From: "David S. Miller" <davem@redhat.com>
To: torvalds@transmeta.com
Cc: alan@lxorguk.ukuu.org.uk, bcrl@redhat.com,
marcelo@conectiva.com.br, andrea@suse.de,
linux-kernel@vger.kernel.org
Subject: Re: Locking comment on shrink_caches()
Date: Wed, 26 Sep 2001 16:26:55 -0700 (PDT) [thread overview]
Message-ID: <20010926.162655.79011481.davem@redhat.com> (raw)
In-Reply-To: <Pine.LNX.4.33.0109261003480.8327-200000@penguin.transmeta.com>
In-Reply-To: <E15mHjL-0000t8-00@the-village.bc.nu> <Pine.LNX.4.33.0109261003480.8327-200000@penguin.transmeta.com>
From: Linus Torvalds <torvalds@transmeta.com>
Date: Wed, 26 Sep 2001 10:25:18 -0700 (PDT)
On Wed, 26 Sep 2001, Alan Cox wrote:
> >
> > Your Athlons may handle exclusive cache line acquisition more
> > efficiently (due to memory subsystem performance) but it still
> > does cost something.
>
> On an exclusive line on Athlon a lock cycle is near enough free, its
> just an ordering constraint. Since the line is in E state no other bus
> master can hold a copy in cache so the atomicity is there. Ditto for newer
> Intel processors
You misunderstood the problem, I think: when the line moves from one CPU
to the other (the exclusive state moves along with it), that is
_expensive_.
Yes, this was my intended point. Please see my quoted text above and
note the "exclusive cache line acquisition" with emphasis on the word
"acquisition" meaning you don't have the cache line in E state yet.
Franks a lot,
David S. Miller
davem@redhat.com
next prev parent reply other threads:[~2001-09-26 23:28 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-09-25 17:49 Marcelo Tosatti
2001-09-25 19:57 ` David S. Miller
2001-09-25 18:40 ` Marcelo Tosatti
2001-09-25 20:40 ` Josh MacDonald
2001-09-25 19:25 ` Marcelo Tosatti
2001-09-25 20:15 ` David S. Miller
2001-09-25 19:02 ` Marcelo Tosatti
2001-09-25 20:24 ` Rik van Riel
2001-09-25 22:26 ` David S. Miller
2001-09-26 17:42 ` Ingo Molnar
2001-09-25 20:28 ` David S. Miller
2001-09-25 21:05 ` Andrew Morton
2001-09-25 21:48 ` David S. Miller
2001-09-25 20:29 ` David S. Miller
2001-09-25 21:00 ` Benjamin LaHaise
2001-09-25 22:03 ` Andrea Arcangeli
2001-09-25 21:55 ` David S. Miller
2001-09-25 22:16 ` Benjamin LaHaise
2001-09-25 22:28 ` David S. Miller
2001-09-26 16:40 ` Alan Cox
2001-09-26 17:25 ` Linus Torvalds
2001-09-26 17:40 ` Alan Cox
2001-09-26 17:44 ` Linus Torvalds
2001-09-26 18:01 ` Benjamin LaHaise
2001-09-26 18:01 ` Dave Jones
2001-09-26 20:20 ` Vojtech Pavlik
2001-09-26 20:24 ` Vojtech Pavlik
2001-09-26 17:45 ` Dave Jones
2001-09-26 17:50 ` Alan Cox
2001-09-26 17:59 ` Dave Jones
2001-09-26 18:07 ` Alan Cox
2001-09-26 18:09 ` Padraig Brady
2001-09-26 18:22 ` Dave Jones
2001-09-26 18:24 ` Linus Torvalds
2001-09-26 18:40 ` Dave Jones
2001-09-26 19:12 ` Linus Torvalds
2001-09-27 12:22 ` CPU frequency shifting "problems" Padraig Brady
2001-09-27 12:44 ` Dave Jones
2001-09-27 23:23 ` Linus Torvalds
2001-09-28 0:55 ` Alan Cox
2001-09-28 2:12 ` Stefan Smietanowski
2001-09-28 8:55 ` Jamie Lokier
2001-09-28 16:11 ` Linus Torvalds
2001-09-28 20:29 ` Eric W. Biederman
2001-09-28 22:24 ` Jamie Lokier
2001-09-26 19:04 ` Locking comment on shrink_caches() George Greer
2001-09-26 18:59 ` George Greer
2001-09-26 17:43 ` Richard Gooch
2001-09-26 18:24 ` Benjamin LaHaise
2001-09-26 18:48 ` Richard Gooch
2001-09-26 18:58 ` Davide Libenzi
2001-09-26 23:26 ` David S. Miller [this message]
2001-09-27 12:10 ` Alan Cox
2001-09-27 15:38 ` Linus Torvalds
2001-09-27 17:44 ` Ingo Molnar
2001-09-27 19:41 ` David S. Miller
2001-09-27 22:59 ` Alan Cox
2001-09-25 22:01 ` Andrea Arcangeli
2001-09-25 22:03 ` David S. Miller
2001-09-25 22:59 ` Andrea Arcangeli
2001-09-25 21:57 ` Andrea Arcangeli
2001-09-26 5:04 Dipankar Sarma
2001-09-26 5:31 ` Andrew Morton
2001-09-26 7:08 ` Dipankar Sarma
2001-09-26 16:52 ` John Hawkes
2001-09-26 6:57 ` David S. Miller
[not found] <fa.cbgmt3v.192gc8r@ifi.uio.no>
[not found] ` <fa.cd0mtbv.1aigc0v@ifi.uio.no>
[not found] ` <i1m66a5o1zc.fsf@verden.pvv.ntnu.no>
2001-09-27 1:34 ` Vojtech Pavlik
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