[Beowulf] [OOM killer/scheduler] disabling swap on cluster nodes?
hahn at mcmaster.ca
Tue Feb 10 21:25:58 PST 2015
>> is net-swap really ever a good idea? it always seems like asking for
>> trouble, though in principle there's no reason why net IO should be
>> "worse" than disk IO...
> ... except for the need to allocate memory to build packets to send the swap
I thought the implication was clear, that doing disk IO may also
require memory allocations.
> There are still a few places that look at you funny if you suggest running
> w/o swap. The 6 orders of magnitude performance difference for random page
> touching performance suggests you should stare them back down.
absolutely: if you have reason to believe all your pages are uniformly hot,
more power to you!
> Seriously, if you can avoid under-spec'ing/provisioning ram, you should.
in other words: buy extra ram to hold your cold pages! after all, dram
is only O($10/GB), and disk is O($0.05/GB). oh, wait...
> wish for the wild west of OOM shooting random things in comparison to random
> 4k page touches. Yes, I've seen the latter.
thrashing is bad. it's not the same as *using* swap. that's why swap
still makes sense.
interesting thought: SSD is about $0.5/GB, so would make a great swap dev -
has anyone tried tuning the swap cluster size to match the SSD flash block?
More information about the Beowulf