[PATCH] mm: memcg: update memcg OOM messages on cgroup2

[Tejun Heo <tj@kernel.org>]

mem_cgroup_print_oom_info() currently prints the same info for cgroup1
and cgroup2 OOMs.  It doesn't make much sense on cgroup2, which
doesn't use memsw or separate kmem accounting - the information
reported is both superflous and insufficient.  This patch updates the
memcg OOM messages on cgroup2 so that

* It prints memory and swap usages and limits used on cgroup2.

* It shows the same information as memory.stat.

I took out the recursive printing for cgroup2 because the amount of
output could be a lot and the benefits aren't clear.

What do you guys think?

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 mm/memcontrol.c |  165 ++++++++++++++++++++++++++++++++------------------------
 1 file changed, 96 insertions(+), 69 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8c0280b3143e..86133e50a0b2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -177,6 +177,7 @@ struct mem_cgroup_event {
 
 static void mem_cgroup_threshold(struct mem_cgroup *memcg);
 static void mem_cgroup_oom_notify(struct mem_cgroup *memcg);
+static void __memory_stat_show(struct seq_file *m, struct mem_cgroup *memcg);
 
 /* Stuffs for move charges at task migration. */
 /*
@@ -1146,33 +1147,49 @@ void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
 
 	rcu_read_unlock();
 
-	pr_info("memory: usage %llukB, limit %llukB, failcnt %lu\n",
-		K((u64)page_counter_read(&memcg->memory)),
-		K((u64)memcg->memory.max), memcg->memory.failcnt);
-	pr_info("memory+swap: usage %llukB, limit %llukB, failcnt %lu\n",
-		K((u64)page_counter_read(&memcg->memsw)),
-		K((u64)memcg->memsw.max), memcg->memsw.failcnt);
-	pr_info("kmem: usage %llukB, limit %llukB, failcnt %lu\n",
-		K((u64)page_counter_read(&memcg->kmem)),
-		K((u64)memcg->kmem.max), memcg->kmem.failcnt);
+	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
+		pr_info("memory: usage %llukB, limit %llukB, failcnt %lu\n",
+			K((u64)page_counter_read(&memcg->memory)),
+			K((u64)memcg->memory.max), memcg->memory.failcnt);
+		pr_info("memory+swap: usage %llukB, limit %llukB, failcnt %lu\n",
+			K((u64)page_counter_read(&memcg->memsw)),
+			K((u64)memcg->memsw.max), memcg->memsw.failcnt);
+		pr_info("kmem: usage %llukB, limit %llukB, failcnt %lu\n",
+			K((u64)page_counter_read(&memcg->kmem)),
+			K((u64)memcg->kmem.max), memcg->kmem.failcnt);
 
-	for_each_mem_cgroup_tree(iter, memcg) {
-		pr_info("Memory cgroup stats for ");
-		pr_cont_cgroup_path(iter->css.cgroup);
-		pr_cont(":");
+		for_each_mem_cgroup_tree(iter, memcg) {
+			pr_info("Memory cgroup stats for ");
+			pr_cont_cgroup_path(iter->css.cgroup);
+			pr_cont(":");
+
+			for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) {
+				if (memcg1_stats[i] == MEMCG_SWAP && !do_swap_account)
+					continue;
+				pr_cont(" %s:%luKB", memcg1_stat_names[i],
+					K(memcg_page_state(iter, memcg1_stats[i])));
+			}
 
-		for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) {
-			if (memcg1_stats[i] == MEMCG_SWAP && !do_swap_account)
-				continue;
-			pr_cont(" %s:%luKB", memcg1_stat_names[i],
-				K(memcg_page_state(iter, memcg1_stats[i])));
+			for (i = 0; i < NR_LRU_LISTS; i++)
+				pr_cont(" %s:%luKB", mem_cgroup_lru_names[i],
+					K(mem_cgroup_nr_lru_pages(iter, BIT(i))));
+
+			pr_cont("\n");
 		}
+	} else {
+		pr_info("memory %llu (max %llu)\n",
+			(u64)page_counter_read(&memcg->memory) * PAGE_SIZE,
+			(u64)memcg->memory.max * PAGE_SIZE);
 
