Hi guys, Im fairly new to the Xen Development & trying to understand ballooning. While compiling a DomU kernel I''m trying to understand the e820 memory map w.r.t Xen, I have modified arch/x86/xen/setup.c EXTRA_MEM_RATIO to 1 and can see that the guest can not balloon up more than 2GB. Below is the memory map of DomU with max mem as 16GB. for EXTRA_MEM_RATIO = 1 BIOS-provided physical RAM map: Xen: 0000000000000000 - 00000000000a0000 (usable) Xen: 00000000000a0000 - 0000000000100000 (reserved) Xen: 0000000000100000 - 0000000080000000 (usable) Xen: 0000000080000000 - 0000000400000000 (unusable) NX (Execute Disable) protection: active DMI not present or invalid. e820 update range: 0000000000000000 - 0000000000010000 (usable) ==> (reserved) e820 remove range: 00000000000a0000 - 0000000000100000 (usable) No AGP bridge found last_pfn = 0x80000 max_arch_pfn = 0x400000000 initial memory mapped : 0 - 0436c000 Base memory trampoline at [ffff88000009b000] 9b000 size 20480 init_memory_mapping: 0000000000000000-0000000080000000 0000000000 - 0080000000 page 4k kernel direct mapping tables up to 80000000 @ bfd000-1000000 xen: setting RW the range fd6000 - 1000000 for EXTRA_MEM_RATIO = 10 the map is like below and can balloon up to 16GB. BIOS-provided physical RAM map: Xen: 0000000000000000 - 00000000000a0000 (usable) Xen: 00000000000a0000 - 0000000000100000 (reserved) Xen: 0000000000100000 - 0000000400000000 (usable) NX (Execute Disable) protection: active DMI not present or invalid. e820 update range: 0000000000000000 - 0000000000010000 (usable) ==> (reserved) e820 remove range: 00000000000a0000 - 0000000000100000 (usable) No AGP bridge found last_pfn = 0x400000 max_arch_pfn = 0x400000000 last_pfn = 0x100000 max_arch_pfn = 0x400000000 initial memory mapped : 0 - 0436c000 Base memory trampoline at [ffff88000009b000] 9b000 size 20480 init_memory_mapping: 0000000000000000-0000000100000000 0000000000 - 0100000000 page 4k kernel direct mapping tables up to 100000000 @ 7fb000-1000000 xen: setting RW the range fd6000 - 1000000 init_memory_mapping: 0000000100000000-0000000400000000 0100000000 - 0400000000 page 4k kernel direct mapping tables up to 400000000 @ 601ef000-62200000 xen: setting RW the range 619fb000 - 62200000 Can someone please help me understand its behavior and importance ? Thanks. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
On Sun, 2013-06-02 at 03:29 +0530, Rushikesh Jadhav wrote:> for EXTRA_MEM_RATIO = 10 the map is like below and can balloon up to > 16GB. > [...]> Can someone please help me understand its behavior and importance ?There are large comments before both the definition and use of the EXTRA_MEM_RATIO value. I think these make it pretty clear what it does and what it is for, which aspect is not clear to you? You might also find it useful to use git annotate or git log on the file to track down the original commit and see if the commit message provides any enlightenment. Ian.