On 8/1/2013 2:08 PM, Roman Chyla wrote:
Hi, here is a short post describing the results of the yesterday run with
added parameters as per Shawn's recommendation, have fun getting confused ;)
http://29min.wordpress.com/2013/08/01/measuring-solr-performance-ii/
I am having a very difficult time with the graphs. I have no idea what
I'm looking at. The graphs are probably self-explanatory to you,
because you created them and you've been staring at them for hours.
There are both lines and shaded areas, and I can't tell what they mean.
Tables with numbers, if they have a good legend, would be awesome.
One thing I'd like to see, and when I have some time of my own I will do
some comprehensive long-term comparisons on production systems, is to
see what adding or changing *one* GC tuning parameter at a time does, so
I can find the ideal settings and have some idea of which settings make
the most difference.
My concern with garbage collection tuning has been mostly worst-case
scenario pauses. I certainly do want averages to come down, but it's
really the worst-case that concerns me.
Let's say that one of my typical queries takes 100 milliseconds on
average with my GC config. Somebody comes up with another GC config
that makes the same query take 25 milliseconds or less on average. If
that config also results in rare stop-the-world garbage collections that
take 5 full seconds, I won't be using it. I'd rather deal with the
slower average queries than the GC pause problems.
I had to let my production systems run for days with jHiccup before I
really noticed that I had a GC pause problem. I've since learned that
if I look at GC logs with GCLogViewer, I can get much the same information.
Thanks,
Shawn
