Re: [PATCH 61 of 66] use compaction for GFP_ATOMIC order > 0

Mel Gorman
2010-11-18T16:31:42Z

On Wed, Nov 03, 2010 at 04:28:36PM +0100, Andrea Arcangeli wrote:
> From: Andrea Arcangeli <aarcange@redhat.com>
>
> This takes advantage of memory compaction to properly generate pages of order >
> 0 if regular page reclaim fails and priority level becomes more severe and we
> don't reach the proper watermarks.
>

I don't think this is related to THP although I see what you're doing.
It should be handled on its own. I'd also wonder if some of the tg3
failures are due to MIGRATE_RESERVE not being set properly when
min_free_kbytes is automatically resized.

> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> ---
>
> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -11,6 +11,9 @@
> /* The full zone was compacted */
> #define COMPACT_COMPLETE 3
>
> +#define COMPACT_MODE_DIRECT_RECLAIM 0
> +#define COMPACT_MODE_KSWAPD 1
> +
> #ifdef CONFIG_COMPACTION
> extern int sysctl_compact_memory;
> extern int sysctl_compaction_handler(struct ctl_table *table, int write,
> @@ -20,6 +23,9 @@ extern int sysctl_extfrag_handler(struct
> void __user *buffer, size_t *length, loff_t *ppos);
>
> extern int fragmentation_index(struct zone *zone, unsigned int order);
> +extern unsigned long compact_zone_order(struct zone *zone,
> + int order, gfp_t gfp_mask,
> + int compact_mode);
> extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
> int order, gfp_t gfp_mask, nodemask_t *mask);
>
> @@ -59,6 +65,13 @@ static inline unsigned long try_to_compa
> return COMPACT_CONTINUE;
> }
>
> +static inline unsigned long compact_zone_order(struct zone *zone,
> + int order, gfp_t gfp_mask,
> + int compact_mode)
> +{
> + return COMPACT_CONTINUE;
> +}
> +
> static inline void defer_compaction(struct zone *zone)
> {
> }
> diff --git a/mm/compaction.c b/mm/compaction.c
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -38,6 +38,8 @@ struct compact_control {
> unsigned int order; /* order a direct compactor needs */
> int migratetype; /* MOVABLE, RECLAIMABLE etc */
> struct zone *zone;
> +
> + int compact_mode;
> };
>
> static unsigned long release_freepages(struct list_head *freelist)
> @@ -357,10 +359,10 @@ static void update_nr_listpages(struct c
> }
>
> static int compact_finished(struct zone *zone,
> - struct compact_control *cc)
> + struct compact_control *cc)
> {
> unsigned int order;
> - unsigned long watermark = low_wmark_pages(zone) + (1 << cc->order);
> + unsigned long watermark;
>
> if (fatal_signal_pending(current))
> return COMPACT_PARTIAL;
> @@ -370,12 +372,27 @@ static int compact_finished(struct zone
> return COMPACT_COMPLETE;
>
> /* Compaction run is not finished if the watermark is not met */
> + if (cc->compact_mode != COMPACT_MODE_KSWAPD)
> + watermark = low_wmark_pages(zone);
> + else
> + watermark = high_wmark_pages(zone);
> + watermark += (1 << cc->order);
> +
> if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
> return COMPACT_CONTINUE;
>
> if (cc->order == -1)
> return COMPACT_CONTINUE;
>
> + /*
> + * Generating only one page of the right order is not enough
> + * for kswapd, we must continue until we're above the high
> + * watermark as a pool for high order GFP_ATOMIC allocations
> + * too.
> + */
> + if (cc->compact_mode == COMPACT_MODE_KSWAPD)
> + return COMPACT_CONTINUE;
> +
> /* Direct compactor: Is a suitable page free? */
> for (order = cc->order; order < MAX_ORDER; order++) {
> /* Job done if page is free of the right migratetype */
> @@ -433,8 +450,9 @@ static int compact_zone(struct zone *zon
> return ret;
> }
>
> -static unsigned long compact_zone_order(struct zone *zone,
> - int order, gfp_t gfp_mask)
> +unsigned long compact_zone_order(struct zone *zone,
> + int order, gfp_t gfp_mask,
> + int compact_mode)
> {
> struct compact_control cc = {
> .nr_freepages = 0,
> @@ -442,6 +460,7 @@ static unsigned long compact_zone_order(
> .order = order,
> .migratetype = allocflags_to_migratetype(gfp_mask),
> .zone = zone,
> + .compact_mode = compact_mode,
> };
> INIT_LIST_HEAD(&cc.freepages);
> INIT_LIST_HEAD(&cc.migratepages);
> @@ -476,7 +495,7 @@ unsigned long try_to_compact_pages(struc
> * made because an assumption is made that the page allocator can satisfy
> * the "cheaper" orders without taking special steps
> */
> - if (order <= PAGE_ALLOC_COSTLY_ORDER || !may_enter_fs || !may_perform_io)
> + if (!order || !may_enter_fs || !may_perform_io)
> return rc;
>
> count_vm_event(COMPACTSTALL);
> @@ -517,7 +536,8 @@ unsigned long try_to_compact_pages(struc
> break;
> }
>
> - status = compact_zone_order(zone, order, gfp_mask);
> + status = compact_zone_order(zone, order, gfp_mask,
> + COMPACT_MODE_DIRECT_RECLAIM);
> rc = max(status, rc);
>
> if (zone_watermark_ok(zone, order, watermark, 0, 0))
> @@ -547,6 +567,7 @@ static int compact_node(int nid)
> .nr_freepages = 0,
> .nr_migratepages = 0,
> .order = -1,
> + .compact_mode = COMPACT_MODE_DIRECT_RECLAIM,
> };
>
> zone = &pgdat->node_zones[zoneid];
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -40,6 +40,7 @@
> #include <linux/memcontrol.h>
> #include <linux/delayacct.h>
> #include <linux/sysctl.h>
> +#include <linux/compaction.h>
>
> #include <asm/tlbflush.h>
> #include <asm/div64.h>
> @@ -2254,6 +2255,7 @@ loop_again:
> * cause too much scanning of the lower zones.
> */
> for (i = 0; i <= end_zone; i++) {
> + int compaction;
> struct zone *zone = pgdat->node_zones + i;
> int nr_slab;
>
> @@ -2283,9 +2285,26 @@ loop_again:
> lru_pages);
> sc.nr_reclaimed += reclaim_state->reclaimed_slab;
> total_scanned += sc.nr_scanned;
> +
> + compaction = 0;
> + if (order &&
> + zone_watermark_ok(zone, 0,
> + high_wmark_pages(zone),
> + end_zone, 0) &&
> + !zone_watermark_ok(zone, order,
> + high_wmark_pages(zone),
> + end_zone, 0)) {
> + compact_zone_order(zone,
> + order,
> + sc.gfp_mask,
> + COMPACT_MODE_KSWAPD);
> + compaction = 1;
> + }
> +
> if (zone->all_unreclaimable)
> continue;
> - if (nr_slab == 0 && !zone_reclaimable(zone))
> + if (!compaction && nr_slab == 0 &&
> + !zone_reclaimable(zone))
> zone->all_unreclaimable = 1;
> /*
> * If we've done a decent amount of scanning and
>

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab