mm: kswapd: use the classzone idx that kswapd was using for sleeping_prematurely()
When kswapd is woken up for a high-order allocation, it takes account of the highest usable zone by the caller (the classzone idx). During allocation, this index is used to select the lowmem_reserve[] that should be applied to the watermark calculation in zone_watermark_ok(). When balancing a node, kswapd considers the highest unbalanced zone to be the classzone index. This will always be at least be the callers classzone_idx and can be higher. However, sleeping_prematurely() always considers the lowest zone (e.g. ZONE_DMA) to be the classzone index. This means that sleeping_prematurely() can consider a zone to be balanced that is unusable by the allocation request that originally woke kswapd. This patch changes sleeping_prematurely() to use a classzone_idx matching the value it used in balance_pgdat(). Signed-off-by: Mel Gorman <mel@csn.ul.ie> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Reviewed-by: Eric B Munson <emunson@mgebm.net> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Simon Kirby <sim@hostway.ca> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Shaohua Li <shaohua.li@intel.com> Cc: Dave Hansen <dave@linux.vnet.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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mm/vmscan.c
29
mm/vmscan.c
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@ -2227,7 +2227,8 @@ static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
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}
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/* is kswapd sleeping prematurely? */
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static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
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static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
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int classzone_idx)
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{
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int i;
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unsigned long balanced = 0;
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@ -2235,7 +2236,7 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
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/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
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if (remaining)
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return 1;
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return true;
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/* Check the watermark levels */
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for (i = 0; i < pgdat->nr_zones; i++) {
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@ -2256,7 +2257,7 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
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}
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if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
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0, 0))
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classzone_idx, 0))
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all_zones_ok = false;
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else
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balanced += zone->present_pages;
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@ -2268,7 +2269,7 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
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* must be balanced
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*/
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if (order)
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return pgdat_balanced(pgdat, balanced, 0);
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return pgdat_balanced(pgdat, balanced, classzone_idx);
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else
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return !all_zones_ok;
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}
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@ -2295,7 +2296,7 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
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* of pages is balanced across the zones.
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*/
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static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
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int classzone_idx)
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int *classzone_idx)
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{
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int all_zones_ok;
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unsigned long balanced;
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@ -2358,6 +2359,7 @@ loop_again:
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if (!zone_watermark_ok_safe(zone, order,
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high_wmark_pages(zone), 0, 0)) {
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end_zone = i;
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*classzone_idx = i;
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break;
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}
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}
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@ -2451,12 +2453,12 @@ loop_again:
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* spectulatively avoid congestion waits
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*/
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zone_clear_flag(zone, ZONE_CONGESTED);
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if (i <= classzone_idx)
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if (i <= *classzone_idx)
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balanced += zone->present_pages;
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}
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}
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if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, classzone_idx)))
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if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
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break; /* kswapd: all done */
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/*
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* OK, kswapd is getting into trouble. Take a nap, then take
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@ -2485,7 +2487,7 @@ out:
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* high-order: Balanced zones must make up at least 25% of the node
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* for the node to be balanced
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*/
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if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, classzone_idx)))) {
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if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
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cond_resched();
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try_to_freeze();
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@ -2546,10 +2548,11 @@ out:
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* if another caller entered the allocator slow path while kswapd
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* was awake, order will remain at the higher level
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*/
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*classzone_idx = end_zone;
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return order;
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}
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static void kswapd_try_to_sleep(pg_data_t *pgdat, int order)
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static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
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{
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long remaining = 0;
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DEFINE_WAIT(wait);
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@ -2560,7 +2563,7 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int order)
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prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
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/* Try to sleep for a short interval */
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if (!sleeping_prematurely(pgdat, order, remaining)) {
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if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
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remaining = schedule_timeout(HZ/10);
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finish_wait(&pgdat->kswapd_wait, &wait);
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prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
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@ -2570,7 +2573,7 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int order)
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* After a short sleep, check if it was a premature sleep. If not, then
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* go fully to sleep until explicitly woken up.
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*/
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if (!sleeping_prematurely(pgdat, order, remaining)) {
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if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
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trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
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/*
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@ -2658,7 +2661,7 @@ static int kswapd(void *p)
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order = new_order;
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classzone_idx = new_classzone_idx;
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} else {
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kswapd_try_to_sleep(pgdat, order);
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kswapd_try_to_sleep(pgdat, order, classzone_idx);
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order = pgdat->kswapd_max_order;
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classzone_idx = pgdat->classzone_idx;
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pgdat->kswapd_max_order = 0;
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@ -2675,7 +2678,7 @@ static int kswapd(void *p)
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*/
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if (!ret) {
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trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
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order = balance_pgdat(pgdat, order, classzone_idx);
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order = balance_pgdat(pgdat, order, &classzone_idx);
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}
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}
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return 0;
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