From: dennison@telepath.com
Subject: Re: Context Switching
Date: 1999/05/12
Date: 1999-05-12T00:00:00+00:00 [thread overview]
Message-ID: <7hc2lh$513$1@nnrp1.deja.com> (raw)
In-Reply-To: 3738A31D.1013C463@mitre.org
In article <3738A31D.1013C463@mitre.org>,
"Robert I. Eachus" <eachus@mitre.org> wrote:
>
>
> 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.
The "patch" I was talking about in another posting for vxWorks on a PII
was basicly the removal of a "write back invalidate cache" instruction
(WBINVD). According to Intel, it took about 5 cycles or so on a Pentium
and 486, but takes over 2000 on a PII. Yikes!
We knew there was a problem when the same code ran *slower* on a PII-400
than on a Pentium 166...
--
T.E.D.
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prev parent reply other threads:[~1999-05-12 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 ` David C. Hoos, Sr.
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
1999-05-11 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
1999-05-10 0:00 ` delay until and GNAT - expand Roger Racine
1999-05-10 0:00 ` Joel Sherrill
1999-05-11 0:00 ` isaac buchwald
1999-05-11 0:00 ` dennison
1999-05-12 0:00 ` Robert Dewar
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` dennison
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 ` 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 ` delay until and GNAT - expand Roger Racine
[not found] ` <rracine.14.00 <rracine.15.000968A0@draper.com>
1999-05-11 0:00 ` Robert Dewar
[not found] ` <rracine.14.00 <rracine.17.0007DA28@draper.com>
1999-05-12 0:00 ` dennison
1999-05-12 0:00 ` Roger Racine
1999-05-06 0:00 ` delay until and GNAT 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
1999-05-12 0:00 ` dennison [this message]
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