From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steffen Persvold Date: Thu, 17 Oct 2002 18:16:48 +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 Mon, 14 Oct 2002, Bjorn Helgaas wrote: > On Monday 14 October 2002 12:17 pm, Steffen Persvold wrote: > > 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. > > I'm really not opposed to having it in the kernel headers. The thing > is, we were allowing WC mappings regardless of whether the hardware > actually supported them. What we need is some mechanism for > looking at the EFI memory map, which tells us what attributes are > supported. Which IA64 hardware doesn't support _PAGE_MA_WC in the PTE ? My IA64 docs doesn't mention anything about that. > > We've got a mechanism for looking up the supported attributes > (efi_mem_attributes()); what I'd really like is for somebody to > hook that up with the mmap infrastructure so that we only allow > the supported attributes. Actually I think _PAGE_MA_WC is only applicable to IO memory the same way as _PAGE_MA_UC is. Can't it be handled in the same way ? (you've already done the fix for UC, right ?) 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