Page-faults by a process on writing OR reading are really not that different. In both cases, an attempt is made to read the physical address (corresponding to the virtual address) from the page-table BEFORE the *read *or *write *machine level instructions are executed. So, if the address to which writes (or reads) are being performed, does not have a valid page-table entry ie. a valid virtual address, a page-fault will be triggered. Best Regards Gaurav Jain On Fri, Apr 19, 2013 at 11:42 PM, Daniel Hilst Selli <danielhilst@gmail.com>wrote:
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
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
-- Gaurav Jain Associate Software Engineer VxVM Escalations Team, SAMG Symantec Software India Pvt. Ltd.