Re: [Algorithms] General purpose task parallel threading approach

[Jarkko L. <al...@gm...>]

Sub-tasks spawn by a task are not necessarily run serially by the same
worker thread though. Worker threads should pull tasks from job queue based
on task priority, so those spawned tasks are likely to be executed by many
worker threads instead.

 

 

Cheers, Jarkko

 

  _____  

From: Sebastian Sylvan [mailto:seb...@gm...] 
Sent: Sunday, April 05, 2009 3:51 AM
To: Game Development Algorithms
Subject: Re: [Algorithms] General purpose task parallel threading approach

 

Assuming I did understand you correctly, I'll just say that I think adding
(even slight) overhead to the "run" method of every single task in order to
make blocking cheaper is a big mistake. The whole motivating idea behind
task parallelism is that you saturate the system with way more runnable
tasks than there are hardware capabilities, so that performance can scale
with hardware, and that no CPU capability is left idle. If the number of
runnable tasks is much larger than the actual number of worker threads, that
means that most tasks will just run serially on the same worker that spawned
them, which means that most synchronisation points won't block, which means
that the number of thread switches will be few compared to the number of
task executions, which means that optimizing for fast blocking is not as
important as making sure that running a task is dirt cheap.


-- 
Sebastian Sylvan
+44(0)7857-300802
UIN: 44640862