[collectd] [rrd-users] Can small writes generate a lot of faults?

Tobi Oetiker tobi at oetiker.ch
Sat Apr 20 14:09:43 CEST 2013

hi daniel

On 19.04.2013, at 16:42, Daniel Hilst Selli <danielhilst at gmail.com> wrote:

> AFAIK, major page faults are generated when data that is not yet present 
> on RAM is loaded from disk, but in this case data is being write do 
> disk, I can't
> see how writes can generate faults, but still, it seems that is 
> happening, ... !?

rrdtool changes just few bytes in the rrf file with each update

the OS though can only write a complete block of data to disk.

so when you write a byte to a file, the OS has to first fetch the block, modify the byte and write the block back

that is why rrdtool benefits greatly from more RAM as it can hold mor blocks in RAM and does not have to read them first.

cheers tobi

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