Messages in this thread | | | Subject | Re: [PATCH v9] mm: compaction: handle incorrect MIGRATE_UNMOVABLE type pageblocks | Date | Mon, 04 Jun 2012 16:22:51 +0200 | From | "Michal Nazarewicz" <> |
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On Mon, 04 Jun 2012 15:43:56 +0200, Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> wrote: > +/* > + * Returns true if MIGRATE_UNMOVABLE pageblock can be successfully > + * converted to MIGRATE_MOVABLE type, false otherwise. > + */ > +static bool can_rescue_unmovable_pageblock(struct page *page, bool locked) > +{ > + unsigned long pfn, start_pfn, end_pfn; > + struct page *start_page, *end_page, *cursor_page; > + > + pfn = page_to_pfn(page); > + start_pfn = pfn & ~(pageblock_nr_pages - 1); > + end_pfn = start_pfn + pageblock_nr_pages - 1; > + > + start_page = pfn_to_page(start_pfn); > + end_page = pfn_to_page(end_pfn); > + > + for (cursor_page = start_page, pfn = start_pfn; cursor_page <= end_page; > + pfn++, cursor_page++) { > + struct zone *zone = page_zone(start_page); > + unsigned long flags; > + > + if (!pfn_valid_within(pfn)) > + continue; > + > + /* Do not deal with pageblocks that overlap zones */ > + if (page_zone(cursor_page) != zone) > + return false; > + > + if (!locked) > + spin_lock_irqsave(&zone->lock, flags); > + > + if (PageBuddy(cursor_page)) { > + int order = page_order(cursor_page); >-/* Returns true if the page is within a block suitable for migration to */ > -static bool suitable_migration_target(struct page *page) > + pfn += (1 << order) - 1; > + cursor_page += (1 << order) - 1; > + > + if (!locked) > + spin_unlock_irqrestore(&zone->lock, flags); > + continue; > + } else if (page_count(cursor_page) == 0 || > + PageLRU(cursor_page)) { > + if (!locked) > + spin_unlock_irqrestore(&zone->lock, flags); > + continue; > + } > + > + if (!locked) > + spin_unlock_irqrestore(&zone->lock, flags);
spin_unlock in three spaces is ugly. How about adding a flag that holds the result of the function which you use as for loop condition and you set it to false inside an additional else clause? Eg.:
bool result = true; for (...; result && cursor_page <= end_page; ...) { ... if (!pfn_valid_within(pfn)) continue; if (page_zone(cursor_page) != zone) return false; if (!locked) spin_lock_irqsave(...); if (PageBuddy(...)) { ... } else if (page_count(cursor_page) == 0 || PageLRU(cursor_page)) { ... } else { result = false; } if (!locked) spin_unlock_irqsave(...); } return result;
> + return false; > + } > + > + return true; > +}
How do you make sure that a page is not allocated while this runs? Or you just don't care? Not that even with zone lock, page may be allocated from pcp list on (another) CPU.
-- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michał “mina86” Nazarewicz (o o) ooo +----<email/xmpp: mpn@google.com>--------------ooO--(_)--Ooo-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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