On Wed, Feb 11, 2015 at 3:01 PM, Jason Riedy <[email protected]> wrote: > You know all those system daemons that aren't doing anything while a > compute job is running? Those get pushed out to swap if the thing > doing real work needs the memory. They are swapped back into memory > between jobs (ideally not during).
How many hundreds of daemons are running and how many hundreds of GB of RAM do they use on the compute nodes? Of course, I'm exaggerating here, but seriously speaking only a handful of small daemons are enough. Now if you think about a cron daemon, this will wake up every minute to check whether it has stuff to do, so every minute the swap will be exercised. A queueing system daemon often send usage/accounting data to the master node on seconds to tens of seconds time scale, so also not a good match for swap. A Nagios/ganglia/zabbix/etc. daemon does the same. So what are the daemons that can stay swapped out for longer periods? And are these daemons using so much memory? Are we really talking about setting up multi-GB swap for a few MB or tens of MB of daemon code and data? My first generation Raspberry Pi (512MB RAM) does all a node should do and much more - before touching swap. > It'd be nice simply not to have those daemons or to force them into > out-of-memory hibernation, but that's much more effort. I don't quite understand, why are the daemons started at all if they are not needed? > (Also, it'd > be nice for boot times on 1+TiB nodes to be less than 15 minutes > before even touching the OS. ugh. If only there were a fast scan > of a small portion where the OS will be loaded, then the OS could > scan the rest...) Agreed. For a 4TB machine it's really ridiculous... Cheers, Bogdan _______________________________________________ Beowulf mailing list, [email protected] sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
