On 2017.04.09 at 21:10 +0200, Markus Trippelsdorf wrote: > On 2017.04.09 at 21:25 +0300, Alexander Monakov wrote: > > On Sun, 9 Apr 2017, Markus Trippelsdorf wrote: > > > > > The minimum size heuristic for the garbage collector's heap, before it > > > starts collecting, was last updated over ten years ago. > > > It currently has a hard upper limit of 128MB. > > > This is too low for current machines where 8GB of RAM is normal. > > > So, it seems to me, a new upper bound of 1GB would be appropriate. > > > > While amount of available RAM has grown, so has the number of available CPU > > cores (counteracting RAM growth for parallel builds). Building under a > > virtualized environment with less-than-host RAM got also more common I > > think. > > > > Bumping it all the way up to 1GB seems excessive, how did you arrive at that > > figure? E.g. my recollection from watching a Firefox build is that most of > > compiler instances need under 0.5GB (RSS). > > 1GB was just a number I've picked to get the discussion going. > And you are right, 512MB looks like a good compromise. > > > > Compile times of large C++ projects improve by over 10% due to this > > > change. > > > > Can you explain a bit more, what projects you've tested?.. 10+% looks > > surprisingly high to me. > > I've checked LLVM build times on ppc64le and X86_64.
Here are the ppc64le numbers (llvm+clang+lld Release build): --param ggc-min-heapsize=131072 : ninja -j60 15951.08s user 256.68s system 5448% cpu 4:57.46 total --param ggc-min-heapsize=524288 : ninja -j60 14192.62s user 253.14s system 5527% cpu 4:21.34 total -- Markus
