On Mon, Mar 30, 2009 at 02:27:12PM +0200, Nick Piggin wrote: > It's interesting. I suspect that with the size of the dcache hash, > if we assume pretty random distribution of access patterns, then > it might be unlikely to get much common cache lines (ok, birthday The problem is that you increase the cache foot print overall because these hash tables are gigantic. And because it's random there will not be much locality. That is your hash table might still fit when you're lucky, but then if the rest of your workload needs a lot of cache too you might end up with a cache miss on every access. False sharing is not the issue with the big lock hash typically, that was more as an issue for a potential separate hash table design (I guess my original sentence was a bit confusing) BTW the alternative would be to switch the hash table to some large fan out tree indexed by the string hash value and then use the standard lockless algorithms on that. -Andi -- ak@xxxxxxxxxxxxxxx -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
