On Fri, 15 Mar 2002, Malcolm Kavalsky wrote:
> I have been following this "thread" for a while, and feel impelled to
> comment:
>
> "Don't use threads !"
>
This is the standard "Use qmail instead" reply to "I want to do this with
sendmail". Perhaps pertinent, but not what the one who asked the question
wishes to hear.
I won't comment further, but I'll just say that some of the problems one
encounters with multi-threading exist in one form or another in
multi-processing. Furthermore, multi-threading waiting for
synchronizations can be avoided by using trylock and friends. This will
require a more complicated design, but is doable. (and there are many
times similar phenomena in multi-processing).
I heard an anti-threads rant from a different source, too. However, most
people find problem solving using threads much easier than
multi-processing games, regardless from which OSes they came from. So,
like it or not multi-threading is here to stay.
Regards,
Shlomi Fish
> Linux has a very efficient process model and if you are writing any
> reasonable
> size program and don't want to get into trouble, then I suggest you
> split it into
> multiple processes and use IPC.
>
> In my 20 years of programming experience, there are very few cases which I
> have come across that warrant the use of threads.
>
> The initial appeal of using threads (easy sharing of global data structures,
> concurrent programming, low overhead task switching) is quickly dispelled
> the minute you start wondering why your program is crashing/dead-locking.
> After adding in lots of mutexes to protect all your data structures,
> your program
> slows to a crawl, and tracing it reveals that 99% of the time is spent
> in lock/unlock
> calls. Note also that C++ has certain effects that make use of threads
> dangerous and
> any library calls that you use automatically, need to be checked that
> they are MT-safe.
>
> Using processes on the other hand, usually ensures that each task truly
> runs in parallel
> and the OS protects each task from the other. You need to work a little
> harder in the
> beginning to setup the IPC, but once that is done, you are home free,
> and can more easily
> debug your application (each process individually, deterministically).
> IPC ensures that
> only data that you want to be shared will be, and only when you want it
> to be. Note also
> that C++ has certain effects that make use of threads dangerous. Any
> library calls that
> you use automatically, need to be checked that they are MT-safe, even
> the most harmless.
>
> Most windows programmers that I have met, are used to working with
> threads, and it
> is hard to change their habits to use processes. Also, realtime
> programmers often are also
> used to threads since originally most realtime OSes didn't support
> processes, and if they
> did then the context switches were too high. Linux, on the other hand,
> has an excellent
> low-overhead process model which removes 99% of the reason to use threads.
>
> Ousterhout wrote a seminal article titled "Why threads are bad" which
> goes into more
> detail ( you can STW for it).
>
>
> Just my 2 cents worth ...
>
> Malcolm
>
> Shlomi Fish wrote:
>
> >On Thu, 14 Mar 2002, Nadav Har'El wrote:
> >
> >>On Thu, Mar 14, 2002, Isaac Aaron wrote about "RE: pthreads question":
> >>
> >>>The thing is, I Read the F Manual (over and over, even considered trying
> >>>mit-pthreads instead), did didn't think that I WANT to detach the thread?
> >>>(Why detach? I kind of like it... Better keep it).
> >>>
> >>That's where books are better than manuals - given their length, they can
> >>also give examples and explain the ideas behind why certain things were
> >>done the way they were done, and what they are good for.
> >>
> >
> >I believe, but am not sure, that there are good tutorials and lectures
> >online about it too. STFW.
> >
> >>The book I'd recommend is David R. Butenhof's "Programming with Posix Threads"
> >>(see e.g., http://www.amazon.com/exec/obidos/ASIN/0201633922/thealmostcomplet )
> >>If I remember correctly, Butenhof was one of the people working on the
> >>Posix threads standard, and talks a lot about the motivations of how and why
> >>to do things (it talks only on C, of course - if you're looking for OOP
> >>abstractions of threads look elsewhere; I just wrote my own).
> >>
> >
> >You can find some useful abstractions for them here:
> >
> >http://vipe.technion.ac.il/~shlomif/abstraction/ (under System-Services
> >Abstractions)
> >
> >If there's anything missing let me know. And Nadav - you should know
> >better than to invent your own wheel. ;-)
> >
> >>This is the book I learned Posix threads from.
> >>
> >
> >I learned POSIX threads from online and hard-disk resources, and from my
> >"Structure of OS" course. The pthreads API is not very hard or complex,
> >but of course preventing dead-locks, starvation and other multi-tasking
> >mishaps is something that requires a lot of though.
> >
> >Regards,
> >
> > Shlomi Fish
> >
> >>
> >>--
> >>Nadav Har'El | Thursday, Mar 14 2002, 2 Nisan 5762
> >>[EMAIL PROTECTED] |-----------------------------------------
> >>Phone: +972-53-245868, ICQ 13349191 |Why aren't fishmongers generous? Their
> >>http://nadav.harel.org.il |business makes them selfish.
> >>
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> >
> >
> >
> >----------------------------------------------------------------------
> >Shlomi Fish [EMAIL PROTECTED]
> >Home Page: http://t2.technion.ac.il/~shlomif/
> >Home E-mail: [EMAIL PROTECTED]
> >
> >"Let's suppose you have a table with 2^n cups..."
> >"Wait a second - is n a natural number?"
> >
> >
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>
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----------------------------------------------------------------------
Shlomi Fish [EMAIL PROTECTED]
Home Page: http://t2.technion.ac.il/~shlomif/
Home E-mail: [EMAIL PROTECTED]
"Let's suppose you have a table with 2^n cups..."
"Wait a second - is n a natural number?"
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