Messages in this thread | | | Date | Thu, 27 Nov 2014 15:47:25 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH v17 1/7] mm: support madvise(MADV_FREE) |
| |
[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@gmail.com> > Cc: Linux API <linux-api@vger.kernel.org> > Cc: Hugh Dickins <hughd@google.com> > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > Cc: Mel Gorman <mgorman@suse.de> > Cc: Jason Evans <je@fb.com> > Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Acked-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com> > Acked-by: Rik van Riel <riel@redhat.com> > Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz> [...] -- Michal Hocko SUSE Labs
| |