[concurrency-interest] On park and unpark

Andrew Haley aph at redhat.com
Sun Aug 27 03:08:28 EDT 2017


On 26/08/17 23:56, David Holmes wrote:
>> On 25/08/17 23:29, David Holmes wrote:
>>
>>> We've been trying to consolidate and share as much common code as
>>> possible on "posix" supporting platforms and recently refactored
>>> things to share the PlatformEvent and Parker code (8174231). So to
>>> me there would have to be a big win in using futex directly to
>>> justify using a custom implementation.

>> That seems rather surprising to me: HotSpot has always allowed
>> (nay, even encouraged) back ends to use custom code for performance
>> reasons, and has never insisted that there must be a "big win".  At
>> least as long as I can remember.  If there's been a change of
>> policy in this area it should be up for discussion.

> To me "performance reasons" == "big win". You don't introduce
> specialized, harder to maintain, platform specific code, unless
> there is a good reason to. I don't think there has been any "change
> in policy" here - not that there has really been a "policy" as such.

Okay, but "big win" is IMO raising the bar much too high.  Efficient
systems are composed of thousands of tiny incremental improvements,
each one of which may be too small to measure on its own.

-- 
Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
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