On Mon, Apr 22, 2013 at 5:42 PM, Andi Kleen <a...@linux.intel.com> wrote: > On Mon, Apr 22, 2013 at 01:46:58PM +0200, Richard Biener wrote: >> On Fri, Apr 19, 2013 at 11:31 PM, Andi Kleen <a...@firstfloor.org> wrote: >> > From: Andi Kleen <a...@linux.intel.com> >> > >> > For a large LTO test case The previous pointer hash change brought >> > the collision rate for the WPA gimple type hash table from 90% to >> > 70. This patch uses the well known murmur3 to improve it further >> > to 64%. >> >> But if they are pointers then pointer_hash should be good enough... ? > > The original pointer hash (ptr >> 3) % hashsize and throwing away most bits is > very poor. > > The evahash based on I sent earlier is better, but murmur3 is even better than > that, at least for this case.
I'd rather not have different pointer hashes for things where there isn't a fundamental difference between the pointer values. Richard. > -Andi >