-		for (i = 0; i < NR_LRU_LISTS; i++)
-			pr_cont(" %s:%luKB", mem_cgroup_lru_names[i],
-				K(mem_cgroup_nr_lru_pages(iter, BIT(i))));
+		if (memcg->swap.max == PAGE_COUNTER_MAX)
+			pr_info("swap %llu\n",
+				(u64)page_counter_read(&memcg->swap) * PAGE_SIZE);
+		else
+			pr_info("swap %llu (max %llu)\n",
+				(u64)page_counter_read(&memcg->swap) * PAGE_SIZE,
+				(u64)memcg->swap.max * PAGE_SIZE);
 
-		pr_cont("\n");
+		__memory_stat_show(NULL, memcg);
 	}
 }
 
@@ -5246,9 +5263,15 @@ static int memory_events_show(struct seq_file *m, void *v)
 	return 0;
 }
 
-static int memory_stat_show(struct seq_file *m, void *v)
+#define seq_pr_info(m, fmt, ...) do {					\
+	if ((m))							\
+		seq_printf(m, fmt, ##__VA_ARGS__);			\
+	else								\
+		printk(KERN_INFO fmt, ##__VA_ARGS__);			\
+} while (0)
+
+static void __memory_stat_show(struct seq_file *m, struct mem_cgroup *memcg)
 {
-	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
 	unsigned long stat[MEMCG_NR_STAT];
 	unsigned long events[NR_VM_EVENT_ITEMS];
 	int i;
@@ -5267,26 +5290,26 @@ static int memory_stat_show(struct seq_file *m, void *v)
 	tree_stat(memcg, stat);
 	tree_events(memcg, events);
 
-	seq_printf(m, "anon %llu\n",
-		   (u64)stat[MEMCG_RSS] * PAGE_SIZE);
-	seq_printf(m, "file %llu\n",
-		   (u64)stat[MEMCG_CACHE] * PAGE_SIZE);
-	seq_printf(m, "kernel_stack %llu\n",
-		   (u64)stat[MEMCG_KERNEL_STACK_KB] * 1024);
-	seq_printf(m, "slab %llu\n",
-		   (u64)(stat[NR_SLAB_RECLAIMABLE] +
-			 stat[NR_SLAB_UNRECLAIMABLE]) * PAGE_SIZE);
-	seq_printf(m, "sock %llu\n",
-		   (u64)stat[MEMCG_SOCK] * PAGE_SIZE);
-
-	seq_printf(m, "shmem %llu\n",
-		   (u64)stat[NR_SHMEM] * PAGE_SIZE);
-	seq_printf(m, "file_mapped %llu\n",
-		   (u64)stat[NR_FILE_MAPPED] * PAGE_SIZE);
-	seq_printf(m, "file_dirty %llu\n",
-		   (u64)stat[NR_FILE_DIRTY] * PAGE_SIZE);
-	seq_printf(m, "file_writeback %llu\n",
-		   (u64)stat[NR_WRITEBACK] * PAGE_SIZE);
+	seq_pr_info(m, "anon %llu\n",
+		    (u64)stat[MEMCG_RSS] * PAGE_SIZE);
+	seq_pr_info(m, "file %llu\n",
+		    (u64)stat[MEMCG_CACHE] * PAGE_SIZE);
+	seq_pr_info(m, "kernel_stack %llu\n",
+		    (u64)stat[MEMCG_KERNEL_STACK_KB] * 1024);
+	seq_pr_info(m, "slab %llu\n",
+		    (u64)(stat[NR_SLAB_RECLAIMABLE] +
+			  stat[NR_SLAB_UNRECLAIMABLE]) * PAGE_SIZE);
+	seq_pr_info(m, "sock %llu\n",
+		    (u64)stat[MEMCG_SOCK] * PAGE_SIZE);
+
+	seq_pr_info(m, "shmem %llu\n",
+		    (u64)stat[NR_SHMEM] * PAGE_SIZE);
+	seq_pr_info(m, "file_mapped %llu\n",
+		    (u64)stat[NR_FILE_MAPPED] * PAGE_SIZE);
+	seq_pr_info(m, "file_dirty %llu\n",
+		    (u64)stat[NR_FILE_DIRTY] * PAGE_SIZE);
+	seq_pr_info(m, "file_writeback %llu\n",
+		    (u64)stat[NR_WRITEBACK] * PAGE_SIZE);
 
