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SubjectRe: [PATCH] Prevent shrinking of active anon lru list in case of no swap space
On Thu, 14 May 2009 16:19:52 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:

> >
> > Now shrink_active_list is called several places.
> > But if we don't have a swap space, we can't reclaim anon pages.
> > So, we don't need deactivating anon pages in anon lru list.
> >
> > Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
> > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > Cc: Johannes Weiner <hannes@cmpxchg.org>
> > Cc: Rik van Riel <riel@redhat.com>
>
> hm, The analysis seems right. but
>
> In general branch should put into non frequency path.
> why caller modification as following patch is wrong?

Yes. You're right. Firstly I though that.
But there are a few place where inactve_anon_is_low is called.
In addition to it, we always have to call with (nr_swap_pages <= 0) with it.
So alone inactive_anon_is_low is lost function's meaning.

I think it's meaningless.
But We can improve one function wrapper.

/* I can't be remind proper function name. Can you suggest me ? */
if (do_we_have_to_shrink_list(zone, &sc))


int do_we_have_to_shrink_list(...)
{
if (inactive_anon_is_low(zone, &sc) && (nr_swap_pages <= 0))

}

What do you think ?

>
> /*
> * Do some background aging of the anon list, to give
> * pages a chance to be referenced before reclaiming.
> */
> - if (inactive_anon_is_low(zone, &sc))
> + if (inactive_anon_is_low(zone, &sc) && (nr_swap_pages <= 0))
> shrink_active_list(SWAP_CLUSTER_MAX, zone,
> &sc, priority, 0);
>
>
>
>
> > ---
> > mm/vmscan.c | 6 ++++++
> > 1 files changed, 6 insertions(+), 0 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 2f9d555..e4d71f4 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1238,6 +1238,12 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
> > enum lru_list lru;
> > struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
> >
> > + /*
> > + * we can't shrink anon list in case of no swap space.
> > + */
> > + if (file == 0 && nr_swap_pages <= 0)
> > + return;
> > +
> >
> > lru_add_drain();
> > spin_lock_irq(&zone->lru_lock);
> > pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
> > --
> > 1.5.4.3
> >
> >
> > --
> > Kinds Regards
> > Minchan Kim
>
>
>


--
Kinds Regards
Minchan Kim


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