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Date: Wed, 13 Jun 2001 19:31:39 +0200
From: bert hubert <ahu@ds9a.nl>
To: linux-kernel@vger.kernel.org
Subject: Re: threading question
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In-Reply-To: <Pine.GSO.4.10.10106121200330.20809-100000@orbit-fe.eng.netapp.com>; from kmacy@netapp.com on Tue, Jun 12, 2001 at 12:06:40PM -0700
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On Tue, Jun 12, 2001 at 12:06:40PM -0700, Kip Macy wrote:
> This may sound like flamebait, but its not. Linux threads are basically
> just processes that share the same address space. Their performance is
> measurably worse than it is on most commercial Unixes and FreeBSD.

Thread creation may be a bit slow. But the kludges to provide posix threads
completely from userspace also hurt. Notably, they do not scale over
multiple CPUs.

> They are not, or at least two years ago, were not POSIX compliant
> (they behaved badly with respect to signals). The impoverished

POSIX threads are silly with respect to signals. I do almost all my
programming these days with pthreads and I find that I really do not miss
signals at all.

> from Larry McVoy's home page attributed to Alan Cox illustrates this
> reasonably well: "A computer is a state machine. Threads are for people
> who can't program state machines." Sorry for not being more helpful.

I got that response too. When I pressed kernel people for details it turns
out that they think having hundreds of runnable threads/processes (mostly
the same thing under Linux) is wasteful. The scheduler is just not optimised
for that.

Regards,

bert

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