Satyam Sharma wrote:
Hi Bill,
On 5/29/07, Bill Davidsen <[email protected]> wrote:
I recently noted that my system was spending a lot of time in i/o wait
when doing some tasks which I thought didn't involve i/o, as noted by
the lack of disk light activity most of the time. I thought of network,
certainly the NIC had no activity for this job. So I set up a little
loop to capture all disk i/o and network activity (including loopback).
That was no obvious help, and the program doesn't use pipes.
At this point I'm really curious, does someone have a good clue?
Note: I don't think this is a bug or performance issue, unless the
kernel is doing something and charging time to iowait instead of system
I don't see anything to fix, but I would like to understand.
What tool / kernel instrumentation / mechanism are you using to
determine that some task(s) are indeed blocked waiting for i/o? Perhaps
some userspace process accounting tools could be "broken" in the sense
that they generalize all uninterruptible sleep as waiting for i/o ...
I wouldn't expect /proc/stat and similar to be broken in that way, but
If no one has a better idea I guess I will assume there's a check needed
of where time is added to iowait. I was hoping to avoid a full kernel
search. Never thought of /proc data as a user space tool, but I guess.
--
Bill Davidsen <[email protected]>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
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