[dart:io] Re-limit the number of IO Service ports per Isolate

[dart:io] Re-limit the number of IO Service ports per Isolate

Previous change removed the limit, but this causes too many
threads to be spawned at the same time on Windows, which
crashes the VM. This change restores the limit, but continues
use of the free-list approach, which still avoids the blocking
problem fixed by the previous change.

fixes #29702

R=rmacnak@google.com

Committed: https://github.com/dart-lang/sdk/commit/61300d19c60851fb306656d97e5bea42dcfe0aa8

[zra, 2017-05-24 15:11:15]

Description was changed from

==========
[dart:io] Re-limit the number of IO Service ports per Isolate
==========

to

==========
[dart:io] Re-limit the number of IO Service ports per Isolate

Previous change removed the limit, but this causes too many
threads to be spawned at the same time on Windows, which
crashes the VM. This change restores the limit, but continues
use of the free-list approach, which still avoids the blocking
problem fixed by the previous change.

fixes #29702
==========

[zra, 2017-05-24 15:11:31]

zra@google.com changed reviewers:
+ asiva@google.com, bkonyi@google.com

[zra, 2017-05-24 17:12:25]

zra@google.com changed reviewers:
+ rmacnak@google.com

[rmacnak, 2017-05-24 17:18:39]

lgtm

[zra, 2017-05-24 17:22:29]

Description was changed from

==========
[dart:io] Re-limit the number of IO Service ports per Isolate

Previous change removed the limit, but this causes too many
threads to be spawned at the same time on Windows, which
crashes the VM. This change restores the limit, but continues
use of the free-list approach, which still avoids the blocking
problem fixed by the previous change.

fixes #29702
==========

to

==========
[dart:io] Re-limit the number of IO Service ports per Isolate

Previous change removed the limit, but this causes too many
threads to be spawned at the same time on Windows, which
crashes the VM. This change restores the limit, but continues
use of the free-list approach, which still avoids the blocking
problem fixed by the previous change.

fixes #29702

R=rmacnak@google.com

Committed:
https://github.com/dart-lang/sdk/commit/61300d19c60851fb306656d97e5bea42dcfe0aa8
==========

[zra, 2017-05-24 17:22:31]

Committed patchset #1 (id:1) manually as
61300d19c60851fb306656d97e5bea42dcfe0aa8 (presubmit successful).

[bkonyi, 2017-05-24 17:49:09]

Just curious, but is there any situation where we would need more than 32 IO
service ports active at the same time? If so, how are we handling that?

[zra, 2017-05-24 18:00:16]

On 2017/05/24 17:49:09, bkonyi wrote:
> Just curious, but is there any situation where we would need more than 32 IO
> service ports active at the same time? If so, how are we handling that?

The 33d request could potentially be starved if there are 32 long-blocking
requests in progress. However, since we can't create an arbitrary number of
threads/ports, we have to pick *some* number where that will happen. It could be
the case that 32 is too small, so we'll just have to see how things go.