Re: [PATCH v3] vmscan,memcg: reintroduce sc->may_swap

[Johannes Weiner <hannes@cmpxchg.org>]

On Sun, Apr 19, 2009 at 09:42:14PM +0900, KOSAKI Motohiro wrote:
> 
> next version here :)
> 
> ==================================
> Subject: [PATCH v3] vmscan,memcg: reintroduce sc->may_swap
> 
> vmscan-rename-scmay_swap-to-may_unmap.patch removed may_swap flag,
> but memcg had used it as a flag for "we need to use swap?", as the
> name indicate.
> 
> And in current implementation, memcg cannot reclaim mapped file caches
> when mem+swap hits the limit.
> 
> re-introduce may_swap flag and handle it at get_scan_ratio().
> This patch doesn't influence any scan_control users other than memcg.
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

> --
>  mm/vmscan.c |   12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> Index: b/mm/vmscan.c
> ===================================================================
> --- a/mm/vmscan.c	2009-04-17 21:39:58.000000000 +0900
> +++ b/mm/vmscan.c	2009-04-19 20:33:00.000000000 +0900
> @@ -64,6 +64,9 @@ struct scan_control {
>  	/* Can mapped pages be reclaimed? */
>  	int may_unmap;
>  
> +	/* Can pages be swapped as part of reclaim? */
> +	int may_swap;
> +
>  	/* This context's SWAP_CLUSTER_MAX. If freeing memory for
>  	 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
>  	 * In this context, it doesn't matter that we scan the
> @@ -1387,7 +1390,7 @@ static void get_scan_ratio(struct zone *
>  	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
>  
>  	/* If we have no swap space, do not bother scanning anon pages. */
> -	if (nr_swap_pages <= 0) {
> +	if (!sc->may_swap || (nr_swap_pages <= 0)) {
>  		percent[0] = 0;
>  		percent[1] = 100;
>  		return;
> @@ -1704,6 +1707,7 @@ unsigned long try_to_free_pages(struct z
>  		.may_writepage = !laptop_mode,
>  		.swap_cluster_max = SWAP_CLUSTER_MAX,
>  		.may_unmap = 1,
> +		.may_swap = 1,
>  		.swappiness = vm_swappiness,
>  		.order = order,
>  		.mem_cgroup = NULL,
> @@ -1724,6 +1728,7 @@ unsigned long try_to_free_mem_cgroup_pag
>  	struct scan_control sc = {
>  		.may_writepage = !laptop_mode,
>  		.may_unmap = 1,
> +		.may_swap = !noswap,
>  		.swap_cluster_max = SWAP_CLUSTER_MAX,
>  		.swappiness = swappiness,
>  		.order = 0,
> @@ -1733,9 +1738,6 @@ unsigned long try_to_free_mem_cgroup_pag
>  	};
>  	struct zonelist *zonelist;
>  
> -	if (noswap)
> -		sc.may_unmap = 0;
> -
>  	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
>  			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
>  	zonelist = NODE_DATA(numa_node_id())->node_zonelists;
> @@ -1774,6 +1776,7 @@ static unsigned long balance_pgdat(pg_da
>  	struct scan_control sc = {
>  		.gfp_mask = GFP_KERNEL,
>  		.may_unmap = 1,
> +		.may_swap = 1,
>  		.swap_cluster_max = SWAP_CLUSTER_MAX,
>  		.swappiness = vm_swappiness,
>  		.order = order,
> @@ -2304,6 +2307,7 @@ static int __zone_reclaim(struct zone *z
>  	struct scan_control sc = {
>  		.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
>  		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
> +		.may_swap = 1,
>  		.swap_cluster_max = max_t(unsigned long, nr_pages,
>  					SWAP_CLUSTER_MAX),
>  		.gfp_mask = gfp_mask,
> 
> 
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