On Thu, Jan 28, 2016 at 08:16:25AM +0100, Michael Kerrisk (man-pages) wrote: > Hello Minchan, > > On 11/30/2015 07:39 AM, Minchan Kim wrote: > > In v4, Andrew wanted to settle in old basic MADV_FREE and introduces > > new stuffs(ie, lazyfree LRU, swapless support and lazyfreeness) later > > so this version doesn't include them. > > > > I have been tested it on mmotm-2015-11-25-17-08 with additional > > patch[1] from Kirill to prevent BUG_ON which he didn't send to > > linux-mm yet as formal patch. With it, I couldn't find any > > problem so far. > > > > Note that this version is based on THP refcount redesign so > > I needed some modification on MADV_FREE because split_huge_pmd > > doesn't split a THP page any more and pmd_trans_huge(pmd) is not > > enough to guarantee the page is not THP page. > > As well, for MAVD_FREE lazy-split, THP split should respect > > pmd's dirtiness rather than marking ptes of all subpages dirty > > unconditionally. Please, review last patch in this patchset. > > Now that MADV_FREE has been merged, would you be willing to write > patch to the madvise(2) man page that describes the semantics, > noes limitations and restrictions, and (ideally) has some sentences > describing use cases? > Hello Michael, Could you review this patch? Thanks. >From 203372f901f574e991215fdff6907608ba53f932 Mon Sep 17 00:00:00 2001 From: Minchan Kim <minchan@xxxxxxxxxx> Date: Fri, 5 Feb 2016 11:09:54 +0900 Subject: [PATCH] madvise.2: Add MADV_FREE Document the MADV_FREE flags added to madvise() in Linux 4.5 Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> --- man2/madvise.2 | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/man2/madvise.2 b/man2/madvise.2 index c1df67c..4704304 100644 --- a/man2/madvise.2 +++ b/man2/madvise.2 @@ -143,6 +143,25 @@ flag are special memory areas that are not managed by the virtual memory subsystem. Such pages are typically created by device drivers that map the pages into user space.) +.TP +.B MADV_FREE " (since Linux 4.5)" +Application is finished with the given range, so kernel can free +resources associated with it but the freeing could be delayed until +memory pressure happens or canceld by write operation by user. + +After a successful MADV_FREE operation, user shouldn't expect kernel +keeps stale data on the page. However, subsequent write of pages +in the range will succeed and then kernel cannot free those dirtied pages +so user can always see just written data. If there was no subsequent +write, kernel can free those clean pages any time. In such case, +user can see zero-fill-on-demand pages. + +Note that, it works only with private anonymous pages (see +.BR mmap (2)). +On swapless system, freeing pages in given range happens instantly +regardless of memory pressure. + + .\" .\" ====================================================================== .\" -- 1.9.1 -- 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>