Can small writes generate a lot of faults?
Daniel Hilst Selli
danielhilst at gmail.com
Fri Apr 19 17:42:05 EDT 2013
My case is this, I'm using collectd [1] with rrdtool [2] to monitor some
server.
a) When I enable rrdtool plugin I can grab collectd process as top page
fault process on top command.
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ nFLT COMMAND
20128 root 18 0 4105m 35m 17m S 7.9 0.3 0:09.62 22k
/opt/collectd/sbin/collectd
b) Disabling rrdtool plugin dramastically decrease the number of page
faults of collectd.
c) I know that rrdtool plugin is known to generate a lot of small
writes, as stated in [3]. Also I know the parameters to improving
collectd's cache usage to save I/O, but this is not the question here..
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, ... !?
Is that possible?
Cheers,
[1] http://www.collectd.org
[2] http://oss.oetiker.ch/rrdtool/
[3] https://collectd.org/wiki/index.php/Inside_the_RRDtool_plugin
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