[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] comment request: dom0 dma on large memory systems
----Original Message----- >From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx >[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Scott Parish >Sent: Friday, June 03, 2005 3:35 PM > >On x86_64 with 6gig ram, dom0's initial allocation is from memory >above the pci hole (referred to as "high memory" in this email) if >dom0_mem is set to 2g or higher. The only problem is that most io/dma >devices (non-dac) can only dma to the first 32bits worth of machine >addresses--thus for some configurations, dom0 has no memory which is >dma-able. IIRC, 2 or 3 months ago, Keir said that default memory allocation for Dom0 is all available memory. And then CP has to decrease by balloon interface before creating other domains. If this still holds true, I'm not sure whether above problem still exists, since all avail memory including both <4G and >4G belonging to Dom0 then. (XEN itself only consumes a small trunk). However after looking at your patch and then the source, it seems that only the max available order, meaning must be continuous, is allocated to Dom0 currently. So did I misunderstand this concept? If it really only means maximum continuous trunk, then you patch definitely shoots straight on the real problem on all 64bit platform. ;-) Thanks, Kevin _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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