From: "H. Peter Anvin" <hpa@zytor.com>
To: Christoph Lameter <cl@linux-foundation.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
Ingo Molnar <mingo@elte.hu>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Mike Travis <travis@sgi.com>,
Andrew Morton <akpm@linux-foundation.org>,
Jack Steiner <steiner@sgi.com>,
linux-kernel@vger.kernel.org,
Arjan van de Ven <arjan@infradead.org>
Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses
Date: Wed, 09 Jul 2008 16:35:45 -0400 [thread overview]
Message-ID: <48752121.3050208@zytor.com> (raw)
In-Reply-To: <48751CF9.4020901@linux-foundation.org>
Christoph Lameter wrote:
>
> Another reason to use a zero based per cpu area is to limit the offset range. Limiting the offset range allows in turn to limit the size of the generated instructions because it is part of the instruction. It also is easier to handle since __per_cpu_start does not figure
> in the calculation of the offsets.
>
No, that makes no difference. There is no short-offset form that
doesn't involve a register (ignoring the 16-bit 67h form on 32 bits.)
For 64 bits, you want to keep the offsets within %rip±2 GB, or you will
have relocation overflows for %rip-based forms; for absolute forms you
have to be in the range 0-4 GB. The %rip-based forms are shorter, and
I'm pretty sure they're the ones we currently generate. Since we base
the kernel at 0xffffffff80000000 (-2 GB) this means a zero-based offset
is actively wrong, and only work by accident (since the first
CONFIG_PHYSICAL_START of that space is unused.)
-hpa
next prev parent reply other threads:[~2008-07-09 20:43 UTC|newest]
Thread overview: 190+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-09 16:51 [RFC 00/15] x86_64: Optimize percpu accesses Mike Travis
2008-07-09 16:51 ` [RFC 01/15] x86_64: Cleanup early setup_percpu references Mike Travis
2008-07-09 16:51 ` [RFC 02/15] x86_64: Fold pda into per cpu area Mike Travis
2008-07-09 22:02 ` Eric W. Biederman
2008-07-13 17:54 ` Ingo Molnar
2008-07-14 14:24 ` Mike Travis
2008-07-09 16:51 ` [RFC 03/15] x86_64: Reference zero-based percpu variables offset from gs Mike Travis
2008-07-09 16:51 ` [RFC 04/15] x86_64: Replace cpu_pda ops with percpu ops Mike Travis
2008-07-09 16:51 ` [RFC 05/15] x86_64: Replace xxx_pda() operations with x86_xxx_percpu() Mike Travis
2008-07-09 16:51 ` [RFC 06/15] x86_64: Replace xxx_pda() operations in include_asm-x86_current_h Mike Travis
2008-07-09 16:51 ` [RFC 07/15] x86_64: Replace xxx_pda() operations in include_asm-x86_hardirq_64_h Mike Travis
2008-07-09 16:51 ` [RFC 08/15] x86_64: Replace xxx_pda() operations in include_asm-x86_mmu_context_64_h Mike Travis
2008-07-09 16:51 ` [RFC 09/15] x86_64: Replace xxx_pda() operations in include_asm-x86_percpu_h Mike Travis
2008-07-09 16:51 ` [RFC 10/15] x86_64: Replace xxx_pda() operations in include_asm-x86_smp_h Mike Travis
2008-07-09 16:51 ` [RFC 11/15] x86_64: Replace xxx_pda() operations in include_asm-x86_stackprotector_h Mike Travis
2008-07-09 16:51 ` [RFC 12/15] x86_64: Replace xxx_pda() operations in include_asm-x86_thread_info_h Mike Travis
2008-07-09 16:51 ` [RFC 13/15] x86_64: Replace xxx_pda() operations in include_asm-x86_topology_h Mike Travis
