On Mon, Oct 10, 2011 at 12:20:53PM +0200, Richard Guenther wrote: > On Sun, Oct 9, 2011 at 9:55 PM, Andi Kleen <a...@firstfloor.org> wrote: > > From: Andi Kleen <a...@linux.intel.com> > > > > Add a threshold to avoid freeing pages back too early to the OS. > > This avoid virtual memory map fragmentation. > > > > Based on a idea from Honza > > Less than 20% looks high. Shouldn't ggc-free-min be enough to > avoid fragmentation?
It depends on the working set. If there's more to garbage collect than max(ggc-free-min, threshold*total) a host without MADV_DONTNEED will get holes. And ggc-free-min isn't very much on a large build. So it seems safer to me to have a threshold which adjusts for large working sets. What value do you prefer instead of 20%? (or just 0) > > This will hide gc bugs with always-collect (ggc-checking), so > the parameter(s) need to be adjusted for that case to always > give pages back. The current values should probably be printed > where the two existing ones are printed as well (with -v). Will fix. -Andi
