HashMap@0x23c35ea0&&_LinkedHashMapMixin@0x23c35ea0__addEntry@0x23c35ea0
0.11% dart dart [.] dart::String::SubString(dart::String const&, long, long, dart::Heap::Space)
0.11% dart dart [.] dart::FreeList::SplitElementAfterAndEnqueue(dart::FreeListElement*, long, bool)
0.10% dart [kernel.kallsyms] [k] get_page_from_freelist
0.10% dart dart [.] 0x000000000031b333
0.10% dart dart [.] dart::Scavenger::ProcessToSpace(dart::ScavengerVisitor*)
0.09% dart dart [.] dart::RawArray::VisitArrayPointers(dart::RawArray*, dart::ObjectPointerVisitor*)
0.09% dart dart [.] dart::ClassTable::UpdateAllocatedOld(long, long)
0.08% dart dart [.] dart::Profiler::RecordSampleInterruptCallback(dart::InterruptedThreadState const&, void*)
0.08% dart dart [.] dart::BootstrapNatives::DN_String_concatRange(_Dart_NativeArguments*)
0.08% dart perf-5465.map [.] *dart:convert__JsonStringifier@0xda80e0a_stringifyJsonValue_<anonymous closure>
0.07% dart perf-5465.map [.] _stub_TwoArgsCheckInlineCache
0.07% dart dart [.] dart::BootstrapNatives::DN_Object_getHash(_Dart_NativeArguments*)
0.07% dart perf-5465.map [.] *dart:core__Smi@0x36924d72_toString
0.07% dart perf-5465.map [.] dart:core__OneByteString@0x36924d72_get_hashCode
0.07% dart dart [.] dart::Instance::IsInstance() const
0.06% dart dart [.] dart::BootstrapNatives::DN_StringBuffer_createStringFromUint16Array(_Dart_NativeArguments*)
0.06% dart perf-5465.map [.] *dart:collection_Maps_mapToString
0.06% dart dart [.] dart::VMHandles::~VMHandles()
0.06% dart dart [.] dart::GCMarker::MarkObjects(dart::Isolate*, dart::PageSpace*, bool, bool)
0.06% dart dart [.] dart::PageSpace::TryAllocate(long, dart::HeapPage::PageType, dart::PageSpace::GrowthPolicy)
0.06% dart [kernel.kallsyms] [k] free_hot_cold_page
0.06% dart perf-5465.map [.] dart:core__StringBase@0x36924d72__substringUncheckedNative@0x36924d72
0.06% dart dart [.] dart::LoadOptimizer::Optimize()
0.06% dart dart [.] dart::Heap::AllocateNew(long)
答案 0 :(得分：1)
我只想总结一下我发现的有关dm在vm上的行为。在直接询问后发现变换是一个严重的问题。
这已经在最新版本中得到了改进，并且也应该包含在下一个稳定版本中。
请检查此错误https://code.google.com/p/dart/issues/detail?id=17659以及来自drt google论坛的对话本身https://groups.google.com/a/dartlang.org/forum/#!topic/misc/S0rGeyc9aQU
非常感谢Gunter，Anders和Greg在这里帮助我。