linux-ext4 - [PATCH] mm, oom: report compaction/migration stats for higher order requests

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Date:	Sun, 14 Aug 2016 14:53:27 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	arekm@...en.pl
Cc:	linux-ext4@...r.kernel.org, linux-mm@...r.kernel.org
Subject: [PATCH] mm, oom: report compaction/migration stats for higher order
 requests

From: Michal Hocko <mhocko@...e.com>

Both oom and the allocation failure reports are not providing any
information about the compaction/migration counters which might give us
a clue what went wrong and why we are OOM for the particular order -
e.g. the compaction fails constantly because it cannot isolate any pages
or that the migration fails. So far we have been asking for /proc/vmstat
content before and after the OOM which is rather clumsy, especially when
the OOM is not 100% reproducible.

Extend show_mem() to understand a new filter (SHOW_COMPACTION_STATS)
which is enabled only for higer order paths.

Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 include/linux/mm.h |  1 +
 lib/show_mem.c     | 14 ++++++++++++++
 mm/oom_kill.c      |  2 +-
 mm/page_alloc.c    |  2 ++
 4 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7e44613c5078..b4859547acc4 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1146,6 +1146,7 @@ extern void pagefault_out_of_memory(void);
  * various contexts.
  */
 #define SHOW_MEM_FILTER_NODES		(0x0001u)	/* disallowed nodes */
+#define SHOW_COMPACTION_STATS		(0x0002u)
 
 extern void show_free_areas(unsigned int flags);
 extern bool skip_free_areas_node(unsigned int flags, int nid);
diff --git a/lib/show_mem.c b/lib/show_mem.c
index 1feed6a2b12a..595ba00f5836 100644
--- a/lib/show_mem.c
+++ b/lib/show_mem.c
@@ -8,6 +8,7 @@
 #include <linux/mm.h>
 #include <linux/quicklist.h>
 #include <linux/cma.h>
+#include <linux/vm_event_item.h>
 
 void show_mem(unsigned int filter)
 {
@@ -17,6 +18,19 @@ void show_mem(unsigned int filter)
 	printk("Mem-Info:\n");
 	show_free_areas(filter);
 
+#ifdef CONFIG_COMPACTION
+	if (filter & SHOW_COMPACTION_STATS) {
+		printk("compaction_stall:%lu compaction_fail:%lu "
+		       "compact_migrate_scanned:%lu compact_free_scanned:%lu "
+		       "compact_isolated:%lu "
+		       "pgmigrate_success:%lu pgmigrate_fail:%lu\n",
+		       global_page_state(COMPACTSTALL), global_page_state(COMPACTFAIL),
+		       global_page_state(COMPACTMIGRATE_SCANNED), global_page_state(COMPACTFAIL),
+		       global_page_state(COMPACTISOLATED),
+		       global_page_state(PGMIGRATE_SUCCESS), global_page_state(PGMIGRATE_FAIL));
+	}
+#endif
+
 	for_each_online_pgdat(pgdat) {
 		unsigned long flags;
 		int zoneid;
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 463cdd22d4e0..5e7a09f4dbc9 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -419,7 +419,7 @@ static void dump_header(struct oom_control *oc, struct task_struct *p)
 	if (oc->memcg)
 		mem_cgroup_print_oom_info(oc->memcg, p);
 	else
-		show_mem(SHOW_MEM_FILTER_NODES);
+		show_mem(SHOW_MEM_FILTER_NODES | (oc->order)?SHOW_COMPACTION_STATS:0);
 	if (sysctl_oom_dump_tasks)
 		dump_tasks(oc->memcg, oc->nodemask);
 }
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9d46b65061be..adf0cb655827 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2999,6 +2999,8 @@ void warn_alloc_failed(gfp_t gfp_mask, unsigned int order, const char *fmt, ...)
 	pr_warn("%s: page allocation failure: order:%u, mode:%#x(%pGg)\n",
 		current->comm, order, gfp_mask, &gfp_mask);
 	dump_stack();
+	if (order)
+		filter |= SHOW_COMPACTION_STATS;
 	if (!should_suppress_show_mem())
 		show_mem(filter);
 }
-- 
2.8.1

-- 
Michal Hocko
SUSE Labs
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