Subject: Re: disk write instrumentation
To: Wolfgang Rupprecht <email@example.com>
From: Thor Lancelot Simon <firstname.lastname@example.org>
Date: 03/10/2001 14:31:57
On Sat, Mar 10, 2001 at 11:27:23AM -0800, Wolfgang Rupprecht wrote:
> Is there an easy way to instrument disk IO in -current so one can tell
> who is writing what?
> I just put a new disk into my laptop. Even though the new disk is
> slightly lower power, it manages to put all that energy into acoustic
> radiation. The disk-seeks are annoyingly loud.
> I've already turned on "noatime, nodevmtime, softdeps" and I still get
> a some disk io every few minutes. I'm not running whois or anything
> inherently noisy like that, but I do have cron, syslog, ntpd, amd,
> Xdm. How do I find the villian short of exhaustive search by killing
> one daemon at a time?
I've had this problm on a laptop recently where I've been trying to keep
the disk spun down. I think that some change that came in with the softdep
code (the smooth-syncer perhaps?) is causing periodic writes even if *no*
file in the filesystem is open for writing, even if the filesystem is not
mounted "softdep". I say this because after looking at open files with
fstat and even resorting to killing off daemons, I can't keep the damned
disk in my new ThinkPad spun down for 30 seconds.
Actually, I guess it doesn't *have* to be writes. It could be reads -- but
I still can't find any userland process generating them. I'm not using any
swap (I have it, but it always shows up as 0% used) either. Grrr.