> Eadline's Law : Cache is only good the second time. Hmm, that’s why they have all those clever pre-fetchers which try to guess your memory access patterns and predict what's going to be needed next. (Your choice whether you read “clever” in a cynical voice or not :-)) *IF* that works, then the cache is useful the first time. If not, then they can mess things up royally by evicting stuff that you did want there.
> On 19 Sep 2021, at 12:02, John Hearns <hear...@gmail.com> wrote: > > Eadline's Law : Cache is only good the second time. > > On Fri, 17 Sep 2021, 21:25 Douglas Eadline, <deadl...@eadline.org > <mailto:deadl...@eadline.org>> wrote: > --snip-- > > > > Where I disagree with you is (3). Whether or not cache size is important > > depends on the size of the job. If your iterating through data-parallel > > loops over a large dataset that exceeds cache size, the opportunity to > > reread cached data is probably limited or nonexistent. As we often say > > here, "it depends". I'm sore someone with better low-level hardware > > knowledge will pipe in and tell me why I'm wrong (Cunningham's Law). > > > > Of course it all depends. However, as core counts go up, a > fixed amount of cache must get shared. Since the high core counts > are putting pressure on main memory BW, cache gets more > important. This is why AMD is doing V-cache for new processors. > Core counts have outstripped memory BW, their solution > seems to be big caches. And, cache is only good the second time :-) > > > -- big snip-- > > -- > Doug > > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org <mailto:Beowulf@beowulf.org> > sponsored by Penguin Computing > To change your subscription (digest mode or unsubscribe) visit > https://beowulf.org/cgi-bin/mailman/listinfo/beowulf > <https://beowulf.org/cgi-bin/mailman/listinfo/beowulf> > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing > To change your subscription (digest mode or unsubscribe) visit > https://beowulf.org/cgi-bin/mailman/listinfo/beowulf -- Jim James Cownie <jcow...@gmail.com> Mob: +44 780 637 7146
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