> @@ -1319,6 +1322,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> struct list_head *src = &lruvec->lists[lru];
> unsigned long nr_taken = 0;
> unsigned long scan;
> + LIST_HEAD(pages_skipped);
>
> for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
> struct page *page;
> @@ -1329,6 +1333,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>
> VM_BUG_ON_PAGE(!PageLRU(page), page);
>
> + if (page_zone_id(page) > sc->reclaim_idx)
> + list_move(&page->lru, &pages_skipped);
> +
> switch (__isolate_lru_page(page, mode)) {
> case 0:
> nr_pages = hpage_nr_pages(page);
> @@ -1347,6 +1354,15 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> }
> }
>
> + /*
> + * Splice any skipped pages to the start of the LRU list. Note that
> + * this disrupts the LRU order when reclaiming for lower zones but
> + * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
> + * scanning would soon rescan the same pages to skip and put the
> + * system at risk of premature OOM.
> + */
> + if (!list_empty(&pages_skipped))
> + list_splice(&pages_skipped, src);
> *nr_scanned = scan;
> trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan,
> nr_taken, mode, is_file_lru(lru));
Can we avoid splicing pages by skipping pages with scan not incremented?
Hillf
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