Re: [PATCHv2 1/5] vmscan: separate sc.swap_cluster_max andsc.nr_max_reclaim

[Minchan Kim]

Hi, Kosaki.

On Mon, 2 Nov 2009 00:08:44 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> wrote:

> Currently, sc.scap_cluster_max has double meanings.
> 
>  1) reclaim batch size as isolate_lru_pages()'s argument
>  2) reclaim baling out thresolds
> 
> The two meanings pretty unrelated. Thus, Let's separate it.
> this patch doesn't change any behavior.
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> Cc: Rafael J. Wysocki <rjw@xxxxxxx>
> Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
> ---
>  mm/vmscan.c |   21 +++++++++++++++------
>  1 files changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index f805958..6a3eb9f 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -55,6 +55,9 @@ struct scan_control {
>  	/* Number of pages freed so far during a call to shrink_zones() */
>  	unsigned long nr_reclaimed;
>  
> +	/* How many pages shrink_list() should reclaim */
> +	unsigned long nr_to_reclaim;

If you try to divide meaning of swap_cluster_max, 
How about changing 'swap_cluster_max', too?

It has a meaning which represents 'batch size'. ;)
I hope we change it in this chance.

> +
>  	/* This context's GFP mask */
>  	gfp_t gfp_mask;
>  
> @@ -1585,6 +1588,7 @@ static void shrink_zone(int priority, struct zone *zone,
>  	enum lru_list l;
>  	unsigned long nr_reclaimed = sc->nr_reclaimed;
>  	unsigned long swap_cluster_max = sc->swap_cluster_max;
> +	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
>  	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
>  	int noswap = 0;
>  
> @@ -1634,8 +1638,7 @@ static void shrink_zone(int priority, struct zone *zone,
>  		 * with multiple processes reclaiming pages, the total
>  		 * freeing target can get unreasonably large.
>  		 */

How about adding following comment or more good one.
'kswapd doesn't bail out because it has 'MAX' nr_to_reclaim'.

> -		if (nr_reclaimed > swap_cluster_max &&
> -			priority < DEF_PRIORITY && !current_is_kswapd())
> +		if (nr_reclaimed > nr_to_reclaim && priority < DEF_PRIORITY)
>  			break;
>  	}
>  
> @@ -1733,6 +1736,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
>  	struct zoneref *z;
>  	struct zone *zone;
>  	enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
> +	unsigned long writeback_threshold;
>  
>  	delayacct_freepages_start();
>  
> @@ -1768,7 +1772,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
>  			}
>  		}
>  		total_scanned += sc->nr_scanned;
> -		if (sc->nr_reclaimed >= sc->swap_cluster_max) {
> +		if (sc->nr_reclaimed >= sc->nr_to_reclaim) {
>  			ret = sc->nr_reclaimed;
>  			goto out;
>  		}
> @@ -1780,8 +1784,8 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
>  		 * that's undesirable in laptop mode, where we *want* lumpy
>  		 * writeout.  So in laptop mode, write out the whole world.
>  		 */
> -		if (total_scanned > sc->swap_cluster_max +
> -					sc->swap_cluster_max / 2) {
> +		writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
> +		if (total_scanned > writeback_threshold) {
>  			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
>  			sc->may_writepage = 1;
>  		}
> @@ -1827,6 +1831,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
>  		.gfp_mask = gfp_mask,
>  		.may_writepage = !laptop_mode,
>  		.swap_cluster_max = SWAP_CLUSTER_MAX,
> +		.nr_to_reclaim = SWAP_CLUSTER_MAX,
>  		.may_unmap = 1,
>  		.may_swap = 1,
>  		.swappiness = vm_swappiness,
> @@ -1885,6 +1890,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
>  		.may_unmap = 1,
>  		.may_swap = !noswap,
>  		.swap_cluster_max = SWAP_CLUSTER_MAX,
> +		.nr_to_reclaim = SWAP_CLUSTER_MAX,
>  		.swappiness = swappiness,
>  		.order = 0,
>  		.mem_cgroup = mem_cont,
> @@ -1932,6 +1938,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
>  		.may_unmap = 1,
>  		.may_swap = 1,
>  
		.swap_cluster_max = SWAP_CLUSTER_MAX,
Or add comment in here. 

'kswapd doesn't want to be bailed out while reclaim.'

> +		.nr_to_reclaim = ULONG_MAX,
>  		.swappiness = vm_swappiness,
>  		.order = order,
>  		.mem_cgroup = NULL,
> @@ -2549,7 +2556,9 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
>  		.may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
>  		.may_swap = 1,
>  		.swap_cluster_max = max_t(unsigned long, nr_pages,
> -					SWAP_CLUSTER_MAX),
> +				       SWAP_CLUSTER_MAX),
> +		.nr_to_reclaim = max_t(unsigned long, nr_pages,
> +				       SWAP_CLUSTER_MAX),
>  		.gfp_mask = gfp_mask,
>  		.swappiness = vm_swappiness,
>  		.order = order,
> -- 
> 1.6.2.5
> 
> 
> 
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-- 
Kind regards,
Minchan Kim
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