From: Benjamin LaHaise <bcrl@redhat.com>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
"David S. Miller" <davem@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 14:01:49 -0400 [thread overview]
Message-ID: <20010926140149.C8223@redhat.com> (raw)
In-Reply-To: <E15mIfQ-0001E5-00@the-village.bc.nu> <Pine.LNX.4.33.0109261036260.8445-100000@penguin.transmeta.com>
In-Reply-To: <Pine.LNX.4.33.0109261036260.8445-100000@penguin.transmeta.com>; from torvalds@transmeta.com on Wed, Sep 26, 2001 at 10:44:14AM -0700
On Wed, Sep 26, 2001 at 10:44:14AM -0700, Linus Torvalds wrote:
> Do you have an actual SMP Athlon to test? I'd love to see if that "locked
> add" thing is really SMP-safe - it may be that it's the old "AMD turned
> off the 'lock' prefix synchronization because it doesn't matter in UP".
> They used to have a bit to do that..
Same, my dual reports:
[bcrl@toomuch ~]$ ./a.out
nothing: 11 cycles
locked add: 11 cycles
cpuid: 68 cycles
Which is pretty good.
> That said, it _can_ be real even on SMP. There's no reason why a memory
> barrier would have to be as heavy as it is on some machines (even the P4
> looks positively _fast_ compared to most older machines that did memory
> barriers on the bus and took hundreds of much slower cycles to do it).
I had discussions with a few people from intel about the p4 having much
improved locking performance, including the ability to speculatively
execute locked instructions. How much of that is enabled in the current
cores is another question entirely (gotta love microcode patches).
-ben
next prev parent reply other threads:[~2001-09-26 18:03 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-09-25 17:49 Locking comment on shrink_caches() Marcelo Tosatti
2001-09-25 19:57 ` David S. Miller
2001-09-25 18:40 ` Marcelo Tosatti
2001-09-25 20:15 ` David S. Miller
2001-09-25 19:02 ` Marcelo Tosatti
2001-09-25 20:29 ` David S. Miller
2001-09-25 21:00 ` Benjamin LaHaise
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 [this message]
2001-09-26 18:01 ` Dave Jones
2001-09-26 20:20 ` Vojtech Pavlik
2001-09-26 20:24 ` Vojtech Pavlik
2001-09-26 17:43 ` 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 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 23:26 ` David S. Miller
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 22:03 ` Andrea Arcangeli
2001-09-25 20:24 ` Rik van Riel
2001-09-25 20:28 ` David S. Miller
2001-09-25 21:05 ` Andrew Morton
2001-09-25 21:48 ` David S. Miller
[not found] ` <200109252215.f8PMFDa02034@eng2.beaverton.ibm.com>
2001-09-25 22:26 ` David S. Miller
2001-09-26 17:42 ` Ingo Molnar
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 20:40 ` Josh MacDonald
2001-09-25 19:25 ` Marcelo Tosatti
2001-09-25 21:57 ` Andrea Arcangeli
-- strict thread matches above, loose matches on Subject: below --
2001-09-26 5:04 Dipankar Sarma
2001-09-26 5:31 ` Andrew Morton
2001-09-26 6:57 ` David S. Miller
2001-09-26 7:08 ` Dipankar Sarma
2001-09-26 16:52 ` John Hawkes
[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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