Re: [PATCH] mmtom: Prevent shrinking of active anon lru list in case of no swap space V2

[Minchan Kim <minchan.kim@gmail.com>]

On Thu, May 14, 2009 at 9:11 PM, KOSAKI Motohiro
<kosaki.motohiro@jp.fujitsu.com> wrote:
>> On Thu, May 14, 2009 at 8:44 PM, KOSAKI Motohiro
>> <kosaki.motohiro@jp.fujitsu.com> wrote:
>> >> >
>> >> > Changelog since V2
>> >> > ?o Add new function - can_reclaim_anon : it tests anon_list can be reclaim
>> >> >
>> >> > Changelog since V1
>> >> > ?o Use nr_swap_pages <= 0 in shrink_active_list to prevent scanning ?of active anon list.
>> >> >
>> >> > 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>
>> >>
>> >> looks good to me. thanks :)
>> >
>> > Grr, my fault.
>> >
>> >
>> >
>> >> ?static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
>> >> ? ? ? struct zone *zone, struct scan_control *sc, int priority)
>> >> ?{
>> >> @@ -1399,7 +1412,7 @@ static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
>> >> ? ? ? ? ? ? ? return 0;
>> >> ? ? ? }
>> >>
>> >> - ? ? if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
>> >> + ? ? if (lru == LRU_ACTIVE_ANON && can_reclaim_anon(zone, sc)) {
>> >> ? ? ? ? ? ? ? shrink_active_list(nr_to_scan, zone, sc, priority, file);
>> >> ? ? ? ? ? ? ? return 0;
>> >
>> > you shouldn't do that. if nr_swap_pages==0, get_scan_ratio return anon=0%.
>> > then, this branch is unnecessary.
>> >
>>
>> But, I think at last it can be happen following as.
>>
>> 1515         * Even if we did not try to evict anon pages at all, we want to
>> 1516         * rebalance the anon lru active/inactive ratio.
>> 1517         */
>> 1518        if (inactive_anon_is_low(zone, sc))
>> 1519                shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
>
> I pointed to shrink_list(), but you replayed shrink_zone().
> I only talked about shrink_list().
>

In shrink_zone, we call get_scan_ratio. it prevent scanning anon list.
but, in shrink_all_zones can't prevent it.

Also,  I think shrink_list is not hot patch.
So check of one condition adding is trivial

If I don't understand your point, please explain detaily


-- 
Kinds regards,
Minchan Kim

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