mm/madvise.c: free swp_entry in madvise_free

When I test below piece of code with 12 processes(ie, 512M * 12 = 6G
consume) on my (3G ram + 12 cpu + 8G swap, the madvise_free is
siginficat slower (ie, 2x times) than madvise_dontneed.

     loop = 5;
     mmap(512M);
     while (loop--) {
             memset(512M);
             madvise(MADV_FREE or MADV_DONTNEED);
     }

The reason is lots of swapin.

1) dontneed: 1,612 swapin
2) madvfree: 879,585 swapin

If we find hinted pages were already swapped out when syscall is called,
it's pointless to keep the swapped-out pages in pte.  Instead, let's
free the cold page because swapin is more expensive than (alloc page +
zeroing).

With this patch, it reduced swapin from 879,585 to 1,878 so elapsed time

1) dontneed: 6.10user 233.50system 0:50.44elapsed
2) madvfree: 6.03user 401.17system 1:30.67elapsed
2) madvfree + below patch: 6.70user 339.14system 1:04.45elapsed

Signed-off-by: Minchan Kim <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Shaohua Li <[email protected]>
Cc: <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Chen Gang <[email protected]>
Cc: Chris Zankel <[email protected]>
Cc: Daniel Micay <[email protected]>
Cc: Darrick J. Wong <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Ivan Kokshaysky <[email protected]>
Cc: Jason Evans <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Mika Penttil <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Richard Henderson <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Roland Dreier <[email protected]>
Cc: Russell King <[email protected]>
Cc: Shaohua Li <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Wu Fengguang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions