ruby-core

Issue #14739 has been updated by ioquatix (Samuel Williams).


Here is a more realistic benchmark which fiber context switch is only a tiny percentage of the actual run-time.

A brief summary of the benchmark: `async-http` uses an event-driven stackful coroutine (fiber) based design. Each request allocates a fiber, and each blocking operation (i.e. read) results in `Fiber.yield`. Once the IO is ready, `Fiber#resume` is called. So, for each request being processed, we expect several calls to `Fiber.yield`. `async` is optimistic so it tries to perform the operation e.g. `read` and only yields if it results in `EWOULDBLOCK` so in some cases (especially in synthetic benchmarks) some Fiber scheduling may be elided.

```
koyoko% rvm use 2.6
Using /home/samuel/.rvm/gems/ruby-2.6.0-preview2
koyoko% ruby --version
ruby 2.6.0preview2 (2018-05-31 trunk 63539) [x86_64-linux]
koyoko% bundle exec rake wrk
Running 10s test @ http://127.0.0.1:9294/
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    63.59us   77.52us   4.53ms   98.32%
    Req/Sec    16.68k     1.07k   18.32k    74.26%
  167544 requests in 10.10s, 14.54MB read
Requests/sec:  16589.33
Transfer/sec:      1.44MB
Running 10s test @ http://127.0.0.1:9294/
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    60.85us   34.26us   1.39ms   95.82%
    Req/Sec    16.82k     0.87k   18.49k    70.00%
  167424 requests in 10.00s, 14.53MB read
Requests/sec:  16742.19
Transfer/sec:      1.45MB
Running 10s test @ http://127.0.0.1:9294/
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    62.44us   54.34us   3.81ms   97.62%
    Req/Sec    16.62k     1.00k   18.09k    67.33%
  166959 requests in 10.10s, 14.49MB read
Requests/sec:  16530.76
Transfer/sec:      1.43MB
Running 10s test @ http://127.0.0.1:9294/
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    61.89us   32.53us 687.00us   94.29%
    Req/Sec    16.54k     1.20k   18.37k    67.33%
  166105 requests in 10.10s, 14.42MB read
Requests/sec:  16445.91
Transfer/sec:      1.43MB
Running 10s test @ http://127.0.0.1:9294/
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    60.90us   37.64us   1.70ms   95.89%
    Req/Sec    16.89k     1.22k   18.57k    72.28%
  169694 requests in 10.10s, 14.73MB read
Requests/sec:  16802.33
Transfer/sec:      1.46MB
```

Here is with the PR:

```
koyoko% rvm use ruby-head-fiber
Using /home/samuel/.rvm/gems/ruby-head-fiber
koyoko% ruby --version
ruby 2.6.0dev (2018-06-01 native-fiber 63544) [x86_64-linux]
last_commit=Better support for amd64 platforms
koyoko% bundle exec rake wrk
Running 10s test @ http://127.0.0.1:9294/
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    62.53us   73.11us   5.02ms   97.96%
    Req/Sec    16.80k     1.35k   19.46k    63.37%
  168863 requests in 10.10s, 14.65MB read
Requests/sec:  16719.77
Transfer/sec:      1.45MB
Running 10s test @ http://127.0.0.1:9294/
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    58.91us   35.19us   1.54ms   95.25%
    Req/Sec    17.49k     1.16k   19.42k    69.31%
  175719 requests in 10.10s, 15.25MB read
Requests/sec:  17399.00
Transfer/sec:      1.51MB
Running 10s test @ http://127.0.0.1:9294/
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    58.64us   45.92us   3.09ms   96.88%
    Req/Sec    17.72k     1.10k   19.42k    71.29%
  178027 requests in 10.10s, 15.45MB read
Requests/sec:  17626.32
Transfer/sec:      1.53MB
Running 10s test @ http://127.0.0.1:9294/
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    60.83us   33.93us   1.06ms   94.93%
    Req/Sec    16.86k     1.54k   19.36k    63.37%
  169307 requests in 10.10s, 14.69MB read
Requests/sec:  16764.19
Transfer/sec:      1.45MB
Running 10s test @ http://127.0.0.1:9294/
  1 threads and 1 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    59.07us   39.77us   2.17ms   95.97%
    Req/Sec    17.52k     0.98k   19.32k    66.34%
  176112 requests in 10.10s, 15.28MB read
Requests/sec:  17436.64
Transfer/sec:      1.51MB
```

This is actually better than I expected. I would say there is a practical improvement of about ~5%. In this situation it's very workload dependent, but I'm glad that I saw something.

----------------------------------------
Feature #14739: Improve fiber yield/resume performance
https://bugs.ruby-lang.org/issues/14739#change-72345

* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
I am interested to improve Fiber yield/resume performance.

I've used this library before: http://software.schmorp.de/pkg/libcoro.html and handled millions of HTTP requests using it.

I'd suggest to use that library.

As this is used in many places in Ruby (e.g. enumerable) it could be a big performance win across the board.

Here is a nice summary of what was done for RethinkDB: https://rethinkdb.com/blog/making-coroutines-fast/

Does Ruby currently reuse stacks? This is also a big performance win if it's not being done already.



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