[rrd-developers] rrdcached performance problem

[kevin brintnall]

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
instructive.

-- 
 kevin brintnall =~ /kbrint at rufus.net/