Tool to see what processes are doing IO. Akin to iotop, but with fewer dependencies.
So, you're a sysadmin: and you know (from iostat, and whatnot) that you've got a drive that's getting hammered. Wouldn't it be nice to know what process is actually hammering it? There are things out there like iotop[1] and what not, but they generally rely on new kernel features, or things that are rather more invasive. Over the weekend, I needed something for an older kernel, and which wouldn't be invasive.
Enter iohist (with a nice tip o' the hat to iodump[2]). It relies on 'echo 1 > /proc/sys/vm/block_dump' to do it's magic, looping over 'dmesg -c' at an interval (currently 5 seconds).
NOTE: this program does the 'echo 1 > /proc/sys/vm/block_dump' for you... technically it sees if it's a zero value, overrides it if it is, and reverts it back when you exit.
Goals:
- a few more configuration options (like allowing a change of the interval from 5 seconds)
- Maybe get more clever about translating dm-6 into 'this is your swap partition'
Useful additions: I think it's beyond the scope of this tool to translate sda4 to 'swap' or dm-6 to '/var', or 'VxVM3822' to '/u01'. There's too much in there to swallow.
However, for LVM, you can traceback from dm-6 to device with this handy one-liner: lvdisplay|awk '/LV Name/{n=$3} /Block device/{d=$3; sub(".*:","dm-",d); print d,n;}'
[1] iotop: http://guichaz.free.fr/iotop/ [2] iodump: http://www.xaprb.com/blog/2009/08/23/how-to-find-per-process-io-statistics-on-linux/