On Fri, 26 Mar 2010 13:45:44 -0700 Philip Guenther <[email protected]> wrote:
> > As for dmesg picking the right kernel file for getting the names of > > the currently running kernel, there is either some magic in demsg > > which picks the right kernel from disk, or a properly running > > kernel does not need to read names from the kernel file since > > they're already in memory. > > It's simpler than that: when run without the -N or -M options, dmesg > gets the info via sysctl() instead of trying to read from /dev/kmem. > This makes it ABI-proof against various kernel or libkvm changes that > break code that reads /dev/kmem. > > That's true not just of dmesg but of all the other programs that need > kernel info: ps, netstat, fstat, ipcs, systat, etc. > > $ sysctl -A kern 2>&1 >/dev/null | grep 'use ' | head > sysctl: use pstat to view kern.vnode information > sysctl: use ps to view kern.proc information > sysctl: use pstat to view kern.file information > sysctl: use pstat -t to view kern.tty.ttyinfo information > sysctl: use dmesg to view kern.msgbuf > sysctl: use netstat to view kern.mbstat > sysctl: use ps to view kern.proc2 information > sysctl: use fstat to view kern.file2 information > sysctl: use vmstat or systat to view vm.vmmeter information > sysctl: use vmstat or systat to view vm.uvmexp information > $ > > Make sense? Yep. Thank you. I knew at least some of the data was available through sysctl, but I didn't know how, or more importantly, why. The ABI-proffing makes sense. jcr
