Hi, In start_info, there is a field nr_pages definig how much memory is allocated to the domain, which is obvious. While in shared_info, there is a field max_pfn. I don''t know why max_pfn is not equal to nr_pages. Say for 32MB memory, nr_pages = 8192, while max_pfn = 10240 (may vary?), of which 2048 pfn''s have invalid mfn. Can anybody explain that why max_pfn is larger? Is it static or dynamic? Furture, does pfn to mfn frame mapping ever change? Hopefully not. Thanks, Shawn _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
The shared_info value is set up by the guest itself during boot. It''s larger because Linux adds extra space at the end of its p2m map for backend drivers. -- Keir On 19/11/08 09:45, "Y. D." <duyuyang@gmail.com> wrote:> Hi, > > In start_info, there is a field nr_pages definig how much memory is allocated > to the domain, which is obvious. > While in shared_info, there is a field max_pfn. I don''t know why max_pfn is > not equal to nr_pages. > Say for 32MB memory, nr_pages = 8192, while max_pfn = 10240 (may vary?), of > which 2048 pfn''s have invalid mfn. > Can anybody explain that why max_pfn is larger? Is it static or dynamic? > Furture, does pfn to mfn frame mapping ever change? Hopefully not. > > Thanks, > Shawn > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir, does Dom0 Linux do this for each Mini-OS instance that is spawned? If so then shouldn''t the memory usage value in xm list for each PV guest take into account this additional usage of memory? i.e. 32MB + 8MB? Bhaskar. -----Original Message----- From: xen-devel-bounces@lists.xensource.com [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Keir Fraser Sent: Wednesday, November 19, 2008 3:24 PM To: Y. D.; xen-devel Subject: Re: [Xen-devel] Different: nr_pages vs. max_pfn The shared_info value is set up by the guest itself during boot. It''s larger because Linux adds extra space at the end of its p2m map for backend drivers. -- Keir On 19/11/08 09:45, "Y. D." <duyuyang@gmail.com> wrote:> Hi, > > In start_info, there is a field nr_pages definig how much memory is allocated > to the domain, which is obvious. > While in shared_info, there is a field max_pfn. I don''t know why max_pfn is > not equal to nr_pages. > Say for 32MB memory, nr_pages = 8192, while max_pfn = 10240 (may vary?), of > which 2048 pfn''s have invalid mfn. > Can anybody explain that why max_pfn is larger? Is it static or dynamic? > Furture, does pfn to mfn frame mapping ever change? Hopefully not. > > Thanks, > Shawn > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
>The shared_info value is set up by the guest itself during boot. It''s larger >because Linux adds extra space at the end of its p2m map for backend >drivers.I tested for various memories, i.e. 64M and 128M, the extra memory is 8M unchanged. Also, I tested the extra 8M memory is dispersed in the p2m map, not at the end totally. Can we say the p2m mapping table stays put during dom''s lifecycle? Thanks, keir. Shawn _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel