Date: Sat, 8 Mar 2008 22:23:29 +0000 (GMT) From: Robert Watson <rwatson@FreeBSD.org> To: Steven Hartland <killing@multiplay.co.uk> Cc: freebsd-performance@freebsd.org Subject: Re: rrdtool / mtr causing stalling on 7.0 Message-ID: <20080308221441.E11432@fledge.watson.org> In-Reply-To: <056601c8814c$516c0370$b6db87d4@multiplay.co.uk> References: <056601c8814c$516c0370$b6db87d4@multiplay.co.uk>
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On Sat, 8 Mar 2008, Steven Hartland wrote:
> We've been suffering on our stats box for some time now where by the machine
> will just stall for several seconds preventing everything from tab
> completion to vi newfile.txt.
>
> I was hoping an upgrade to 7.0 and ULE may help the situation but
> unfortunately it hasn't.
>
> I've attached both dmesg and output from lock profiling during a 5 minute
> period where I know the stall happened at least once.
>
> Any advice / pointers would be gratefully received.
It looks like the attachment got lost on the way through the mailing list.
I think the first starting point is: what sort of stall is this? Is it, for
example, all network communication stalling, all disk I/O stalling, or the
entire kernel and all processes stalling? The usual diagnostics are:
- Does the machine stop responding to pings while stalled, and/or possibly
"catch up" all at once when it recovers?
- If you run the following loop on the machine without any network or console
I/O, do you see gaps in time stamps:
while (1) {
sleep 1
date >> date.log
}
- If you write a short C program that looks a lot like the above loop, but
logs time stamps into an in-memory buffer, and have it look for gaps in the
sequence of >3 seconds, does it run across the stall?
Robert N M Watson
Computer Laboratory
University of Cambridge
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