Mark, > it's very simple: pagecache and VM balancing is a very important part of the > kernel, and has received a lot of quite productive attention over the years. > I question the assumption that "rebooting the pagecache" is a sensible way to > deal with memory-tuning problems. it seems very passive-aggressive to me: > as if there is assumption that the kernel isn't or can't Do The Right Thing > for HPC.
Sure, it's important - WITHIN a given job. Why should a new job's performance depend on what ran before? (And in most cases, the impact is negative, because the cached pages are not the ones needed by the new job.) > for sites where a single job is rolled onto all nodes and runs for a long > time, then is entirely removed, sure, it may make sense. rebooting entirely > might even work better. I'm mainly concerned with clusters which run a > wide mixture of jobs, probably with multiple jobs sharing a node at times. I would advise any user never to do that. > who says determinism is a good thing? I assume, for instance, you turn off > your CPU caches to obtain determinism, right? I'm not claiming that variance > is good, but why do you assume that the normal functioning of the pagecache > will cause it? Try it and see. Regards, Max _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
