[Late but I didn't get to this soone - I hope this is still up-to-date version] On Mon 20-10-14 19:11:58, Minchan Kim wrote: > Linux doesn't have an ability to free pages lazy while other OS > already have been supported that named by madvise(MADV_FREE). > > The gain is clear that kernel can discard freed pages rather than > swapping out or OOM if memory pressure happens. > > Without memory pressure, freed pages would be reused by userspace > without another additional overhead(ex, page fault + allocation > + zeroing). > > How to work is following as. > > When madvise syscall is called, VM clears dirty bit of ptes of > the range. If memory pressure happens, VM checks dirty bit of > page table and if it found still "clean", it means it's a > "lazyfree pages" so VM could discard the page instead of swapping out. > Once there was store operation for the page before VM peek a page > to reclaim, dirty bit is set so VM can swap out the page instead of > discarding. Is there any patch for madvise man page? I guess the semantic will be same/similar to FreeBSD: http://www.freebsd.org/cgi/man.cgi?query=madvise&sektion=2 I guess the changelog should be more specific that this is only for the private MAP_ANON mappings (same applies to the patch for man). > Firstly, heavy users would be general allocators(ex, jemalloc, > tcmalloc and hope glibc supports it) and jemalloc/tcmalloc already > have supported the feature for other OS(ex, FreeBSD) > [...] > > Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx> > Cc: Linux API <linux-api@xxxxxxxxxxxxxxx> > Cc: Hugh Dickins <hughd@xxxxxxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > Cc: Mel Gorman <mgorman@xxxxxxx> > Cc: Jason Evans <je@xxxxxx> > Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Acked-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx> > Acked-by: Rik van Riel <riel@xxxxxxxxxx> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> Reviewed-by: Michal Hocko <mhocko@xxxxxxx> [...] -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>