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SubjectRe: [PATCH -mm 07/16] second chance replacement for anonymous pages
Rik van Riel wrote:
> On Wed, 28 May 2008 14:36:56 +0900
> Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
>
>>> /*
>>> + * Count the referenced anon pages as rotated, to balance pageout
>>> + * scan pressure between file and anonymous pages in get_sacn_ratio.
>>> + */
>>> + if (!file)
>>> + zone->recent_rotated_anon += pgmoved;
>>> +
>> Shouldn't 'pgmoved' be cleared to 0 before scanning l_hold?
>> It's used to store the result of sc->isolate_pages() before
>> scanning l_hold.
>
> It is zeroed 2 statements down.
>
> if (!file)
> zone->recent_rotated_anon += pgmoved;
>
> /*
> * Now put the pages back on the appropriate [file or anon] inactive
> * and active lists.
> */
> pagevec_init(&pvec, 1);
> pgmoved = 0;
>

When all the patches applied, shrink_active_list() looks like:

1135 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1136 ISOLATE_ACTIVE, zone,
1137 sc->mem_cgroup, 1, file);
:
1150 if (file)
1151 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1152 else
1153 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
1154 spin_unlock_irq(&zone->lru_lock);
1155
1156 while (!list_empty(&l_hold)) {
:
1166 if (page_referenced(page, 0, sc->mem_cgroup) && file) {
1167 /* Referenced file pages stay active. */
1168 list_add(&page->lru, &l_active);
1169 } else {
1170 list_add(&page->lru, &l_inactive);
1171 if (!file)
1172 /* Anonymous pages always get deactivated. */
1173 pgmoved++;
:
1178 }
1179 }
1180
1181 /*
1182 * Count the referenced anon pages as rotated, to balance pageout
1183 * scan pressure between file and anonymous pages in get_sacn_ratio.
1184 */
1185 if (!file)
1186 zone->recent_rotated_anon += pgmoved;

So, I wondered that there is no need to clear pgmoved before 1156 line.


Thanks,
Daisuke Nishimura.




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