[Devel] Re: [PATCH][for -mm] Fix and Enhancements for memory cgroup [4/6] avoid handling !LRU page in mem_cgroup_isolate_pages

[Balbir Singh]

KAMEZAWA Hiroyuki wrote:
> This patch makes mem_cgroup_isolate_pages() to be
> 
>   - ignore !PageLRU pages.
>   - fixes the bug that it makes no progress if page_zone(page) != zone
>     page once find. (just increment scan in this case.)
> 
> kswapd and memory migraion removes a page from list when it handles
> a page for reclaiming/migration. 
> 
> __isolate_lru_page() doesn't moves page !PageLRU pages, then, it will
> be safe to avoid touching the page and its page_cgroup.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
> 
>  mm/memcontrol.c |   13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> Index: devel-2.6.23-rc8-mm2/mm/memcontrol.c
> ===================================================================
> --- devel-2.6.23-rc8-mm2.orig/mm/memcontrol.c
> +++ devel-2.6.23-rc8-mm2/mm/memcontrol.c
> @@ -227,7 +227,7 @@ unsigned long mem_cgroup_isolate_pages(u
>  	unsigned long scan;
>  	LIST_HEAD(pc_list);
>  	struct list_head *src;
> -	struct page_cgroup *pc;
> +	struct page_cgroup *pc, *tmp;
> 
>  	if (active)
>  		src = &mem_cont->active_list;
> @@ -235,11 +235,18 @@ unsigned long mem_cgroup_isolate_pages(u
>  		src = &mem_cont->inactive_list;
> 
>  	spin_lock(&mem_cont->lru_lock);
> -	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
> -		pc = list_entry(src->prev, struct page_cgroup, lru);
> +	scan = 0;
> +	list_for_each_entry_safe_reverse(pc, tmp, src, lru) {
> +		if (scan++ > nr_taken)
> +			break;
>  		page = pc->page;
>  		VM_BUG_ON(!pc);
> 
> +		if (unlikely(!PageLRU(page))) {
> +			scan--;
> +			continue;
> +		}
> +
>  		if (PageActive(page) && !active) {
>  			__mem_cgroup_move_lists(pc, true);
>  			scan--;
> 

Looks good to me

Acked-by: Balbir Singh <balbir at linux.vnet.ibm.com>

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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