Talk:Thread (computing)

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Untitled

Thanks for fleshing out the stub, Lee. I knew this stuff, but it wasn't on the tip of my tongue (one step further buried in the memory banks). User:Ed Poor

Renaming

Just for note. I renamed the article to thread (computer science) because threading not necessarily only in software enginnering. -- Taku 16:14, Mar 28, 2004 (UTC)

Process creation cost

From the article:

"Systems like Windows NT, OS/2 and Linux (2.5 kernel or higher) are said to have "cheap" threads and "expensive" processes, while in other systems there is not so big a difference."

Eh? I though one major advantage of Linux was its relatively low process creation cost, and the new NPTL implementation of Linux threads is a 1:1 implementation where there is little difference between a thread and a process at the lowest level. -- The Anome 22:33, 22 Oct 2004 (UTC)

If you take a look at NetBSD 2.x or DragonFly BSD you will notice that they don't use 1:1, but instead N:M, which is a lot more efficient than Linux 1:1. I've added a link about NetBSD SA (Scheduler Activations) in this page that I advise you to look at. -- RuiPaulo 23:54, 24 Oct 2004 (UTC)

Authors

The section titled "Processes, Threads, and Fibers" and its subsections were started by Daniel Barbalace.

Website: http://www.clearthought.info

Thanks for the excellent work, Daniel. -- The Anome 14:59, 24 Oct 2004 (UTC)

System call for a context switch?

The article says "Typically fibers are implemented entirely in userspace. As a result, context switching between fibers in a process is extremely efficient: because the kernel is oblivious to the existence of fibers, a context switch does not require a system call." Why would a context switch require a system call in any situation? Is it talking about non-preemptive multitasking? If so, wouldn't it be better if the article mentioned it? If the article isn't intended to say that a system call is required for a context switch, then it would be better if it were cleared up in the article. It's misleading. It would help if the article (that section) is clearer anyway.

Yeah, it would be more clear to say "a context switch does not require a kernel entry" or some such. I'm not sure that it matters whether or not the thread implementation is preemptively scheduled or not: in a cooperatively scheduled implementation of kernel threads, there is still some kernel state associated with the currently-running thread, and so a kernel entry is some kind is required to switch that state, right? The point is somewhat academic, anyway, as cooperatively-scheduled kernel thread implementations are rare AFAIK. Neilc 04:23, 20 Jun 2005 (UTC)

I made that change. I was trying to figure out how to get something about pre-emptive scheduling of threads involving the kernel programming a hardware interrupt in order to stop the current thread, but couldn't figure out how to word that decently. :) Dianne Hackborn 05:51, 22 Jun 2005 (UTC)

Books

I've added Three .NET threading resources - two of these are admittedly my own published works. I've added them only because there were no other .NET programming resources listed. Feel free to remove them if you feel they are inappropriate. Both of these books are out of print but you can still find them quite often at book stores and from secondary book stores. I have a fourth book published that is still on the market that I didn't list because it covers two other areas as well as threading. The title is Pro .Net 1. 1 Remoting, Reflection, and Threading and the ISBN is 1-590-59452-5. While it is more "current", the fact that it covers two other topics doesn't seem to make it appropriate for this article. Once again, feel free to add it if you feel otherwise. - Sleepnomore 15:46, August 26, 2005 (UTC)

Kernel changes for M:N threading

In Thread (computing)#M:N (hybrid threading), somebody asked for a citation in this edit, with the reason being that "no kernel modifications are needed".

I changed that to a request for clarification, because that section says

M:N maps some M number of application threads onto some N number of kernel entities, or "virtual processors."

and, if your kernel has no such kernel entities that can be used, clearly implementing M:N threading will require kernel changes. However, if, for example, it already has such entities - perhaps using them for 1:1 threading - it may be possible to implement M:N threading on top of those entities, with only changes to the userland threading library.

So, if the discussions of the various threading models, the implementation complexity refers to the complexity of implementing the threading model atop a system with no support for threading, whether in the kernel or in userland, M:N threading involves changes in both cases, whereas 1:1 would require kernel changes but would probably only require relatively simple userland changes to use the new kernel facilities, rather than requiring the userland scheduling atop the kernel changes that M:N threading would require, and N:1 threading would require just a userland threading library and maybe some limited kernel mechanisms, such as a "wait for multiple events" call, if not already present. Guy Harris (talk) 15:54, 12 June 2020 (UTC)