From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] [PATCH 1/5] PCI DMA API (v3) Date: Sun, 20 Apr 2008 14:29:43 -0500 Message-ID: <480B99A7.5050207@us.ibm.com> References: <1208297491-1287-1-git-send-email-aliguori@us.ibm.com> <4806596C.4090107@us.ibm.com> <4807ADA7.7000500@us.ibm.com> <480A4FDA.3070706@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net, Marcelo Tosatti , qemu-devel@nongnu.org, Aurelien Jarno , Paul Brook To: Blue Swirl Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org Blue Swirl wrote: > On 4/19/08, Anthony Liguori wrote: > > Well, the IOVector part and bdrv_readv look OK, except for the heavy > mallocing involved. > I don't think that in practice, malloc is going to have any sort of performance impact. If it does, it's easy enough to implement a small object allocator for common, small vector sizes. > I'm not so sure about the DMA side and how everything fits together > for zero-copy IO. For example, do we still need explicit translation > at some point? I'm thinking that zero copy will be implemented by setting the map and unmap functions to NULL by default (instead of to the PCI read/write functions). Then the bus can decide whether copy functions are needed. I'll send an updated patch series tomorrow that includes this functionality. Regards, Anthony Liguori ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone