http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50636
--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-10-07 10:01:32 UTC --- (In reply to comment #2) > Perhaps on Linux, at least with recentish kernel, we could change > release_pages > into keeping the pages in the G.free_pages chain, but call madvise > MADV_DONTNEED on the pages (and remember that we've done that so next > release_pages won't do it again unless we have since then alloc_page'd it). > At > least on 64-bit hosts where there is plenty of address space. MADV_DONTNEED > will keep it around unless the kernel needs it for something else (something > e.g. glibc malloc uses too). Seems I misremembered what MADV_DONTNEED it, what I described was the proposed and unfortunately shot down MADV_FREE. MADV_DONTNEED zaps the pages immediately, so you get new zeroed pages even if it is touched immediately after the madvise call. Still, even MADV_DONTNEED is useful, it will prevent the excessive fragmentation.
