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 <[email protected]>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 > [email protected] > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > -- Gaurav Jain Associate Software Engineer VxVM Escalations Team, SAMG Symantec Software India Pvt. Ltd.
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