On Thu, Jun 09, 2011 at 02:59:02PM +0100, Mel Gorman wrote:
> On Tue, Jun 07, 2011 at 11:38:16PM +0900, Minchan Kim wrote:
> > There are some places to isolate lru page and I believe
> > users of isolate_lru_page will be growing.
> > The purpose of them is each different so part of isolated pages
> > should put back to LRU, again.
> >
> > The problem is when we put back the page into LRU,
> > we lose LRU ordering and the page is inserted at head of LRU list.
> > It makes unnecessary LRU churning so that vm can evict working set pages
> > rather than idle pages.
> >
> > This patch adds new modes when we isolate page in LRU so we don't isolate pages
> > if we can't handle it. It could reduce LRU churning.
> >
> > This patch doesn't change old behavior. It's just used by next patches.
> >
> > Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> > Cc: Mel Gorman <mgorman@xxxxxxx>
> > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> > Acked-by: Rik van Riel <riel@xxxxxxxxxx>
> > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> > Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx>
> > ---
> > include/linux/swap.h | 2 ++
> > mm/vmscan.c | 6 ++++++
> > 2 files changed, 8 insertions(+), 0 deletions(-)
> >
> > diff --git a/include/linux/swap.h b/include/linux/swap.h
> > index 48d50e6..731f5dd 100644
> > --- a/include/linux/swap.h
> > +++ b/include/linux/swap.h
> > @@ -248,6 +248,8 @@ enum ISOLATE_MODE {
> > ISOLATE_NONE,
> > ISOLATE_INACTIVE = 1, /* Isolate inactive pages */
> > ISOLATE_ACTIVE = 2, /* Isolate active pages */
> > + ISOLATE_CLEAN = 8, /* Isolate clean file */
> > + ISOLATE_UNMAPPED = 16, /* Isolate unmapped file */
> > };
>
> This really should be a bitwise type like gfp_t.
Agree. As I said, I will change it.
>
> >
> > /* linux/mm/vmscan.c */
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 4cbe114..26aa627 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -990,6 +990,12 @@ int __isolate_lru_page(struct page *page, enum ISOLATE_MODE mode, int file)
> >
> > ret = -EBUSY;
> >
> > + if (mode & ISOLATE_CLEAN && (PageDirty(page) || PageWriteback(page)))
> > + return ret;
> > +
> > + if (mode & ISOLATE_UNMAPPED && page_mapped(page))
> > + return ret;
> > +
> > if (likely(get_page_unless_zero(page))) {
> > /*
> > * Be careful not to clear PageLRU until after we're
>
> This patch does notuse ISOLATE_CLEAN or ISOLATE_UMAPPED anywhere. While
> I can guess how they will be used, it would be easier to review if one
> patch introduced ISOLATE_CLEAN and updated the call sites where it was
> relevant. Same with ISOLATE_UNMAPPED.
Totally agree.
I also always wanted it to others. :(
>
> Also when using & like this, I thought the compiler warned if it wasn't
> in parenthesis but maybe that's wrong. The problem is the operator
My compiler(gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5) was smart.
> precedence for bitwise AND and logical AND is easy to forget as it's
> so rarely an issue.
I will update the part for readability as well as compiler warning unexpected
>
> i.e. it's easy to forget if
>
> mode & ISOLATE_UNMAPPED && page_mapped(page)
>
> means
>
> mode & (ISOLATE_UNMAPPED && page_mapped(page))
>
> or
>
> (mode & ISOLATE_UNMAPPED) && page_mapped(page)
>
> Be nice and specific for this one.
>
> --
> Mel Gorman
> SUSE Labs
--
Kind regards
Minchan Kim
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