Issue #14723 has been updated by sam.saffron (Sam Saffron).


I found one place where we were not using async_exec so I changed it to use async_exec... this is revised numbers:


Pre patch:

```
categories:
  50: 53
  75: 59
  90: 63
  99: 76
home:
  50: 57
  75: 64
  90: 68
  99: 136
topic:
  50: 58
  75: 61
  90: 68
  99: 110
categories_admin:
  50: 96
  75: 102
  90: 108
  99: 184
home_admin:
  50: 104
  75: 112
  90: 122
  99: 213
topic_admin:
  50: 115
  75: 121
  90: 139
  99: 184
timings:
  load_rails: 4936
ruby-version: 2.6.0-p-1
rss_kb: 193500
pss_kb: 134214
memorysize: 7.79 GB
virtual: vmware
architecture: amd64
operatingsystem: Ubuntu
processor0: Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz
physicalprocessorcount: 2
kernelversion: 4.15.0
rss_kb_21961: 305616
pss_kb_21961: 243099
rss_kb_22009: 304644
pss_kb_22009: 241972
rss_kb_22133: 304108
pss_kb_22133: 241388
```


Post patch:

```
Your Results: (note for timings- percentile is first, duration is second in millisecs)
Unicorn: (workers: 3)
Include env: false
Iterations: 200, Best of: 1
Concurrency: 1

---
categories:
  50: 54
  75: 59
  90: 66
  99: 84
home:
  50: 57
  75: 62
  90: 65
  99: 139
topic:
  50: 56
  75: 61
  90: 67
  99: 104
categories_admin:
  50: 95
  75: 99
  90: 106
  99: 179
home_admin:
  50: 99
  75: 103
  90: 106
  99: 195
topic_admin:
  50: 109
  75: 114
  90: 118
  99: 163
timings:
  load_rails: 4851
ruby-version: 2.6.0-p-1
rss_kb: 195164
pss_kb: 136384
memorysize: 7.79 GB
virtual: vmware
architecture: amd64
operatingsystem: Ubuntu
processor0: Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz
physicalprocessorcount: 2
kernelversion: 4.15.0
rss_kb_19222: 305328
pss_kb_19222: 243213
rss_kb_19267: 303188
pss_kb_19267: 240952
rss_kb_19384: 307992
pss_kb_19384: 245778
```

perf change seems a tiny bit more noticable. 

----------------------------------------
Feature #14723: [WIP] sleepy GC
https://bugs.ruby-lang.org/issues/14723#change-71825

* Author: normalperson (Eric Wong)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
The idea is to use "idle time" when process is otherwise sleeping
and using no CPU time to perform GC.  It makes sense because real
world traffic sees idle time due to network latency and waiting
for user input.

Right now, it's Linux-only.  Future patches will affect other sleeping
functions:

  IO.select, Kernel#sleep, Thread#join, Process.waitpid, etc...

I don't know if this patch can be implemented for win32, right
now it's just dummy functions and that will be somebody elses
job.  But all pthreads platforms should eventually benefit.


Before this patch, the entropy-dependent script below takes 95MB
consistently on my system.  Now, depending on the amount of
entropy on my system, it takes anywhere from 43MB to 75MB.

I'm using /dev/urandom to simulate real-world network latency
variations.  There is no improvement when using /dev/zero
because the process is never idle.

  require 'net/http'
  require 'digest/md5'
  Thread.abort_on_exception = true
  s = TCPServer.new('127.0.0.1', 0)
  len = 1024 * 1024 * 1024
  th = Thread.new do
    c = s.accept
    c.readpartial(16384)
    c.write("HTTP/1.0 200 OK\r\nContent-Length: #{len}\r\n\r\n")
    IO.copy_stream('/dev/urandom', c, len)
    c.close
  end

  addr = s.addr
  Net::HTTP.start(addr[3], addr[1]) do |http|
    http.request_get('/') do |res|
      dig = Digest::MD5.new
      res.read_body { |buf|
        dig.update(buf)
      }
      puts dig.hexdigest
    end
  end

The above script is also dependent on net/protocol using
read_nonblock.  Ordinary IO objects will need IO#nonblock=true
to see benefits (because they never hit rb_wait_for_single_fd)

* gc.c (rb_gc_inprogress): new function
  (rb_gc_step): ditto
* internal.h: declare prototypes for new gc.c functions
* thread_pthread.c (gvl_contended_p): new function
* thread_win32.c (gvl_contended_p): ditto (dummy)
* thread.c (rb_wait_for_single_fd w/ ppoll):
  use new functions to perform GC while GVL is uncontended
  and GC is lazy sweeping or incremental marking
  [ruby-core:86265]
```

2 part patch broken out
https://80x24.org/spew/20180429035007.6499-2-e / 80x24.org/raw
https://80x24.org/spew/20180429035007.6499-3-e / 80x24.org/raw

Also on my "sleepy-gc" git branch @ git://80x24.org/ruby.git


---Files--------------------------------
sleepy-gc-wip-v1.diff (5.37 KB)


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