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SubjectRe: [RFC 8/8] compaction: make compaction use in-order putback
On Wed, 27 Apr 2011 01:25:25 +0900
Minchan Kim <minchan.kim@gmail.com> wrote:

> Compaction is good solution to get contiguos page but it makes
> LRU churing which is not good.
> This patch makes that compaction code use in-order putback so
> after compaction completion, migrated pages are keeping LRU ordering.
>
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
> ---
> mm/compaction.c | 22 +++++++++++++++-------
> 1 files changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index a2f6e96..480d2ac 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -211,11 +211,11 @@ static void isolate_freepages(struct zone *zone,
> /* Update the number of anon and file isolated pages in the zone */
> static void acct_isolated(struct zone *zone, struct compact_control *cc)
> {
> - struct page *page;
> + struct pages_lru *pages_lru;
> unsigned int count[NR_LRU_LISTS] = { 0, };
>
> - list_for_each_entry(page, &cc->migratepages, lru) {
> - int lru = page_lru_base_type(page);
> + list_for_each_entry(pages_lru, &cc->migratepages, lru) {
> + int lru = page_lru_base_type(pages_lru->page);
> count[lru]++;
> }
>
> @@ -281,6 +281,7 @@ static unsigned long isolate_migratepages(struct zone *zone,
> spin_lock_irq(&zone->lru_lock);
> for (; low_pfn < end_pfn; low_pfn++) {
> struct page *page;
> + struct pages_lru *pages_lru;
> bool locked = true;
>
> /* give a chance to irqs before checking need_resched() */
> @@ -334,10 +335,16 @@ static unsigned long isolate_migratepages(struct zone *zone,
> continue;
> }
>
> + pages_lru = kmalloc(sizeof(struct pages_lru), GFP_ATOMIC);
> + if (pages_lru)
> + continue;

Hmm, can't we use fixed size of statically allocated pages_lru, per-node or
per-zone ? I think using kmalloc() in memory reclaim path is risky.

Thanks,
-Kame



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