[rrd-developers] Rrdtool fetch performance difference between Linux and Freebsd

[Tobias Oetiker]

Hi Tugrul,

Today Tugrul Erdogan wrote:

> Hi,
>
> I am porting a project which is developed and used on FreeBSD 10 to Linux.
> After porting rrdtool funuctionalities, I realized that periodic "rrdtool
> fetch" calls on CentOS 7 spends two times more time than on FreeBSD. The
> rrdtool version on FreeBSD is 1.4.7 and on Linux 1.4.8 .
>
> To examine the situation more deeply, I have transfer same rrd file to
> FreeBSD and I have write a bash script which reports start and end times of
> 500 "rrdtool fetch" call with same parameters on same rrd file. The results
> show that "rrdtool fetch" call on Linux is two times slower than "rrdtool
> fetch" call on Linux.
>
> What can be the cause of this performance decreasing? How can I improve the
> perfomance of "rrdtool fetch" call on Linux to make it as fast as FreeBSD
> "rrdtool fetch" call performance?

hmmm so you should make sure to use the same version on both
systems AND also make sure they are both compiled with mmap io (or
both not) and make sure that other reference benchmarks show the
same results between the two systems ... (equal cpu, ram and disk)

then I would use some profiler like cachegrind for example to
see where the performance is lost ... if you find a way to speedup
the linux version fetch by a factor of two that would be great!

cheers
tobi


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Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
www.oetiker.ch tobi at oetiker.ch +41 62 775 9902