]> pilppa.com Git - linux-2.6-omap-h63xx.git/commit
mm: add comment why mark_page_accessed() would be better than pte_mkyoung() in follow...
authorKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Tue, 31 Mar 2009 22:19:37 +0000 (15:19 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 1 Apr 2009 15:59:12 +0000 (08:59 -0700)
commitbd775c42ea5f7c766d03a287083837cf05e7e738
tree40084f399068bed56c3061afd5e1175c679160df
parent9786bf841da57fac3457a1dac41acb4c1f2eced6
mm: add comment why mark_page_accessed() would be better than pte_mkyoung() in follow_page()

At first look, mark_page_accessed() in follow_page() seems a bit strange.
It seems pte_mkyoung() would be better consistent with other kernel code.

However, it is intentional. The commit log said:

    ------------------------------------------------
    commit 9e45f61d69be9024a2e6bef3831fb04d90fac7a8
    Author: akpm <akpm>
    Date:   Fri Aug 15 07:24:59 2003 +0000

    [PATCH] Use mark_page_accessed() in follow_page()

    Touching a page via follow_page() counts as a reference so we should be
    either setting the referenced bit in the pte or running mark_page_accessed().

    Altering the pte is tricky because we haven't implemented an atomic
    pte_mkyoung().  And mark_page_accessed() is better anyway because it has more
    aging state: it can move the page onto the active list.

    BKrev: 3f3c8acbplT8FbwBVGtth7QmnqWkIw
    ------------------------------------------------

The atomic issue is still true nowadays. adding comment help to understand
code intention and it would be better.

[akpm@linux-foundation.org: clarify text]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/memory.c