I asked this question in many forums and IRC,but didnt get proper explanation. Can someone explain to me why there is a memory difference in Guests with the same configuration? - *Hypervisor*: xen 4.2 64 bit - *VM1*: Centos 5.7 with 2.6.18-274.el5xen Assigned memory from xen is exactly the same as memory inside guest, 524288k (512m): free -k total used free shared buffers cached Mem: 524288 445004 79284 0 18040 182652 -/+ buffers/cache: 244312 279976 Swap: 524280 0 524280 despite showing: " Memory: 500984k/524288k available (2533k kernel code, 23212k reserved, 1746k data, 196k init) " dmesg: http://pastebin.com/FmVRniLJ *Question1:* Why does free show exact memory, while dmesg clearly showed 2.5MB for kernel code and 23MB as reserved? - *VM2:* Ubuntu 12.04 ,3.2.0-48- For the same resources Ubuntu 12.04 with pvopskernel is showing 501236k. free -k total used free shared buffers cached Mem: 501236 147188 354048 0 12588 87668 -/+ buffers/cache: 46932 454304 Swap: 0 0 0 dmesg: http://pastebin.com/jgNfcxc5 Memory: 481820k/524288k available (6553k kernel code, 448k absent, 42020k reserved, 6642k data, 924k init) *Question2:* What might be the reason for this behavior, can this have something to do with with pvops kernel, or is it because of changes in Linux 3.0+ Memory Management? Regards, Ananthan _______________________________________________ Xen-users mailing list Xen-users@lists.xen.org http://lists.xen.org/xen-users