5x Slower Context Switching Between Fiber-vs-Thread

[Remi Forax]

Hi Volkan,
i will take a look this evening.

Rémi

----- Mail original -----
> De: "Volkan Yazıcı" <volkan.yazici at gmail.com>
> À: "Alan Bateman" <Alan.Bateman at oracle.com>
> Cc: "loom-dev" <loom-dev at openjdk.java.net>
> Envoyé: Mardi 5 Février 2019 09:41:17
> Objet: Re: 5x Slower Context Switching Between Fiber-vs-Thread

> It was my pleasure to meet with you all.
> I have created a GiST:
> https://gist.github.com/vy/c5031a54d42f9e5b855463c838fed6a9
> You can just run the file as follows: *java SlowFiberReport.java*
> 
> On Tue, Feb 5, 2019 at 9:33 AM Alan Bateman <Alan.Bateman at oracle.com> wrote:
> 
>> Nice to meet you at FOSDEM and the OCW.
>>
>> Can you send me the benchmark, I think the attachment is being stripped
>> by the mail servers.
>>
>> -Alan
>>
>> On 04/02/2019 21:16, Volkan Yazıcı wrote:
>> > Hello,
>> >
>> > In the attached SlowFiberReport.java, main() calls runThreads() and
>> > runFibers() methods and measures the total time it takes. The former,
>> > runThreads(), creates 50 threads and passes a token sequentially 1e6
>> times.
>> > Whereas the latter, runFibers(), creates 50 fibers running on a
>> > single-threaded scheduler and again passes a token sequentially 1e6
>> times.
>> > For synchronization purposes, both approaches use a dedicated Lock and
>> > Condition pair for each thread and fiber, respectively. While I am aware
>> > that it is still early to assess the performance of Loom, I am surprised
>> to
>> > see threads performing ~5x better (6s-vs-30s) compared to fibers in terms
>> > of basic unmount/mount costs. Would anybody mind helping me to understand
>> > the cause of the slowness, please? (I hope I am not doing something brain
>> > dead.)
>> >
>> > Best.
>> >
>> > *Note:* Using a JDK compiled from 2019-01-20 sources.
>>