Granger wrote:Does it read or does it write? And if it is writes, what kind of data (maps, players, whatever else you persist)?
The situation is a bit mysterious, because it's not like the system is "saturated" with I/O in some meaningful manner, from what I can tell. I'm very far from sure exactly what the problem is (it's quite hard to reproduce in an environment where I can properly debug it), but I strongly get the feeling that the a core part of the problem is sync-related. I really have no idea where in the storage stack the problem occurs, but I get the strong impression that whenever a process runs any sync/fsync/fdatasync operation, that causes all other system I/O to be congested. I'm not sure that describes the entirety of the problem either, though; I generally get the feeling that many operations that should be possible to do in the page cache block unnecessarily here and there.
Either way, the general problem is not so much about I/O bandwidth as it is about I/O latency, and that's where I expect SSDs to make an impact.