From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Andi Kleen <ak@suse.de>,
Linux Memory Management <linux-mm@kvack.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2.6.13] lockless pagecache 2/7
Date: Sat, 03 Sep 2005 00:57:51 +0100 [thread overview]
Message-ID: <1125705471.30867.40.camel@localhost.localdomain> (raw)
In-Reply-To: <4318C28A.5010000@yahoo.com.au>
On Sad, 2005-09-03 at 07:22 +1000, Nick Piggin wrote:
> > Actually we have cmpxchg on i386 these days - we don't support
> > any SMP i386s so it's just done non atomically.
>
> Yes, I guess that's what Alan must have meant.
Well I was thinking about things like pre-empt. Also the x86 cmpxchg()
is defined for non i386 processors to allow certain things to use it
(ACPI, DRM etc) which know they won't be on a 386. The implementation in
this case will blow up on a 386 and the __HAVE_ARCH_CMPXCHG remains
false.
> but I suspect that SMP isn't supported on those CPUs without ll/sc,
> and thus an atomic_cmpxchg could be emulated by disabling interrupts.
It's obviously emulatable on any platform - the question is at what
cost. For x86 it probably isn't a big problem as there are very very few
people who need to build for 386 any more and there is already a big
penalty for such chips.
WARNING: multiple messages have this Message-ID (diff)
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Andi Kleen <ak@suse.de>,
Linux Memory Management <linux-mm@kvack.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2.6.13] lockless pagecache 2/7
Date: Sat, 03 Sep 2005 00:57:51 +0100 [thread overview]
Message-ID: <1125705471.30867.40.camel@localhost.localdomain> (raw)
In-Reply-To: <4318C28A.5010000@yahoo.com.au>
On Sad, 2005-09-03 at 07:22 +1000, Nick Piggin wrote:
> > Actually we have cmpxchg on i386 these days - we don't support
> > any SMP i386s so it's just done non atomically.
>
> Yes, I guess that's what Alan must have meant.
Well I was thinking about things like pre-empt. Also the x86 cmpxchg()
is defined for non i386 processors to allow certain things to use it
(ACPI, DRM etc) which know they won't be on a 386. The implementation in
this case will blow up on a 386 and the __HAVE_ARCH_CMPXCHG remains
false.
> but I suspect that SMP isn't supported on those CPUs without ll/sc,
> and thus an atomic_cmpxchg could be emulated by disabling interrupts.
It's obviously emulatable on any platform - the question is at what
cost. For x86 it probably isn't a big problem as there are very very few
people who need to build for 386 any more and there is already a big
penalty for such chips.
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next prev parent reply other threads:[~2005-09-02 23:33 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-02 6:25 New lockless pagecache Nick Piggin
2005-09-02 6:25 ` Nick Piggin
2005-09-02 6:28 ` [PATCH 2.6.13] lockless pagecache 1/7 Nick Piggin
2005-09-02 6:29 ` [PATCH 2.6.13] lockless pagecache 2/7 Nick Piggin
2005-09-02 6:30 ` [PATCH 2.6.13] lockless pagecache 3/7 Nick Piggin
2005-09-02 6:30 ` [PATCH 2.6.13] lockless pagecache 4/7 Nick Piggin
2005-09-02 6:31 ` [PATCH 2.6.13] lockless pagecache 5/7 Nick Piggin
2005-09-02 6:32 ` [PATCH 2.6.13] lockless pagecache 6/7 Nick Piggin
2005-09-02 6:32 ` [PATCH 2.6.13] lockless pagecache 7/7 Nick Piggin
2005-09-09 13:00 ` Christoph Lameter
2005-09-09 13:00 ` Christoph Lameter
2005-09-09 15:23 ` Nick Piggin
2005-09-09 15:23 ` Nick Piggin
2005-09-09 5:36 ` [PATCH 2.6.13] lockless pagecache 5/7 Christoph Lameter
2005-09-09 5:36 ` Christoph Lameter
2005-09-09 6:22 ` Nick Piggin
2005-09-09 6:22 ` Nick Piggin
2005-09-02 13:08 ` [PATCH 2.6.13] lockless pagecache 2/7 Alan Cox
2005-09-02 13:08 ` Alan Cox
2005-09-02 20:41 ` Andi Kleen
2005-09-02 20:41 ` Andi Kleen
2005-09-02 21:12 ` David S. Miller
2005-09-02 21:12 ` David S. Miller, Andi Kleen
2005-09-02 21:43 ` Nick Piggin
2005-09-02 21:43 ` Nick Piggin
2005-09-02 21:22 ` Nick Piggin
2005-09-02 21:22 ` Nick Piggin
2005-09-02 21:31 ` David S. Miller
2005-09-02 21:31 ` David S. Miller, Nick Piggin
2005-09-02 21:47 ` Nick Piggin
2005-09-02 21:47 ` Nick Piggin
2005-09-02 21:57 ` David S. Miller
2005-09-02 21:57 ` David S. Miller, Nick Piggin
2005-09-02 23:57 ` Alan Cox [this message]
2005-09-02 23:57 ` Alan Cox
2005-09-03 1:40 ` Nick Piggin
2005-09-03 1:40 ` Nick Piggin
2005-09-03 17:31 ` Alan Cox
2005-09-03 17:31 ` Alan Cox
2005-09-04 1:01 ` Nick Piggin
2005-09-04 1:01 ` Nick Piggin
2005-09-04 8:20 ` Alan Cox
2005-09-04 8:20 ` Alan Cox
2005-09-06 1:03 ` Nick Piggin
2005-09-06 1:03 ` Nick Piggin
2005-09-02 18:26 ` Christoph Lameter
2005-09-02 18:26 ` Christoph Lameter
2005-09-02 21:26 ` Nick Piggin
2005-09-02 21:26 ` Nick Piggin
2005-09-03 1:33 ` Christoph Lameter
2005-09-03 1:33 ` Christoph Lameter
2005-09-02 6:45 ` New lockless pagecache Nick Piggin
2005-09-02 6:45 ` Nick Piggin
2005-09-15 19:50 ` Alok kataria
2005-09-16 3:12 ` Nick Piggin
2005-09-16 3:12 ` Nick Piggin
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