From: "Robert I. Eachus" <eachus@mitre.org>
Subject: Re: Context Switching
Date: 1999/05/11
Date: 1999-05-11T00:00:00+00:00 [thread overview]
Message-ID: <3738A31D.1013C463@mitre.org> (raw)
In-Reply-To: 7h9nl5$9hr$1@nnrp1.deja.com
Robert Dewar wrote:
> You have to be careful here. The raw hardware speed for a
> context switch is not what is interesting, what is interesting
> is the time for executing the COMPLETE pthread call that causes
> the context switch.
>
> For example, the actual raw hardware speed for changing a task
> priority is probably just a single store instruction, but it may
> well take hundreds or even thousands of instructions to filter
> through the necessary kernel machinery to get to the point of
> issuing that store!
Actually we have been finding on some modern microprocessors that
the (distributed) overhead of cache misses can dominate other costs. On
others, where the cache is a "physical" cache that does not have to be
invalidated,
this overhead is very small. I don't remember which chips are which
here, but there were some cases where the cache miss overhead tripled
the cost of a thread switch.
--
Robert I. Eachus
with Standard_Disclaimer;
use Standard_Disclaimer;
function Message (Text: in Clever_Ideas) return Better_Ideas is...
next prev parent reply other threads:[~1999-05-11 0:00 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-05-05 0:00 delay until and GNAT isaac buchwald
1999-05-05 0:00 ` dennison
1999-05-06 0:00 ` Buz Cory
1999-05-06 0:00 ` Robert Dewar
1999-05-06 0:00 ` delay until and GNAT - expand isaac buchwald
1999-05-07 0:00 ` Roger Racine
1999-05-08 0:00 ` dewar
1999-05-10 0:00 ` Roger Racine
1999-05-10 0:00 ` Joel Sherrill
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` dennison
1999-05-11 0:00 ` isaac buchwald
1999-05-11 0:00 ` dennison
1999-05-12 0:00 ` Robert Dewar
1999-05-10 0:00 ` Context switching (was: delay until and GNAT) Nick Roberts
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` Tarjei Tj�stheim Jensen
1999-05-11 0:00 ` David Brown
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` Robert Dewar
1999-05-10 0:00 ` delay until and GNAT - expand Roger Racine
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` dennison
1999-05-11 0:00 ` Robert Dewar
1999-05-12 0:00 ` delay until and GNAT - where to get the info isaac buchwald
1999-05-12 0:00 ` Robert Dewar
[not found] ` <rracine.14.00 <rracine.15.000968A0@draper.com>
1999-05-11 0:00 ` delay until and GNAT - expand Robert Dewar
1999-05-11 0:00 ` Roger Racine
1999-05-12 0:00 ` Roger Racine
[not found] ` <rracine.14.00 <rracine.17.0007DA28@draper.com>
1999-05-12 0:00 ` dennison
1999-05-05 0:00 ` delay until and GNAT David C. Hoos, Sr.
1999-05-06 0:00 ` Roger Racine
1999-05-10 0:00 ` Nick Roberts
1999-05-11 0:00 ` Context Switching Nick Roberts
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` Robert I. Eachus [this message]
1999-05-12 0:00 ` dennison
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