Consider removing fiber_pool.js

[laverdet]

Fibers already maintains a pool on the backend so it seems like you're just wasting cycles here. See: coroutine.cc

You can tweak the pool size dynamically with Fiber.poolSize, default is 120.

[benjamn]

You're suggesting I can just keep creating new Fiber objects and they'll get recycled into the pool as soon as they finish a given run? I don't have to wait for them to be garbage collected?

[laverdet]

As soon as a fiber finishes running its stack (which is the bulk of allocated memory) is returned to a shared pool. Garbage collection just cleans up the v8 handle which won't be a measurable performance cost in any application.

[And-re]

We are experiencing some performance issues in chimp which uses meteor-promise package. With node 6.3.1 it works ok but with node 7.3.0 it's getting slower and slower with every test.

I just used simple profiling https://nodejs.org/en/docs/guides/simple-profiling/ and here are the results (notice fiber_pool.js showing up for node 7.3.0) :

node 6.3.1 + meteor-promise 0.7.4

[Bottom up (heavy) profile]:
  Note: percentage shows a share of a particular caller in the total
  amount of its parent calls.
  Callers occupying less than 2.0% are not shown.

   ticks parent  name
  17100   47.8%  ___mac_get_pid

   2570    7.2%  UNKNOWN
    107    4.2%    LazyCompile: *readableAddChunk _stream_readable.js:148:26
    106   99.1%      LazyCompile: *onread net.js:524:16

   1465    4.1%  /Users/and_re/.nvm/versions/node/v6.3.1/bin/node
    243   16.6%    v8::internal::Builtins::~Builtins()
...

node 7.3.0 + meteor-promise 0.7.4

[Bottom up (heavy) profile]:
  Note: percentage shows a share of a particular caller in the total
  amount of its parent calls.
  Callers occupying less than 2.0% are not shown.

   ticks parent  name
  94616   18.4%  UNKNOWN
   9887   10.4%    v8::internal::Builtin_HandleApiCall(int, v8::internal::Object**, v8::internal::Isolate*)
   9873   99.9%      LazyCompile: *<anonymous> /Users/and_re/Projects/chimp-issue-6.3.1/node_modules/chimp/node_modules/meteor-promise/fiber_pool.js:14:36
   6132    6.5%    LazyCompile: ~t native promise.js:31:7
   1831   29.9%      LazyCompile: *<anonymous> /Users/and_re/Projects/chimp-issue-6.3.1/node_modules/chimp/node_modules/meteor-promise/fiber_pool.js:14:36
   3933    4.2%    LazyCompile: *<anonymous> /Users/and_re/Projects/chimp-issue-6.3.1/node_modules/chimp/node_modules/meteor-promise/fiber_pool.js:14:36

  17599    3.4%  v8::internal::JSObjectWalkVisitor<v8::internal::AllocationSiteUsageContext>::StructureWalk(v8::internal::Handle<v8::internal::JSObject>)
  17592  100.0%    v8::internal::Runtime_CreateObjectLiteral(int, v8::internal::Object**, v8::internal::Isolate*)
  12182   69.2%      LazyCompile: ~CreateResolvingFunctions native promise.js:29:34
   3764   30.9%        LazyCompile: *NewPromiseCapability native promise.js:227:30

  17358    3.4%  bool v8::internal::ScavengingVisitor<(v8::internal::MarksHandling)1, (v8::internal::PromotionMode)1, (v8::internal::LoggingAndProfiling)0>::SemiSpaceCopyObject<(v8::internal::AllocationAlignment)0>(v8::internal::Map*, v8::internal::HeapObject**, v8::internal::HeapObject*, int)
...

node 7.3.0 + meteor-promise 0.8.0

[Bottom up (heavy) profile]:
  Note: percentage shows a share of a particular caller in the total
  amount of its parent calls.
  Callers occupying less than 2.0% are not shown.

   ticks parent  name
  65986   12.6%  UNKNOWN
   9780   14.8%    v8::internal::Builtin_HandleApiCall(int, v8::internal::Object**, v8::internal::Isolate*)
   9767   99.9%      LazyCompile: *<anonymous> /Users/and_re/Projects/chimp-issue/node_modules/xolvio-sync-webdriverio/node_modules/meteor-promise/fiber_pool.js:14:36
   1455    2.2%    LazyCompile: ~<anonymous> /Users/and_re/Projects/chimp-issue/node_modules/xolvio-sync-webdriverio/node_modules/meteor-promise/fiber_pool.js:84:40
   1455  100.0%      LazyCompile: *FiberPool.run /Users/and_re/Projects/chimp-issue/node_modules/xolvio-sync-webdriverio/node_modules/meteor-promise/fiber_pool.js:69:23
   1454   99.9%        LazyCompile: ~result /Users/and_re/Projects/chimp-issue/node_modules/xolvio-sync-webdriverio/node_modules/meteor-promise/promise_server.js:134:25
   1454  100.0%          LazyCompile: *PromiseHandle native promise.js:94:23
   1454  100.0%            LazyCompile: ~<anonymous> native promise.js:108:27

  18446    3.5%  v8::internal::JSObjectWalkVisitor<v8::internal::AllocationSiteUsageContext>::StructureWalk(v8::internal::Handle<v8::internal::JSObject>)
  18437  100.0%    v8::internal::Runtime_CreateObjectLiteral(int, v8::internal::Object**, v8::internal::Isolate*)
  12345   67.0%      LazyCompile: ~CreateResolvingFunctions native promise.js:29:34
   5060   41.0%        LazyCompile: *Promise native promise.js:47:23
   5059  100.0%          LazyCompile: *FiberPool.run /Users/and_re/Projects/chimp-issue/node_modules/xolvio-sync-webdriverio/node_modules/meteor-promise/fiber_pool.js:69:23
   5056   99.9%            LazyCompile: ~result /Users/and_re/Projects/chimp-issue/node_modules/xolvio-sync-webdriverio/node_modules/meteor-promise/promise_server.js:134:25
   3702   30.0%        LazyCompile: ~<anonymous> native promise.js:194:27
   1078   29.1%          Stub: CallApiCallbackStub {2}
   1078  100.0%            LazyCompile: *_tickDomainCallback internal/process/next_tick.js:108:31
   3583   29.0%        LazyCompile: *NewPromiseCapability native promise.js:227:30
   3583  100.0%          LazyCompile: *then native promise.js:302:21
   3583  100.0%            LazyCompile: *Promise.then /Users/and_re/Projects/chimp-issue/node_modules/chimp/node_modules/cucumber/node_modules/meteor-promise/promise_server.js:13:37
   6076   33.0%      LazyCompile: ~result /Users/and_re/Projects/chimp-issue/node_modules/xolvio-sync-webdriverio/node_modules/meteor-promise/promise_server.js:134:25
   6075  100.0%        LazyCompile: *PromiseHandle native promise.js:94:23
   6075  100.0%          LazyCompile: ~<anonymous> native promise.js:108:27
   1783   29.3%            Stub: CallApiCallbackStub {2}

  17611    3.4%  v8::internal::Heap::IteratePromotedObjectPointers(v8::internal::HeapObject*, unsigned char*, unsigned char*, bool, void (*)(v8::internal::HeapObject**, v8::internal::HeapObject*))
...