From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Nick Piggin <npiggin@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hugh@veritas.com>,
Linux Memory Management List <linux-mm@kvack.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [patch] i386: avoid expensive ppro ordering workaround for default 686 kernels
Date: Fri, 4 Jan 2008 16:27:00 +0000 [thread overview]
Message-ID: <20080104162700.3aef1806@lxorguk.ukuu.org.uk> (raw)
In-Reply-To: <20080103231017.GA25880@wotan.suse.de>
> > The cost on a 586 SMP box (ie pentium) is basically nil. All cross CPU
> > transactions are hideously slow anyway locked or not.
>
> That's wrong. Firstly, spinlocks are very often retaken by the same CPU, and they
Go time it. It certainly used to be the case.
> On 586 SMP systems, didn't lock ops actually go out on the bus, and hence are much
> more expensive than they are today (although today they are still one or two orders
> of magnitude more expensive than regular memory ops).
All cross CPU cache stuff goes that way, not that may P5 SMP boxes are
running today except in Mr Bottomley's residence.
> And if you build a kernel which is to support 686, PII, and later, you don't want
> them by default either, most probably.
I want a kernel for VIA C3 or later which happens to include K6 (still
common), PII+ and maybe not PPro.
So your patch should go in the bitbucket by the sound of it and Adrian's
get merged.
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next prev parent reply other threads:[~2008-01-04 16:27 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-18 1:26 [patch] mm: fix PageUptodate memory ordering bug Nick Piggin
2007-12-22 8:57 ` Andrew Morton
2007-12-22 12:14 ` Hugh Dickins
2007-12-23 6:54 ` Nick Piggin
2007-12-23 5:57 ` Nick Piggin
2007-12-23 6:32 ` Andrew Morton
2007-12-23 7:15 ` Nick Piggin
2007-12-23 7:29 ` Andrew Morton
2007-12-23 9:14 ` Nick Piggin
2007-12-23 9:28 ` Andrew Morton
2007-12-23 16:02 ` Andi Kleen
2007-12-30 16:33 ` Ingo Molnar
2008-01-01 23:26 ` Nick Piggin
2008-01-02 21:01 ` Andi Kleen
2008-01-03 3:32 ` Nick Piggin
2008-01-03 13:08 ` Andi Kleen
2007-12-23 17:22 ` Linus Torvalds
2007-12-23 21:35 ` Nick Piggin
2007-12-23 22:41 ` Nick Piggin
2008-01-01 23:41 ` Alan Cox
2008-01-02 11:02 ` [patch] i386: avoid expensive ppro ordering workaround for default 686 kernels Nick Piggin
2008-01-02 13:44 ` Alan Cox
2008-01-03 4:17 ` Nick Piggin
2008-01-03 14:23 ` Alan Cox
2008-01-03 20:20 ` Benjamin Herrenschmidt
2008-01-03 22:23 ` Alan Cox
2008-01-03 23:10 ` Nick Piggin
2008-01-04 16:27 ` Alan Cox [this message]
2008-01-07 0:12 ` Nick Piggin
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