[Beowulf] [OOM killer/scheduler] disabling swap on cluster nodes?

[Prentice Bisbal]

On 02/10/2015 02:02 PM, Mark Hahn wrote:
>> ?Do you know if remote swap is working well now? I remember it 
>> working not
>> so good because it's a difficult problem, but I haven't tested it 
>> lately.?
>
> I suspect remote swap works better now, in part because systems have 
> been moving more towards specialized allocators.  (motivated by wanting
> to scale-per-core, for instance.)  it was always possible to make 
> network-swap robust: all it takes is enough partitioning of storage 
> pools, so that you don't run into an allocation-swap-allocation gotcha.
>
> 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...
Sometimes it can be faster than disk I/O. Some SANs have massive amounts 
of cache, so that data  you've 'swapped to disk' might still be in the 
SANs cache. I doubt this would be the case in a large cluster, but I've 
seen and measured this effect first hand.

However, for HPC, I would think swapping to a network disk would 
introduce some of the performance hits we're trying to avoid, like disk 
latency, and add network latency on top of that.

--
Prentice