What’s virtual address limit of 32bit/64bit Linux kernel?

RHEL 5 code 32bit: include/asm-i386/processor.h /* * User space process size: 3GB (default). */ #define TASK_SIZE (PAGE_OFFSET) 64bit: include/asm-x86_64/processor.h /* * User space process size. 47bits minus one guard page. */ #define TASK_SIZE64 (0x800000000000UL - 4096) /* This decides where the kernel will search for a free chunk of vm * space during mmap's. */… Continue reading What’s virtual address limit of 32bit/64bit Linux kernel?

Personal memo for ‘Automatic NUMA Balancing’

Automatic NUMA Balancing It is described in Documentation/sysctl/kernel.txt numa_balancing Enables/disables automatic page fault based NUMA memory balancing. Memory is moved automatically to nodes that access it often. Enables/disables automatic NUMA memory balancing. On NUMA machines, there is a performance penalty if remote memory is accessed by a CPU. When this feature is enabled the kernel… Continue reading Personal memo for ‘Automatic NUMA Balancing’

Build a OpenStack on VMware Fusion 5

Cloud is a big trend in recent years and it will be bigger and bigger. Even though you want to join in this trend, it's hard as it requires lots of machines to build and test it. Fortunately, these days virtualisation technique allows us to install virtual guest on top of another virtual quest. So,… Continue reading Build a OpenStack on VMware Fusion 5

Very very very very very simple boot up code.

I think it's 2003 or 2004 that I made this very simple booting code to demonstrate how OS starts. I paste the output here for the future reference. bootsec.asm ORG 0x7c00 jmp begin_boot bootmesg1 db "Press any to boot KERNEL....." mesglen equ $ - bootmesg1 drive db 0 [BITS 16] print_mesg: mov ah, 0x13 mov… Continue reading Very very very very very simple boot up code.

Stack Exchange Client for iPhone

As a developer/engineer, I spent quite some time on stackoverflow.com. When I try to search something on google, it also forwarded me to stackoverflow.com. This site has really great resources with very clear interface. There are also some other topics that cover with stackexchange API such as Gaming, Photography, and Cooking. So, I decided to… Continue reading Stack Exchange Client for iPhone