Accessing RAM sometimes costs extra log(N)

arxiv.org

50 pointsTojot3 comments

In response to "The Myth of RAM" https://news.ycombinator.com/item?id=12383012

It so happens that a large part of my PhD was on this very subject. The result I've got N log(N), this is more visible when you get to larger RAM (I had 0,5 TB RAM at the time). We have an empirical result, a justification and a rigorous predictive model.

The reason has to do with hashing, but a different type: TLB.

Feel free to take a look at a free copy at http://arxiv.org/abs/1212.0703 where we establish the VAT cost model.

Very interesting and informative. I would have expected a TLB to incur an additional cost beyond exhausting the cache hierarchy. But, I would have expected it to be a single additional cliff around a gig at most.

Shame there's no discussion here. I've x-posted to https://www.reddit.com/r/programming/comments/509qhd/randoml... Maybe that will drum up a bit more conversation.

Thanks! Looks like it worked.

Reply on news.ycombinator.com