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1 point by kranerup 4988 days ago | link | parent

Using pthreads might have some benefits but speed is not a reason for choosing pthreads. On Linux systems that maps pthreads onto kernel threads I've seen a two order of magnitude slower execution compared to an user space thread library. In general I'd say that if I/O is important then using pthreads would make sense but if speed is important then green threads is preferable.


2 points by stefano 4987 days ago | link

I thought pthreads were fast, but anyway on computers with more than one core/processor, which are very common, green threads don't distribute the threads between the cores, because this is the OS's duty, and it doesn't know anything about green threads.

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3 points by almkglor 4987 days ago | link

Hmm. After a bit of research, it seems that some VM's handle this by using pthreads a few times (presumably one per core), then having each pthread spawn several green threads.

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2 points by stefano 4987 days ago | link

This seems a good solution if we can arrange to spawn a new pthread also for blocking I/O, maybe by catching I/O functions and putting into a pthread the I/O operation caller. This hybrid would make the compiler code not very clean, because it should handle both green threads and pthreads.

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