CPAN, Perl modules, and yum

Many tools out there to learn:

perldoc -q 'How do I install a module from CPAN'

Do a 'yum update' after installing a "repository package" such as CPAN

Understanding Linux top output:

wa = wiating for IO
us = userspace
sy = system/kernel
ni = nice processs
id = idle
hi = hardware interrupts
si = software interrupts

Overlay network vs. Virtual machine

Both are another layer of abstraction above the native resource. Anyway we can leverage existing studies in VM to overlay network?

Installing TraceFS

1. Need to copy over fs.h and syscalls.h
2. System crashed when doing "mount -t tracefs"

Understainding ext2fs library

Useful tool:

1. debugfs -R show_super_stats
2. Kernel hlist doesn't really do hash. You still need to write your own hash functions

Part 1: inode.c

1. get_next_blockgroup() doesn't really do the I/O. It just "gets ready" for reading the next block group.

Different asynchronous I/O methods in Linux

1. Library (aio_read, aio_write). This requires no kernel support. It just forks out a child process doing I/O. This is the "poor man's" version of asynchronous I/O
2. Kernel support. This is available in 2.6 kernel. It uses functions like io_setup, io_submit, io_getevents, etc..

How to use shared libraries in Linux

Note that LD_LIBRARY_PATH is to be set before the program run. In other words, the variable is to be used AT RUN TIME.