 	for (i = 0; i < NR_LRU_LISTS; i++) {
 		struct mem_cgroup *mi;
@@ -5294,37 +5317,41 @@ static int memory_stat_show(struct seq_file *m, void *v)
 
 		for_each_mem_cgroup_tree(mi, memcg)
 			val += mem_cgroup_nr_lru_pages(mi, BIT(i));
-		seq_printf(m, "%s %llu\n",
-			   mem_cgroup_lru_names[i], (u64)val * PAGE_SIZE);
+		seq_pr_info(m, "%s %llu\n",
+			    mem_cgroup_lru_names[i], (u64)val * PAGE_SIZE);
 	}
 
-	seq_printf(m, "slab_reclaimable %llu\n",
-		   (u64)stat[NR_SLAB_RECLAIMABLE] * PAGE_SIZE);
-	seq_printf(m, "slab_unreclaimable %llu\n",
-		   (u64)stat[NR_SLAB_UNRECLAIMABLE] * PAGE_SIZE);
+	seq_pr_info(m, "slab_reclaimable %llu\n",
+		    (u64)stat[NR_SLAB_RECLAIMABLE] * PAGE_SIZE);
+	seq_pr_info(m, "slab_unreclaimable %llu\n",
+		    (u64)stat[NR_SLAB_UNRECLAIMABLE] * PAGE_SIZE);
 
 	/* Accumulated memory events */
 
-	seq_printf(m, "pgfault %lu\n", events[PGFAULT]);
-	seq_printf(m, "pgmajfault %lu\n", events[PGMAJFAULT]);
-
-	seq_printf(m, "pgrefill %lu\n", events[PGREFILL]);
-	seq_printf(m, "pgscan %lu\n", events[PGSCAN_KSWAPD] +
-		   events[PGSCAN_DIRECT]);
-	seq_printf(m, "pgsteal %lu\n", events[PGSTEAL_KSWAPD] +
-		   events[PGSTEAL_DIRECT]);
-	seq_printf(m, "pgactivate %lu\n", events[PGACTIVATE]);
-	seq_printf(m, "pgdeactivate %lu\n", events[PGDEACTIVATE]);
-	seq_printf(m, "pglazyfree %lu\n", events[PGLAZYFREE]);
-	seq_printf(m, "pglazyfreed %lu\n", events[PGLAZYFREED]);
-
-	seq_printf(m, "workingset_refault %lu\n",
-		   stat[WORKINGSET_REFAULT]);
-	seq_printf(m, "workingset_activate %lu\n",
-		   stat[WORKINGSET_ACTIVATE]);
-	seq_printf(m, "workingset_nodereclaim %lu\n",
-		   stat[WORKINGSET_NODERECLAIM]);
+	seq_pr_info(m, "pgfault %lu\n", events[PGFAULT]);
+	seq_pr_info(m, "pgmajfault %lu\n", events[PGMAJFAULT]);
+
+	seq_pr_info(m, "pgrefill %lu\n", events[PGREFILL]);
+	seq_pr_info(m, "pgscan %lu\n", events[PGSCAN_KSWAPD] +
+		    events[PGSCAN_DIRECT]);
+	seq_pr_info(m, "pgsteal %lu\n", events[PGSTEAL_KSWAPD] +
+		    events[PGSTEAL_DIRECT]);
+	seq_pr_info(m, "pgactivate %lu\n", events[PGACTIVATE]);
+	seq_pr_info(m, "pgdeactivate %lu\n", events[PGDEACTIVATE]);
+	seq_pr_info(m, "pglazyfree %lu\n", events[PGLAZYFREE]);
+	seq_pr_info(m, "pglazyfreed %lu\n", events[PGLAZYFREED]);
 
+	seq_pr_info(m, "workingset_refault %lu\n",
+		    stat[WORKINGSET_REFAULT]);
+	seq_pr_info(m, "workingset_activate %lu\n",
+		    stat[WORKINGSET_ACTIVATE]);
+	seq_pr_info(m, "workingset_nodereclaim %lu\n",
+		    stat[WORKINGSET_NODERECLAIM]);
+}
+
+static int memory_stat_show(struct seq_file *m, void *v)
+{
+	__memory_stat_show(m, mem_cgroup_from_css(seq_css(m)));
 	return 0;
 }