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mm/page_alloc: limit the number of pages on PCP lists when reclaim is active

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When kswapd is active then direct reclaim is potentially active.  In
either case, it is possible that a zone would be balanced if pages were
not trapped on PCP lists.  Instead of draining remote pages, simply limit
the size of the PCP lists while kswapd is active.

Link: https://lkml.kernel.org/r/20210525080119.5455-6-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mel Gorman 2021-06-28 19:42:21 -07:00 committed by Linus Torvalds
parent 3b12e7e979
commit c49c2c47da
3 changed files with 54 additions and 1 deletions
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1
include/linux/mmzone.h
View File

@ -647,6 +647,7 @@ enum zone_flags {
ZONE_BOOSTED_WATERMARK, /* zone recently boosted watermarks.
* Cleared when kswapd is woken.
*/
ZONE_RECLAIM_ACTIVE, /* kswapd may be scanning the zone. */
};
static inline unsigned long zone_managed_pages(struct zone *zone)

19
mm/page_alloc.c
View File

@ -3302,6 +3302,23 @@ static int nr_pcp_free(struct per_cpu_pages *pcp, int high, int batch)
return batch;
}
static int nr_pcp_high(struct per_cpu_pages *pcp, struct zone *zone)
{
int high = READ_ONCE(pcp->high);
if (unlikely(!high))
return 0;
if (!test_bit(ZONE_RECLAIM_ACTIVE, &zone->flags))
return high;
/*
* If reclaim is active, limit the number of pages that can be
* stored on pcp lists
*/
return min(READ_ONCE(pcp->batch) << 2, high);
}
static void free_unref_page_commit(struct page *page, unsigned long pfn,
int migratetype)
{
@ -3313,7 +3330,7 @@ static void free_unref_page_commit(struct page *page, unsigned long pfn,
pcp = this_cpu_ptr(zone->per_cpu_pageset);
list_add(&page->lru, &pcp->lists[migratetype]);
pcp->count++;
high = READ_ONCE(pcp->high);
high = nr_pcp_high(pcp, zone);
if (pcp->count >= high) {
int batch = READ_ONCE(pcp->batch);

35
mm/vmscan.c
View File

@ -3722,6 +3722,38 @@ static bool kswapd_shrink_node(pg_data_t *pgdat,
return sc->nr_scanned >= sc->nr_to_reclaim;
}
/* Page allocator PCP high watermark is lowered if reclaim is active. */
static inline void
update_reclaim_active(pg_data_t *pgdat, int highest_zoneidx, bool active)
{
int i;
struct zone *zone;
for (i = 0; i <= highest_zoneidx; i++) {
zone = pgdat->node_zones + i;
if (!managed_zone(zone))
continue;
if (active)
set_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
else
clear_bit(ZONE_RECLAIM_ACTIVE, &zone->flags);
}
}
static inline void
set_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
{
update_reclaim_active(pgdat, highest_zoneidx, true);
}
static inline void
clear_reclaim_active(pg_data_t *pgdat, int highest_zoneidx)
{
update_reclaim_active(pgdat, highest_zoneidx, false);
}
/*
* For kswapd, balance_pgdat() will reclaim pages across a node from zones
* that are eligible for use by the caller until at least one zone is
@ -3774,6 +3806,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
boosted = nr_boost_reclaim;
restart:
set_reclaim_active(pgdat, highest_zoneidx);
sc.priority = DEF_PRIORITY;
do {
unsigned long nr_reclaimed = sc.nr_reclaimed;
@ -3907,6 +3940,8 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
pgdat->kswapd_failures++;
out:
clear_reclaim_active(pgdat, highest_zoneidx);
/* If reclaim was boosted, account for the reclaim done in this pass */
if (boosted) {
unsigned long flags;