* Linus Torvalds (torvalds@xxxxxxxxxxxxxxxxxxxx) wrote: > On Mon, Oct 29, 2012 at 5:42 AM, Mathieu Desnoyers > <mathieu.desnoyers@xxxxxxxxxxxx> wrote: > > > > So defining e.g.: > > > > #include <linux/log2.h> > > > > #define DFR_HASH_BITS (PAGE_SHIFT - ilog2(BITS_PER_LONG)) > > > > would keep the intended behavior in all cases: use one page for the hash > > array. > > Well, since that wasn't true before either because of the long-time > bug you point out, clearly the page size isn't all that important. I > think it's more important to have small and simple code, and "9" is > certainly that, compared to playing ilog2 games with not-so-obvious > things. > > Because there's no reason to believe that '9' is in any way a worse > random number than something page-shift-related, is there? And getting > away from *previous* overly-complicated size calculations that had > been broken because they were too complicated and random, sounds like > a good idea. Good point. I agree that unless we really care about the precise number of TLB entries and cache lines used by this hash table, we might want to stay away from page-size and pointer-size based calculation. It might not hurt to explain this in the patch changelog though. Thanks, Mathieu -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
