State of Loom

[Magnus Ihse Bursie]

On 2020-05-26 14:16, Ron Pressler wrote:
> I meant the former, “obvious” reading. Because there are many more 
> threads,
> the footprint impact of thread-local data is bigger.
Ok, good. :-)

/Magnus
>
> — Ron
>
>
> On 26 May 2020 at 13:10:36, Magnus Ihse Bursie 
> (magnus.ihse.bursie at oracle.com <mailto:magnus.ihse.bursie at oracle.com>) 
> wrote:
>
>> Hi Ron,
>>
>> Thank you for a well-written presentation!
>>
>> I just reacted to the following statement: "ThreadLocals work for
>> virtual threads, as they do for the OS-backed threads, but as they might
>> drastically increase memory footprint". Could you possibly elaborate a
>> bit on why this would be?
>>
>> What is "drastically" here? Do you mean that like "if you have a million
>> threads, then you will have a million copies of the thread local data in
>> question"? That sounds like a very obvious result of combining huge
>> number of threads with thread local data. If you have a fantazillion
>> number of threads, then of course you are going to need a fantazillion
>> number of stack local variables, so reasonably you will also need a
>> fantazillion number of thread local variables.
>>
>> Or do you mean that Loom will consume significantly *more* memory than
>> N*sizeof(ThreadLocal data) for N threads? If so, why is that?
>>
>> /Magnus
>>
>> On 2020-05-15 16:55, Ron Pressler wrote:
>> > Hello.
>> >
>> > I’ve posted a document describing the project’s goals and current 
>> progress:
>> >
>> >   http://cr.openjdk.java.net/~rpressler/loom/loom/sol1_part1.html
>> >
>> > It is accompanied by a new EA build, based on jdk-15+21.
>> >
>> >     http://jdk.java.net/loom/
>> >
>> > The new continuations algorithm is now switched on by default, so 
>> if you haven’t
>> > explicitly turned it on before, you may see some performance 
>> improvements.
>> > You can switch it off with -XX:-UseContinuationChunks.
>> >
>> > — Ron
>> >
>> >
>> >
>>