From: "H. Peter Anvin" <hpa@zytor•com>
To: Christoph Lameter <cl@linux-foundation•org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl•ca>,
Rusty Russell <rusty@rustcorp•com.au>, Tejun Heo <tj@kernel•org>,
Ingo Molnar <mingo@elte•hu>,
Herbert Xu <herbert@gondor•apana.org.au>,
akpm@linux-foundation•org, brgerst@gmail•com,
ebiederm@xmission•com, travis@sgi•com,
linux-kernel@vger•kernel.org, steiner@sgi•com, hugh@veritas•com,
"David S. Miller" <davem@davemloft•net>,
netdev@vger•kernel.org
Subject: Re: [PATCH] percpu: add optimized generic percpu accessors
Date: Thu, 29 Jan 2009 10:48:43 -0800 [thread overview]
Message-ID: <4981FA0B.5010101@zytor.com> (raw)
In-Reply-To: <alpine.DEB.1.10.0901291315320.9622@qirst.com>
Christoph Lameter wrote:
>
> gcc/glibc support a __thread attribute to variables. As far as I can tell
> this automatically makes gcc perform the relocation to the current
> context using a segment register.
>
> But its a weird ABI http://people.redhat.com/drepper/tls.pdf. After
> reading that I agree that we should stay with the cpu ops and forget about
> the local and thread stuff in gcc/glibc.
>
We have discussed this a number of times. There are several issues with
it; one being that per-cpu != per-thread (we can switch CPU whereever
we're preempted), and another that many versions of gcc uses hardcoded
registers, in particular %fs on 64 bits, but the kernel *has* to use %gs
since there is no swapfs instruction.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2009-01-29 18:49 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20090115183942.GA6325@elte.hu>
[not found] ` <20090116001200.GA9137@gondor.apana.org.au>
[not found] ` <20090116001544.GA11073@elte.hu>
2009-01-16 0:18 ` [PATCH] percpu: add optimized generic percpu accessors Herbert Xu
[not found] ` <200901170827.33729.rusty@rustcorp.com.au>
2009-01-16 22:08 ` Ingo Molnar
[not found] ` <200901201328.24605.rusty@rustcorp.com.au>
2009-01-20 6:25 ` Tejun Heo
2009-01-20 10:36 ` Ingo Molnar
[not found] ` <200901271213.18605.rusty@rustcorp.com.au>
2009-01-27 2:24 ` Tejun Heo
2009-01-27 13:13 ` Ingo Molnar
2009-01-27 23:07 ` Tejun Heo
2009-01-28 3:36 ` Tejun Heo
2009-01-28 8:12 ` Tejun Heo
2009-01-27 20:08 ` Christoph Lameter
2009-01-27 21:47 ` David Miller
2009-01-27 22:47 ` Rick Jones
2009-01-28 0:17 ` Luck, Tony
2009-01-28 16:48 ` Christoph Lameter
2009-01-28 17:15 ` Luck, Tony
2009-01-28 16:45 ` Christoph Lameter
2009-01-28 20:47 ` David Miller
2009-01-28 10:38 ` Rusty Russell
2009-01-28 10:56 ` Tejun Heo
2009-01-29 2:06 ` Rusty Russell
2009-01-31 6:11 ` Tejun Heo
2009-01-28 16:50 ` Christoph Lameter
2009-01-28 18:07 ` Mathieu Desnoyers
2009-01-29 18:33 ` Christoph Lameter
2009-01-29 18:48 ` H. Peter Anvin [this message]
2009-01-20 10:40 ` Ingo Molnar
2009-01-21 5:52 ` Tejun Heo
2009-01-21 10:05 ` Ingo Molnar
2009-01-21 11:21 ` Eric W. Biederman
2009-01-21 12:45 ` Stephen Hemminger
2009-01-21 14:13 ` Eric W. Biederman
2009-01-21 20:34 ` David Miller
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