Netflix posted a good article about how to analyze Linux performance issues using the following commands:
If you experience this error during boot: Kernel panic – not syncing: VFS: Unable to mount root fs on unknown-block(0,0) Pid: 1, comm: swapper Not tainted 2.6.32-431.el6.x86_64 Call Trace: [ <ffffffff81527823> ] ? panic+0xa7/0x16f [ <ffffffff81c27432> ] ? mount_block_root+0x2160x2cb [ <ffffffff81002930> ] ? bstat+0x2b0/0x980 [ <ffffffff81c2753d> ] ? mount_root+0x56/0x5a [ <ffffffff81c276b1> ] ? prepare_namespace+0x170/0x1a9 [ <ffffffff81c2692a> ] ? kernel_init+0x2e1/0x2f7… Read more »