From: Andi Kleen <ak@suse.de>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Andi Kleen <ak@suse.de>,
Grant Grundler <grundler@parisc-linux.org>,
James Bottomley <James.Bottomley@SteelEye.com>,
axboe@suse.de, davem@redhat.com, suparna@in.ibm.com,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
alex_williamson@hp.com, bjorn_helgaas@hp.com
Subject: Re: [RFC] block layer support for DMA IOMMU bypass mode II
Date: Thu, 3 Jul 2003 23:24:15 +0200 [thread overview]
Message-ID: <20030703212415.GA30277@wotan.suse.de> (raw)
In-Reply-To: <1057263988.21508.18.camel@dhcp22.swansea.linux.org.uk>
On Thu, Jul 03, 2003 at 09:26:29PM +0100, Alan Cox wrote:
> On Iau, 2003-07-03 at 00:56, Andi Kleen wrote:
> > > 1. We allocate pages in reverse order so most merges cant occur
> >
> > I added an printk and I get quite a lot of merges during bootup
> > with normal IDE.
> >
> > (sometimes 12+ segments)
>
> Thats merging adjacent blocks with non adjacent page targets using the
> IOMMU right - I was doing mergign without an IOMMU which is a little
Yep.
> different and turns out to be a waste of cpu
Understandable. Especially when memory fragments after some uptime.
But of course it doesn't help much in practice because all the interesting
block devices support DAC anyways and the IOMMU is disabled for that.
Also it's likely cheaper just submit more segments than to have the IOMMU
overhead
(at least for sane devices, if not it may be worth to artificially limit the
dma mask of the device to force IOMMU on IA64 and x86-64)
-Andi
next prev parent reply other threads:[~2003-07-03 21:09 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-01 16:46 [RFC] block layer support for DMA IOMMU bypass mode James Bottomley
2003-07-01 17:09 ` Andi Kleen
2003-07-01 17:28 ` James Bottomley
2003-07-01 17:42 ` Andi Kleen
2003-07-01 19:22 ` Grant Grundler
2003-07-01 19:56 ` James Bottomley
2003-07-01 17:54 ` H. Peter Anvin
2003-07-01 19:19 ` Grant Grundler
2003-07-01 19:59 ` Alex Williamson
2003-07-01 20:11 ` James Bottomley
2003-07-01 20:03 ` James Bottomley
2003-07-01 23:01 ` Grant Grundler
2003-07-02 15:52 ` James Bottomley
2003-07-01 22:51 ` David S. Miller
2003-07-01 23:57 ` [RFC] block layer support for DMA IOMMU bypass mode II Andi Kleen
2003-07-02 0:03 ` David S. Miller
2003-07-02 0:22 ` Andi Kleen
2003-07-02 0:21 ` David S. Miller
2003-07-02 16:53 ` Grant Grundler
2003-07-02 17:19 ` Andi Kleen
2003-07-02 16:55 ` Grant Grundler
2003-07-02 17:20 ` Andi Kleen
2003-07-02 17:37 ` Grant Grundler
2003-07-02 21:16 ` Alan Cox
2003-07-02 23:56 ` Andi Kleen
2003-07-03 20:26 ` Alan Cox
2003-07-03 21:24 ` Andi Kleen [this message]
2003-07-03 22:19 ` Grant Grundler
2003-07-08 2:14 ` David S. Miller
2003-07-08 19:34 ` Andi Kleen
2003-07-08 19:47 ` Jeff Garzik
2003-07-08 20:10 ` Andi Kleen
2003-07-08 20:11 ` Grant Grundler
2003-07-08 22:04 ` David S. Miller
2003-07-08 22:25 ` Grant Grundler
2003-07-08 22:23 ` David S. Miller
2003-07-09 18:55 ` Andi Kleen
2003-07-23 11:40 ` Grant Grundler
2003-07-28 11:15 ` Andi Kleen
2003-07-28 14:59 ` Grant Grundler
2003-07-30 2:31 ` Grant Grundler
2003-08-01 21:51 ` Cliff White
2003-08-01 23:18 ` reaim now available as osdl-aim-7 - " Cliff White
2003-07-30 4:42 ` Grant Grundler
2003-07-30 4:51 ` David S. Miller
2003-07-30 13:06 ` Grant Grundler
2003-07-30 16:02 ` Grant Grundler
2003-07-30 16:36 ` Andi Kleen
2003-07-30 17:18 ` James Bottomley
2003-07-30 14:20 ` James Bottomley
2003-07-23 13:20 ` Grant Grundler
2003-07-23 15:30 ` Jens Axboe
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