2008-07-09 16:51 ` [RFC 14/15] x86_64: Remove xxx_pda() operations Mike Travis
2008-07-09 16:51 ` [RFC 15/15] x86_64: Remove cpu_pda() macro Mike Travis
2008-07-09 17:19 ` [RFC 00/15] x86_64: Optimize percpu accesses H. Peter Anvin
2008-07-09 17:40 ` Mike Travis
2008-07-09 17:42 ` H. Peter Anvin
2008-07-09 18:05 ` Mike Travis
2008-07-09 17:44 ` Jeremy Fitzhardinge
2008-07-09 18:09 ` Mike Travis
2008-07-09 18:30 ` H. Peter Anvin
2008-07-09 19:34 ` Ingo Molnar
2008-07-09 19:44 ` H. Peter Anvin
2008-07-09 20:26 ` Adrian Bunk
2008-07-09 21:03 ` Mike Travis
2008-07-09 21:23 ` Jeremy Fitzhardinge
2008-07-25 15:49 ` Mike Travis
2008-07-25 16:08 ` Jeremy Fitzhardinge
2008-07-25 16:46 ` Mike Travis
2008-07-25 16:58 ` Jeremy Fitzhardinge
2008-07-25 18:12 ` Mike Travis
2008-07-09 17:27 ` Jeremy Fitzhardinge
2008-07-09 17:39 ` Christoph Lameter
2008-07-09 17:51 ` Jeremy Fitzhardinge
2008-07-09 18:14 ` Mike Travis
2008-07-09 18:22 ` Jeremy Fitzhardinge
2008-07-09 18:31 ` Mike Travis
2008-07-09 19:08 ` Jeremy Fitzhardinge
2008-07-09 18:02 ` Mike Travis
2008-07-09 18:13 ` Christoph Lameter
2008-07-09 18:26 ` Jeremy Fitzhardinge
2008-07-09 18:34 ` Christoph Lameter
2008-07-09 18:37 ` H. Peter Anvin
2008-07-09 18:48 ` Jeremy Fitzhardinge
2008-07-09 18:53 ` Christoph Lameter
2008-07-09 19:07 ` Jeremy Fitzhardinge
2008-07-09 19:12 ` Christoph Lameter
2008-07-09 19:32 ` Jeremy Fitzhardinge
2008-07-09 19:41 ` Ingo Molnar
2008-07-09 19:45 ` H. Peter Anvin
2008-07-09 19:52 ` Christoph Lameter
2008-07-09 20:00 ` Ingo Molnar
2008-07-09 20:09 ` Jeremy Fitzhardinge
2008-07-09 21:05 ` Mike Travis
2008-07-09 19:44 ` Christoph Lameter
2008-07-09 19:48 ` Jeremy Fitzhardinge
2008-07-09 18:27 ` Mike Travis
2008-07-09 18:46 ` Jeremy Fitzhardinge
2008-07-09 20:22 ` Eric W. Biederman
2008-07-09 20:35 ` Jeremy Fitzhardinge
2008-07-09 20:53 ` Eric W. Biederman
2008-07-09 21:03 ` Ingo Molnar
2008-07-09 21:16 ` H. Peter Anvin
2008-07-09 21:10 ` Arjan van de Ven
2008-07-09 23:20 ` Eric W. Biederman
2008-07-09 18:31 ` H. Peter Anvin
2008-07-09 18:00 ` Mike Travis
2008-07-09 19:05 ` Jeremy Fitzhardinge
2008-07-09 19:28 ` Ingo Molnar
2008-07-09 20:55 ` Mike Travis
2008-07-09 21:12 ` Ingo Molnar
2008-07-09 20:00 ` Eric W. Biederman
2008-07-09 20:05 ` Jeremy Fitzhardinge
2008-07-09 20:15 ` Ingo Molnar
2008-07-09 20:07 ` Ingo Molnar
2008-07-09 20:11 ` Jeremy Fitzhardinge
2008-07-09 20:18 ` Christoph Lameter
2008-07-09 20:33 ` Jeremy Fitzhardinge
2008-07-09 20:42 ` H. Peter Anvin
2008-07-09 20:48 ` Jeremy Fitzhardinge
2008-07-09 21:06 ` Eric W. Biederman
2008-07-09 21:16 ` H. Peter Anvin
2008-07-09 21:20 ` Jeremy Fitzhardinge
2008-07-09 21:25 ` Christoph Lameter
2008-07-09 21:36 ` H. Peter Anvin
2008-07-09 21:41 ` Jeremy Fitzhardinge
2008-07-09 22:22 ` Eric W. Biederman
2008-07-09 22:32 ` Jeremy Fitzhardinge
2008-07-09 23:36 ` Eric W. Biederman
2008-07-10 0:19 ` H. Peter Anvin
2008-07-10 0:24 ` Jeremy Fitzhardinge
2008-07-10 14:14 ` Christoph Lameter
2008-07-10 14:26 ` H. Peter Anvin
2008-07-10 15:26 ` Christoph Lameter
2008-07-10 15:42 ` H. Peter Anvin
2008-07-10 16:24 ` Christoph Lameter
2008-07-10 16:33 ` H. Peter Anvin
