From: Ingo Molnar <mingo@elte.hu>
To: Andi Kleen <andi@firstfloor.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andi Kleen <ak@suse.de>, Chuck Ebbert <cebbert@redhat.com>,
Roland McGrath <roland@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Jeremy Fitzhardinge <jeremy@goop.org>,
zach@vmware.com
Subject: Re: [PATCH x86/mm 6/6] x86-64 ia32 ptrace get/putreg32 current task
Date: Thu, 29 Nov 2007 20:44:16 +0100 [thread overview]
Message-ID: <20071129194416.GB15245@elte.hu> (raw)
In-Reply-To: <20071129192721.GP24223@one.firstfloor.org>
* Andi Kleen <andi@firstfloor.org> wrote:
> For i386 iirc Jeremy/Zach did the benchmarking and they settled on %fs
> because it was faster for something (originally it was %gs too)
yep. IIRC, some CPUs only optimize %fs because that's what Windows uses
and leaves Linux with %gs out in the cold. There's also a performance
penalty for overlapping segment use, if the segment cache is single
entry only with an additional optimization for NULL [which just hides
the segment cache].
But if it's good for unification we could switch that to %gs again on
32-bit. I was one of the people who advocated the use of the 'other'
segment register, so that the hardware has less overlap, but clean and
unified code trumps this concern. It shouldnt be an issue on reasonably
modern CPUs anyway.
Ingo
next prev parent reply other threads:[~2007-11-29 19:44 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-29 0:38 [PATCH x86/mm 1/6] x86-64 ia32 ptrace pt_regs cleanup Roland McGrath
2007-11-29 0:40 ` [PATCH x86/mm 2/6] x86-64 ptrace whitespace Roland McGrath
2007-11-29 0:40 ` [PATCH x86/mm 3/6] x86-32 " Roland McGrath
2007-11-29 0:41 ` [PATCH x86/mm 4/6] x86-64 ptrace get/putreg current task Roland McGrath
2007-11-29 17:39 ` Christoph Hellwig
2007-11-29 0:42 ` [PATCH x86/mm 5/6] x86-32 " Roland McGrath
2007-11-29 0:42 ` [PATCH x86/mm 6/6] x86-64 ia32 ptrace get/putreg32 " Roland McGrath
2007-11-29 17:34 ` Chuck Ebbert
2007-11-29 18:09 ` Linus Torvalds
2007-11-29 18:16 ` H. Peter Anvin
2007-11-29 18:31 ` Linus Torvalds
2007-11-29 18:45 ` H. Peter Anvin
2007-11-29 19:08 ` Linus Torvalds
2007-11-29 19:16 ` H. Peter Anvin
2007-11-29 19:27 ` Andi Kleen
2007-11-29 19:44 ` Ingo Molnar [this message]
2007-11-29 20:01 ` H. Peter Anvin
2007-12-01 23:44 ` Jeremy Fitzhardinge
2007-11-29 19:49 ` Linus Torvalds
2007-11-29 20:11 ` Andi Kleen
2007-11-29 20:23 ` Linus Torvalds
2007-11-29 18:17 ` Chuck Ebbert
2007-11-29 18:23 ` H. Peter Anvin
2007-11-29 22:25 ` Roland McGrath
2007-11-29 22:34 ` Linus Torvalds
2007-11-29 22:21 ` Roland McGrath
2007-11-29 23:00 ` Chuck Ebbert
2007-11-29 10:39 ` [PATCH x86/mm 1/6] x86-64 ia32 ptrace pt_regs cleanup Ingo Molnar
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