[rrd-developers] rrdcached performance problem
kbrint at rufus.net
Sat Oct 31 21:14:19 CET 2009
> It's pretty clear that the performance when operating in memory is very
> nice and smooth, but when memory is exceeded things become bumpy. It
> degrades nicely and recovers well: I saw 9k queue items at one point and
> that got worked off over close to an hour but did work itself out as
> opposed to spinning out of control.
9k/hour seems awfully slow. Even my old development box can flush
55k/hour. Maybe more entries are being enqueued at the same time...
> What value of -m do you suggest? -w divided by step size?
That's the maximum; any more than that is just waste. IIRC you had around
~400 cached values per RRD file. So, if you use '-m 400' you'll only have
call realloc() one time. However, the 401st value will cause a large
The ideal value is highly dependent on your malloc() implementation.. I
would start with a power of two large enough to get you relatively few
realloc() but small enough that you don't waste too much... In your case,
maybe '-m 64'.
kevin brintnall =~ /kbrint at rufus.net/
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