From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steffen Persvold Date: Mon, 14 Oct 2002 18:17:43 +0000 Subject: Re: [Linux-ia64] BitKeeper tree for 2.4.x Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Thu, 10 Oct 2002, Bjorn Helgaas wrote: > NOTE: I removed the mmap support for MAP_WRITECOMBINED and > MAP_NONCACHED to avoid issues with memory attribute aliasing. > The only user of these that I know about is XFree86, which still > seems functional when we ignore the attributes it requests. I'm > very interested in any problems caused by this change. > Well, without MAP_WRITECOMBINED, streaming PIO accesses to the PCI bus drops from 330MByte/sec to approx. 100MByte/s using the Dolphin SCI card. This is an rather significant drop which makes the IA64 platform kind of uninteresting for high performance clustering (the Dolphin SCI cards are used for shared memory message passing between nodes). We can of course hack this in for our usage (in our kernel driver) if you are totally against having it in the kernel headers, but I think since the hardware allows different mapping types, the kernel should take advantage of it. Regards, -- Steffen Persvold | Scali AS mailto:sp@scali.com | http://www.scali.com Tel: (+47) 2262 8950 | Olaf Helsets vei 6 Fax: (+47) 2262 8951 | N0621 Oslo, NORWAY