On Fri, 07 Apr 2000, you wrote:
> On Fri, 7 Apr 2000, Ian C.Sison wrote:
> ..
> > U-uh, I don't agree. First of all threads on linux is a misnomer
> > because it isn't supported by the kernel. A kludge is done to make it
> > seem to be a thread but it is actually a fork in disguise.
>
> It's functionally a thread, and its good enough for MySQL which is one of
> the most demanding threaded applications out there.
>
> The reason threads are implemented as processes in Linux is to avoid extra
> LWP overhead and to allow threads to be seamlessly distributed over
> processors.
There was an article i read once that mentioned the fact that distributing
threaded code over several processors actually degrades performance rather than
improves it. Reason? Context switching between threads and processors breaks
the caches of the CPUs enough to provide a noticable performance hit. So much
so, that you'ld be better off with a uniprocessor box.
> The context-switch latency on Linux is much less than on other
> OS's (see McVoy's lmbench) so there is no time savings in avoiding the
> fork, unlike say Solaris where a thread switch takes 1/100th the time of a
> full context switch.
I'm not sure about this one, and neither do i have benchmark results proving
that the assertion i read was really true. \8)
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