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Date:      Mon, 7 Dec 1998 19:59:07 -0000 
From:      James Mansion <james@westongold.com>
To:        Gary Palmer <gpalmer@FreeBSD.ORG>, Michael Galassi <nerd@xyz.com>
Cc:        Marcel van Kervinck <marcelk@stack.nl>, smp@FreeBSD.ORG
Subject:   RE: Pthreads and SMP 
Message-ID:  <32BABEF63EAED111B2C5204C4F4F50201835@WGP01>

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I think what you wrote is not representative in many cases.  Its
not representative of ANY of my threaded development.

I normally expect (and desire) threads to be spread over the
system's CPUs.

If I want to do a lot of IO, I'd rather set it up as aio_ or lio_
calls.  Running a thread per client is very dangerous unless
you KNOW that you will only run on systems that have an N:1
(ugh!) or M:N structure.  Its not guaranteed by POSIX at all.

While its clear that working on a hot structure from multiple
threads can give your caches headaches, its by far the best
way to handle concurrent queries against general data structures.

Reducing contention is clearly a design issue of threaded
development.

It does seem that FreeBSD is some way from being leading edge
as a platform for threaded or AIO applications - hopefully this
will only be a temporary thing.

James

> -----Original Message-----
> From: Gary Palmer [mailto:gpalmer@FreeBSD.ORG]
...
> Seriously, there are advantages to thread migration and 
> disadvantages. I 
> believe Solaris only does thread migration when the CPU that 
> the process is on 
> is overcomitted. So unless you were totally CPU bound (in 
> which case the 
> process shouldn't have been threaded anyhow, as threads get 
> their advantage 
> from being I/O or network bound), there shouldn't really be a 
> problem...

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