Andrea,
On Thu, Apr 08, 2010 at 03:51:39AM +0200, Andrea Arcangeli wrote:
> +static unsigned long isolate_migratepages(struct zone *zone,
> + struct compact_control *cc)
> +{
> + unsigned long low_pfn, end_pfn;
> + struct list_head *migratelist = &cc->migratepages;
> +
> + /* Do not scan outside zone boundaries */
> + low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
> +
> + /* Only scan within a pageblock boundary */
> + end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
> +
> + /* Do not cross the free scanner or scan within a memory hole */
> + if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
> + cc->migrate_pfn = end_pfn;
> + return 0;
> + }
> +
> + /*
> + * Ensure that there are not too many pages isolated from the LRU
> + * list by either parallel reclaimers or compaction. If there are,
> + * delay for some time until fewer pages are isolated
> + */
> + while (unlikely(too_many_isolated(zone))) {
> + congestion_wait(BLK_RW_ASYNC, HZ/10);
> +
> + if (fatal_signal_pending(current))
> + return 0;
> + }
> +
> + /* Time to isolate some pages for migration */
> + spin_lock_irq(&zone->lru_lock);
> + for (; low_pfn < end_pfn; low_pfn++) {
> + struct page *page;
> + if (!pfn_valid_within(low_pfn))
> + continue;
> +
> + /* Get the page and skip if free */
> + page = pfn_to_page(low_pfn);
> + if (PageBuddy(page)) {
Should this be
if (PageBuddy(page) || PageTransHuge(page)) {
> + low_pfn += (1 << page_order(page)) - 1;
> + continue;
> + }
instead?
> +
> + /* Try isolate the page */
> + if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0)
> + continue;
> +
> + /* Successfully isolated */
> + del_page_from_lru_list(zone, page, page_lru(page));
> + list_add(&page->lru, migratelist);
> + mem_cgroup_del_lru(page);
> + cc->nr_migratepages++;
> +
> + /* Avoid isolating too much */
> + if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
> + break;
> + }
> +
> + acct_isolated(zone, cc);
> +
> + spin_unlock_irq(&zone->lru_lock);
> + cc->migrate_pfn = low_pfn;
> +
> + return cc->nr_migratepages;
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