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Message-ID: <20160831084942.GX8119@techsingularity.net>
Date: Wed, 31 Aug 2016 09:49:42 +0100
From: Mel Gorman <mgorman@...hsingularity.net>
To: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
Vlastimil Babka <vbabka@...e.cz>,
Johannes Weiner <hannes@...xchg.org>,
Minchan Kim <minchan@...nel.org>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
LKML <linux-kernel@...r.kernel.org>,
Michael Ellerman <mpe@...erman.id.au>,
linuxppc-dev@...ts.ozlabs.org,
Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
Hari Bathini <hbathini@...ux.vnet.ibm.com>
Subject: Re: [PATCH 07/34] mm, vmscan: make kswapd reclaim in terms of nodes
On Wed, Aug 31, 2016 at 11:39:59AM +0530, Srikar Dronamraju wrote:
> This indeed fixes the problem.
> Please add my
> Tested-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
>
Ok, thanks. Unfortunately we cannot do a wide conversion like this
because some users of populated_zone() really meant to check for
present_pages. In all cases, the expectation was that reserved pages
would be tiny but fadump messes that up. Can you verify this also works
please?
---8<---
mm, vmscan: Only allocate and reclaim from zones with pages managed by the buddy allocator
Firmware Assisted Dump (FA_DUMP) on ppc64 reserves substantial amounts
of memory when booting a secondary kernel. Srikar Dronamraju reported that
multiple nodes may have no memory managed by the buddy allocator but still
return true for populated_zone().
Commit 1d82de618ddd ("mm, vmscan: make kswapd reclaim in terms of nodes")
was reported to cause kswapd to spin at 100% CPU usage when fadump was
enabled. The old code happened to deal with the situation of a populated
node with zero free pages by co-incidence but the current code tries to
reclaim populated zones without realising that is impossible.
We cannot just convert populated_zone() as many existing users really
need to check for present_pages. This patch introduces a managed_zone()
helper and uses it in the few cases where it is critical that the check
is made for managed pages -- zonelist constuction and page reclaim.
Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
---
include/linux/mmzone.h | 11 +++++++++--
mm/page_alloc.c | 4 ++--
mm/vmscan.c | 22 +++++++++++-----------
3 files changed, 22 insertions(+), 15 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index d572b78b65e1..69f886b79656 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -828,9 +828,16 @@ unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
*/
#define zone_idx(zone) ((zone) - (zone)->zone_pgdat->node_zones)
-static inline int populated_zone(struct zone *zone)
+/* Returns true if a zone has pages managed by the buddy allocator */
+static inline bool managed_zone(struct zone *zone)
{
- return (!!zone->present_pages);
+ return zone->managed_pages;
+}
+
+/* Returns true if a zone has memory */
+static inline bool populated_zone(struct zone *zone)
+{
+ return zone->present_pages;
}
extern int movable_zone;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1c09d9f7f692..ea7558149ee5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4405,7 +4405,7 @@ static int build_zonelists_node(pg_data_t *pgdat, struct zonelist *zonelist,
do {
zone_type--;
zone = pgdat->node_zones + zone_type;
- if (populated_zone(zone)) {
+ if (managed_zone(zone)) {
zoneref_set_zone(zone,
&zonelist->_zonerefs[nr_zones++]);
check_highest_zone(zone_type);
@@ -4643,7 +4643,7 @@ static void build_zonelists_in_zone_order(pg_data_t *pgdat, int nr_nodes)
for (j = 0; j < nr_nodes; j++) {
node = node_order[j];
z = &NODE_DATA(node)->node_zones[zone_type];
- if (populated_zone(z)) {
+ if (managed_zone(z)) {
zoneref_set_zone(z,
&zonelist->_zonerefs[pos++]);
check_highest_zone(zone_type);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 98774f45b04a..55943a284082 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1665,7 +1665,7 @@ static bool inactive_reclaimable_pages(struct lruvec *lruvec,
for (zid = sc->reclaim_idx; zid >= 0; zid--) {
zone = &pgdat->node_zones[zid];
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
if (zone_page_state_snapshot(zone, NR_ZONE_LRU_BASE +
@@ -2036,7 +2036,7 @@ static bool inactive_list_is_low(struct lruvec *lruvec, bool file,
struct zone *zone = &pgdat->node_zones[zid];
unsigned long inactive_zone, active_zone;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
inactive_zone = zone_page_state(zone,
@@ -2171,7 +2171,7 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
for (z = 0; z < MAX_NR_ZONES; z++) {
struct zone *zone = &pgdat->node_zones[z];
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
total_high_wmark += high_wmark_pages(zone);
@@ -2508,7 +2508,7 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
/* If compaction would go ahead or the allocation would succeed, stop */
for (z = 0; z <= sc->reclaim_idx; z++) {
struct zone *zone = &pgdat->node_zones[z];
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
@@ -2835,7 +2835,7 @@ static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
for (i = 0; i <= ZONE_NORMAL; i++) {
zone = &pgdat->node_zones[i];
- if (!populated_zone(zone) ||
+ if (!managed_zone(zone) ||
pgdat_reclaimable_pages(pgdat) == 0)
continue;
@@ -3136,7 +3136,7 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, int classzone_idx)
for (i = 0; i <= classzone_idx; i++) {
struct zone *zone = pgdat->node_zones + i;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
if (!zone_balanced(zone, order, classzone_idx))
@@ -3164,7 +3164,7 @@ static bool kswapd_shrink_node(pg_data_t *pgdat,
sc->nr_to_reclaim = 0;
for (z = 0; z <= sc->reclaim_idx; z++) {
zone = pgdat->node_zones + z;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX);
@@ -3237,7 +3237,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
if (buffer_heads_over_limit) {
for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
zone = pgdat->node_zones + i;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
sc.reclaim_idx = i;
@@ -3257,7 +3257,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
*/
for (i = classzone_idx; i >= 0; i--) {
zone = pgdat->node_zones + i;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
if (zone_balanced(zone, sc.order, classzone_idx))
@@ -3503,7 +3503,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
pg_data_t *pgdat;
int z;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
return;
if (!cpuset_zone_allowed(zone, GFP_KERNEL | __GFP_HARDWALL))
@@ -3517,7 +3517,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
/* Only wake kswapd if all zones are unbalanced */
for (z = 0; z <= classzone_idx; z++) {
zone = pgdat->node_zones + z;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
if (zone_balanced(zone, order, classzone_idx))
--
Mel Gorman
SUSE Labs
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