From: Andi Kleen <ak@suse.de>
To: Matthew Wilcox <willy@debian.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Memory mapped IO vs Port IO
Date: Thu, 11 Sep 2003 18:31:36 +0200 [thread overview]
Message-ID: <20030911183136.01dfeb53.ak@suse.de> (raw)
In-Reply-To: <20030911162504.GL21596@parcelfarce.linux.theplanet.co.uk>
On Thu, 11 Sep 2003 17:25:04 +0100
Matthew Wilcox <willy@debian.org> wrote:
> On Thu, Sep 11, 2003 at 06:17:02PM +0200, Andi Kleen wrote:
> > The overhead of checking for PIO vs mmio at runtime in the drivers
> > should be completely in the noise on any non ancient CPU (both MMIO
> > and PIO typically take hundreds or thousands of CPU cycles for the bus
> > access, having an dynamic function call or an if before that is makes
> > no difference at all)
>
> That's not true for MMIO writes which are posted. They should take
> no longer than a memory write. For MMIO reads and PIO reads & writes,
> you are, of course, correct.
Even a memory write is tens to hundres of cycles.
-Andi
next prev parent reply other threads:[~2003-09-11 16:31 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20030911160116.GI21596@parcelfarce.linux.theplanet.co.uk.suse.lists.linux.kernel>
2003-09-11 16:17 ` Memory mapped IO vs Port IO Andi Kleen
2003-09-11 16:25 ` Matthew Wilcox
2003-09-11 16:31 ` Andi Kleen [this message]
2003-09-11 16:42 ` Matthew Wilcox
2003-09-11 17:12 ` Jamie Lokier
2003-09-11 17:25 ` Andi Kleen
2003-09-12 1:39 ` jw schultz
2003-09-12 16:10 ` Anthony Dominic Truong
2003-09-12 16:22 ` Jamie Lokier
2003-09-12 16:27 ` Jesse Barnes
2003-09-12 17:48 ` Jesse Barnes
2003-09-11 17:13 ` Jamie Lokier
[not found] ` <20030911161450.GA23536@sgi.com.suse.lists.linux.kernel>
2003-09-11 16:20 ` Andi Kleen
[not found] <20030911192550.7dfaf08c.ak@suse.de.suse.lists.linux.kernel>
[not found] ` <1063308053.4430.37.camel@huykhoi.suse.lists.linux.kernel>
[not found] ` <20030912162713.GA4852@sgi.com.suse.lists.linux.kernel>
[not found] ` <20030912174807.GA629@sgi.com.suse.lists.linux.kernel>
2003-09-12 18:00 ` Andi Kleen
2003-09-12 18:04 ` Jesse Barnes
2003-09-12 18:09 ` Andi Kleen
2003-09-12 18:11 ` Tim Hockin
2003-09-12 18:24 ` Jesse Barnes
2003-09-12 18:29 ` Andi Kleen
2003-09-12 18:58 ` Martin J. Bligh
2003-09-12 19:51 ` Jesse Barnes
2003-09-12 16:41 John Bradford
2003-09-12 21:52 ` Mike Fedyk
2003-09-13 4:01 ` Mike Fedyk
-- strict thread matches above, loose matches on Subject: below --
2003-09-11 16:01 Matthew Wilcox
2003-09-11 16:14 ` Måns Rullgård
2003-09-11 16:14 ` Jesse Barnes
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