2008-07-10 16:45 ` Christoph Lameter
2008-07-10 17:33 ` Jeremy Fitzhardinge
2008-07-10 17:42 ` Christoph Lameter
2008-07-10 17:53 ` Jeremy Fitzhardinge
2008-07-10 17:55 ` H. Peter Anvin
2008-07-10 20:52 ` Christoph Lameter
2008-07-10 20:58 ` Jeremy Fitzhardinge
2008-07-10 21:03 ` H. Peter Anvin
2008-07-11 0:55 ` Mike Travis
2008-07-10 21:05 ` Christoph Lameter
2008-07-10 21:22 ` Eric W. Biederman
2008-07-10 21:29 ` H. Peter Anvin
2008-07-11 0:12 ` Mike Travis
2008-07-11 0:14 ` H. Peter Anvin
2008-07-11 0:58 ` Mike Travis
2008-07-11 1:41 ` H. Peter Anvin
2008-07-11 15:37 ` Christoph Lameter
2008-07-11 0:42 ` Eric W. Biederman
2008-07-11 15:36 ` Christoph Lameter
2008-07-10 17:53 ` H. Peter Anvin
2008-07-10 17:26 ` Eric W. Biederman
2008-07-10 17:38 ` Christoph Lameter
2008-07-10 19:11 ` Mike Travis
2008-07-10 19:12 ` Eric W. Biederman
2008-07-10 17:46 ` Mike Travis
2008-07-10 17:51 ` H. Peter Anvin
2008-07-10 19:09 ` Eric W. Biederman
2008-07-10 19:18 ` Mike Travis
2008-07-10 19:32 ` H. Peter Anvin
2008-07-10 23:37 ` Mike Travis
2008-07-10 20:17 ` Eric W. Biederman
2008-07-10 20:24 ` Ingo Molnar
2008-07-10 21:33 ` Eric W. Biederman
2008-07-11 1:39 ` Mike Travis
2008-07-11 2:57 ` Eric W. Biederman
2008-07-10 0:23 ` Jeremy Fitzhardinge
2008-07-09 20:35 ` H. Peter Anvin [this message]
2008-07-09 20:39 ` Arjan van de Ven
2008-07-09 20:44 ` H. Peter Anvin
2008-07-09 20:50 ` Jeremy Fitzhardinge
2008-07-09 21:12 ` H. Peter Anvin
2008-07-09 21:26 ` Jeremy Fitzhardinge
2008-07-09 21:37 ` H. Peter Anvin
2008-07-09 22:10 ` Eric W. Biederman
2008-07-09 22:23 ` H. Peter Anvin
2008-07-09 23:54 ` Eric W. Biederman
2008-07-10 16:22 ` Mike Travis
2008-07-10 16:25 ` H. Peter Anvin
2008-07-10 16:35 ` Christoph Lameter
2008-07-10 16:39 ` H. Peter Anvin
2008-07-10 16:47 ` Christoph Lameter
2008-07-10 17:21 ` Jeremy Fitzhardinge
2008-07-10 17:31 ` Christoph Lameter
2008-07-10 17:48 ` Jeremy Fitzhardinge
2008-07-10 18:00 ` H. Peter Anvin
2008-07-10 17:20 ` Mike Travis
2008-07-10 17:07 ` Jeremy Fitzhardinge
2008-07-10 17:12 ` Christoph Lameter
2008-07-10 17:25 ` Jeremy Fitzhardinge
2008-07-10 17:34 ` Christoph Lameter
2008-07-10 17:41 ` Mike Travis
2008-07-10 18:01 ` H. Peter Anvin
2008-07-10 20:51 ` Christoph Lameter
2008-07-10 20:58 ` H. Peter Anvin
2008-07-10 21:07 ` Christoph Lameter
2008-07-10 21:11 ` H. Peter Anvin
2008-07-11 15:32 ` Christoph Lameter
2008-07-11 16:07 ` H. Peter Anvin
2008-07-11 16:57 ` Eric W. Biederman
2008-07-11 17:10 ` H. Peter Anvin
2008-07-10 21:26 ` Eric W. Biederman
2008-07-10 18:48 ` Eric W. Biederman
2008-07-10 18:54 ` Jeremy Fitzhardinge
2008-07-10 19:18 ` Eric W. Biederman
2008-07-10 19:56 ` Jeremy Fitzhardinge
2008-07-10 20:22 ` Eric W. Biederman
2008-07-10 20:54 ` Jeremy Fitzhardinge
2008-07-11 6:59 ` Rusty Russell
2008-07-10 20:25 ` Eric W. Biederman
2008-07-10 17:57 ` H. Peter Anvin
2008-07-10 18:08 ` H. Peter Anvin
2008-07-09 20:46 ` Jeremy Fitzhardinge
2008-07-09 20:14 ` Arjan van de Ven
2008-07-09 20:33 ` Eric W. Biederman
2008-07-09 21:01 ` Ingo Molnar
2008-07-09 21:39 ` Mike Travis
2008-07-09 21:47 ` Jeremy Fitzhardinge
2008-07-09 21:55 ` Eric W. Biederman
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