From: Ralf Baechle <ralf@oss.sgi.com>
To: Justin Carlson <justinca@ri.cmu.edu>
Cc: Daniel Jacobowitz <dan@debian.org>, "H . J . Lu" <hjl@lucon.org>,
"Maciej W. Rozycki" <macro@ds2.pg.gda.pl>,
Hiroyuki Machida <machida@sm.sony.co.jp>,
libc-alpha@sources.redhat.com, linux-mips@oss.sgi.com
Subject: Re: PATCH: Fix ll/sc for mips (take 3)
Date: Mon, 4 Feb 2002 07:46:19 +0100 [thread overview]
Message-ID: <20020204074619.B13799@dea.linux-mips.net> (raw)
In-Reply-To: <1012676003.1563.6.camel@xyzzy.stargate.net>; from justinca@ri.cmu.edu on Sat, Feb 02, 2002 at 01:53:23PM -0500
On Sat, Feb 02, 2002 at 01:53:23PM -0500, Justin Carlson wrote:
> 2) More importantly, most implementations don't use any sort of dynamic
> branch prediction on branch likelies. They predict taken, always, since
> that's the specified intent (it's a branch *likely* to be taken).
CPU guys hate branch likely and would probably love if whoever invented
them hires at Intel ;-)
> For most spin locks, the normal behaviour is a fall through, not taking
> that branch, so you're inflicting a branch mispredict penalty on every
> lock grabbed without contention. Even for locks which the general case
> is contention, giving the processor branch predictor a chance to learn
> that is a Good Idea.
I was thinking about spinlocks like
retry: la addrreg, retry
ll reg, lockvar
...
sc reg, lockvar
teq $0, reg
That would depend on the price of a trap instruction when it's not taken
and the probability of the lock being congested.
Ralf
next prev parent reply other threads:[~2002-02-04 13:20 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-31 20:35 PATCH: Fix ll/sc for mips H . J . Lu
2002-01-31 22:17 ` Maciej W. Rozycki
2002-01-31 22:41 ` H . J . Lu
2002-02-01 3:35 ` Hiroyuki Machida
2002-02-01 4:02 ` [libc-alpha] " Kaz Kylheku
2002-02-01 4:02 ` Kaz Kylheku
2002-02-01 4:59 ` Hiroyuki Machida
2002-02-01 7:00 ` H . J . Lu
2002-02-01 11:12 ` Hiroyuki Machida
2002-02-01 10:49 ` Andreas Schwab
2002-02-01 11:23 ` Geoff Keating
2002-02-01 7:10 ` H . J . Lu
2002-02-01 7:17 ` H . J . Lu
2002-02-01 11:45 ` Maciej W. Rozycki
2002-02-01 18:29 ` PATCH: Fix ll/sc for mips (take 3) H . J . Lu
2002-02-01 23:01 ` Daniel Jacobowitz
2002-02-01 23:15 ` H . J . Lu
2002-02-02 2:37 ` Hiroyuki Machida
2002-02-04 9:32 ` Dominic Sweetman
2002-02-05 6:16 ` Jay Carlson
2002-02-05 8:28 ` Ralf Baechle
2002-02-05 15:10 ` Jay Carlson
2002-02-05 16:06 ` Jay Carlson
2002-02-02 3:26 ` Daniel Jacobowitz
2002-02-02 18:53 ` Justin Carlson
2002-02-02 20:03 ` H . J . Lu
2002-02-02 20:49 ` Hartvig Ekner
2002-02-02 20:49 ` Hartvig Ekner
2002-02-03 5:47 ` Justin Carlson
2002-02-04 19:17 ` Paul Koning
[not found] ` <mailpost.1012680250.7159@news-sj1-1>
2002-02-03 23:29 ` cgd
2002-02-04 6:07 ` Ralf Baechle
2002-02-04 9:46 ` Dominic Sweetman
2002-02-04 16:31 ` H . J . Lu
2002-02-04 16:46 ` Dominic Sweetman
2002-02-05 1:28 ` H . J . Lu
2002-02-05 2:58 ` Daniel Jacobowitz
2002-02-05 4:42 ` H . J . Lu
2002-02-05 4:47 ` Daniel Jacobowitz
2002-02-05 5:30 ` Justin Carlson
2002-02-05 8:39 ` Hartvig Ekner
2002-02-05 8:39 ` Hartvig Ekner
2002-02-05 11:37 ` Maciej W. Rozycki
2002-02-05 12:12 ` Ralf Baechle
2002-02-05 12:31 ` Maciej W. Rozycki
2002-02-05 12:38 ` Hartvig Ekner
2002-02-05 12:38 ` Hartvig Ekner
2002-02-05 13:28 ` Maciej W. Rozycki
2002-02-05 19:28 ` Hartvig Ekner
2002-02-05 19:28 ` Hartvig Ekner
2002-02-05 18:59 ` Ralf Baechle
2002-02-05 19:30 ` H . J . Lu
2002-02-05 21:54 ` H . J . Lu
2002-02-06 10:32 ` Ralf Baechle
2002-02-06 20:45 ` Why does -g turn off filling the delat slot? H . J . Lu
2002-02-06 21:00 ` PATCH: Modify the mips gas behavior for -g -O H . J . Lu
2002-02-06 21:16 ` Eric Christopher
2002-02-06 21:40 ` Ian Lance Taylor
2002-02-06 21:46 ` Eric Christopher
2002-02-06 22:00 ` PATCH: Define SUBTARGET_ASM_DEBUGGING_SPEC for Linux/mips H . J . Lu
2002-02-07 8:24 ` Eric Christopher
2002-02-06 11:37 ` PATCH: Fix ll/sc for mips (take 3) Maciej W. Rozycki
2002-02-04 17:44 ` cgd
2002-02-04 6:46 ` Ralf Baechle [this message]
2002-02-04 7:01 ` PATCH: Fix ll/sc for mips Ralf Baechle
2002-02-04 14:54 ` Maciej W. Rozycki
2002-02-01 11:50 ` Maciej W. Rozycki
2002-02-01 17:40 ` H . J . Lu
2002-02-01 21:41 ` Maciej W. Rozycki
2002-02-01 22:47 ` H . J . Lu
2002-02-02 11:06 ` Maciej W. Rozycki
2002-02-03 2:29 ` Ulrich Drepper
2002-02-03 2:29 ` Ulrich Drepper
2002-01-31 23:33 ` [libc-alpha] " Kaz Kylheku
2002-01-31 23:33 ` Kaz Kylheku
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