[PATCH 01/11] mm: page_alloc: handle MIGRATE_ISOLATE in free_pcppages_bulk()

Michal Nazarewicz
2011-12-12T14:23:02Z

> On Fri, Nov 18, 2011 at 05:43:08PM +0100, Marek Szyprowski wrote:
>> From: Michal Nazarewicz <mina86@mina86.com>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 9dd443d..58d1a2e 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -628,6 +628,18 @@ static void free_pcppages_bulk(struct zone *zone, int count,
>> page = list_entry(list->prev, struct page, lru);
>> /* must delete as __free_one_page list manipulates */
>> list_del(&page->lru);
>> +
>> + /*
>> + * When page is isolated in set_migratetype_isolate()
>> + * function it's page_private is not changed since the
>> + * function has no way of knowing if it can touch it.
>> + * This means that when a page is on PCP list, it's
>> + * page_private no longer matches the desired migrate
>> + * type.
>> + */
>> + if (get_pageblock_migratetype(page) == MIGRATE_ISOLATE)
>> + set_page_private(page, MIGRATE_ISOLATE);
>> +

On Mon, 12 Dec 2011 14:42:35 +0100, Mel Gorman <mel@csn.ul.ie> wrote:
> How much of a problem is this in practice?

IIRC, this lead to allocation being made from area marked as isolated
or some such.

> [...] I'd go as far to say that it would be preferable to drain the
> per-CPU lists after you set pageblocks MIGRATE_ISOLATE. The IPIs also have
> overhead but it will be incurred for the rare rather than the common case.

I'll look into that.

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