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Date: Mon, 23 Sep 2002 06:05:18 -0400 (EDT)
From: Bill Davidsen <davidsen@tmr.com>
To: Larry McVoy <lm@bitmover.com>
cc: Peter Waechtler <pwaechtler@mac.com>, linux-kernel@vger.kernel.org,
       ingo Molnar <mingo@redhat.com>
Subject: Re: [ANNOUNCE] Native POSIX Thread Library 0.1
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On Sun, 22 Sep 2002, Larry McVoy wrote:

> On Sun, Sep 22, 2002 at 08:55:39PM +0200, Peter Waechtler wrote:
> > AIX and Irix deploy M:N - I guess for a good reason: it's more
> > flexible and combine both approaches with easy runtime tuning if
> > the app happens to run on SMP (the uncommon case).
> 
> No, AIX and IRIX do it that way because their processes are so bloated
> that it would be unthinkable to do a 1:1 model.

And BSD? And Solaris?
 
> Instead of taking the traditional "we've screwed up the normal system 
> primitives so we'll event new lightweight ones" try this:
> 
> We depend on the system primitives to not be broken or slow.
> 
> If that's a true statement, and in Linux it tends to be far more true
> than other operating systems, then there is no reason to have M:N.

No matter how fast you do context switch in and out of kernel and a sched
to see what runs next, it can't be done as fast as it can be avoided.
Being N:M doesn't mean all implementations must be faster, just that doing
it all in user mode CAN be faster.

Benchmarks are nice, I await results from a loaded production threaded
DNS/mail/web/news/database server. Well, I guess production and 2.5 don't
really go together, do they, but maybe some experimental site which could
use 2.5 long enough to get numbers. If you could get a threaded database
to run, that would be a good test of shared resources rather than a bunch
of independent activities doing i/o. 

-- 
bill davidsen <davidsen@tmr.com>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.

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