From: Cort Dougan <cort@fsmlabs.com>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Why Plan 9 C compilers don't have asm("")
Date: Fri, 6 Jul 2001 02:38:35 -0600 [thread overview]
Message-ID: <20010706023835.A5224@ftsoj.fsmlabs.com> (raw)
In-Reply-To: <200107040337.XAA00376@smarty.smart.net> <20010703233605.A1244@zalem.puupuu.org> <20010704002436.C1294@ftsoj.fsmlabs.com> <9hvjd4$1ok$1@penguin.transmeta.com>
In-Reply-To: <9hvjd4$1ok$1@penguin.transmeta.com>; from torvalds@transmeta.com on Wed, Jul 04, 2001 at 05:22:44PM +0000
I'm talking about _modern_ processors, not processors that dominate the
modern age. This isn't x86. I don't believe that even aggressive
re-ordering will cause a serious hit in performance on function calls.
Unconditional branches are definitely predictable so icache pre-fetches are
not more complicated that straight-line code.
Measurement is more important, though. I've rejected a number of
optimizations from people (including many of my own) that were "obvious
enhancements" because of what they showed in real-world measurements. If
it doesn't run faster, despite the theory being "right", it's worthless.
next prev parent reply other threads:[~2001-07-06 8:38 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-07-04 3:37 Why Plan 9 C compilers don't have asm("") Rick Hohensee
2001-07-04 3:36 ` Olivier Galibert
2001-07-04 6:24 ` Cort Dougan
2001-07-04 8:03 ` H. Peter Anvin
2001-07-04 17:22 ` Linus Torvalds
2001-07-06 8:38 ` Cort Dougan [this message]
2001-07-06 11:43 ` David S. Miller
2001-07-06 18:44 ` Linus Torvalds
2001-07-06 20:02 ` Cort Dougan
2001-07-08 21:55 ` Victor Yodaiken
2001-07-08 22:28 ` Alan Cox
2001-07-08 22:29 ` David S. Miller
2001-07-09 1:22 ` Johan Kullstam
2001-07-21 22:10 ` Richard Henderson
2001-07-22 3:43 ` Linus Torvalds
2001-07-22 3:59 ` Mike Castle
2001-07-22 6:49 ` Richard Henderson
2001-07-22 7:44 ` Linus Torvalds
2001-07-22 15:53 ` Richard Henderson
2001-07-22 19:08 ` Linus Torvalds
2001-07-04 7:15 ` pazke
2001-07-04 17:32 ` Don't feed the trooll [offtopic] " Ben LaHaise
2001-07-05 1:02 ` Michael Meissner
2001-07-05 1:54 ` Rick Hohensee
2001-07-05 16:54 ` Michael Meissner
-- strict thread matches above, loose matches on Subject: below --
2001-07-04 10:10 Rick Hohensee
2001-07-05 3:26 Rick Hohensee
2001-07-06 17:24 Rick Hohensee
2001-07-06 23:54 ` David S. Miller
2001-07-07 0:16 ` H. Peter Anvin
2001-07-07 0:37 ` David S. Miller
2001-07-07 6:16 Rick Hohensee
[not found] <mailman.994629840.17424.linux-kernel2news@redhat.com>
2001-07-09 0:08 ` Pete Zaitcev
2001-07-09 0:28 ` Victor Yodaiken
2001-07-09 3:03 Rick Hohensee
2001-07-23 4:39 Rick Hohensee
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