[rrd-developers] rrdcached performance problem

kevin brintnall kbrint at rufus.net
Fri Oct 30 17:57:44 CET 2009

On Fri, Oct 30, 2009 at 09:47:43AM -0700, Thorsten von Eicken wrote:
> > What's the start time on that daemon?  If it was started slightly before
> > the graphs (~21:30-21:35), then it's possible that the CPU increase is
> > associated with the first flush (-f).
> >   
> It was right at the start of the graphs. If you look at the 
> "write-data_sets" graph, you can see very clearly how the flushing 
> starts at 22:38-22:39 and the first hour of flushing ends 23:46-23:47. 
> The cpu spike starts to build at 23:26-23:28 so it's not on a clean 
> boundary at all.If you look at the if-packets graph you can see how 
> inbound traffic is 100% stable throughout the whole run.

OK..  That's what I thought :|

> > Something is queueing a lot of files; I would only expect that to
> > result from the flush process if writing had stopped for a set of your
> > RRDs.  For example, if you have a large number of RRD files in the
> > journal that aren't being re-written afterwards, then the first flush
> > would contain all those.

When the queue length jumps up, try issuing the "QUEUE" command to the
daemon.  Maybe the list of queued files (or their order) will be

 kevin brintnall =~ /kbrint at rufus.net/

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