On Mon, Apr 22, 2013 at 01:49:39PM +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> > > > > WPA can spend a lot of time just resizing the type merging hash tables. > > This adds experimental --params to size them large initially. On my large > > LTO build I get a 1.1% improvement in build time from presizing the hash > > tables to a large enough value. > > With what values? Certainly we will have at least as many hashes
For the test I used just the final values from -flto-report from a previous run. I know it's cheating. But it's reasonable to just always use a large table, unless someone comes up with a nice way to pre estimate. > as types, so increasing the hash cache sizes to the size of the types > (thus use the same --param) would be obvious. Likewise there will iirc the caches were usually smaller than the types from lto-report. Perhaps they have less collisions. -Andi
