Hi, I''m seeing an issue with 4.0.1 on Debian 6 regarding "missing" memory. My set up: * Xen 4.0.1 on Debian 6.0.5 * dom0-min-mem 512, enable-dom0-ballooning no, dom0_mem=512M (GRUB config). (I also tried with dom0-min-mem 0) * Host server has 32GB RAM # xm list Name ID Mem VCPUs State Time(s) Domain-0 0 501 8 r----- 12.0 # xm info|grep memory total_memory : 32758 free_memory : 31832 32758 (total) - 31832 (''free_memory'') - 512 (dom0) = 414MB unaccounted. (No domus are running) I created an HVM domU with 31488 MB RAM (N.B. this is less than 31832 reported by xm info free_memory plus I calculated about ~250MB memory overhead) and 4 VCPUs but it wouldn''t start due to insufficient memory available. I expected it to fit. Is there an official calculation for the memory overhead (for tables/caches etc)? Can anyone explain why a domu with 31,488MB won''t start when 31,832MB is free? I''m trying to calculate the most amount of RAM a domU can have (i.e. to occupy an entire server) Thanks. -- Andrew Wade Memset Ltd., registration number 4504980. 25 Frederick Sanger Road, Guildford, Surrey, GU2 7YD, UK.