[PATCH] VM: add page_state info to per-node meminfo

Add page_state info to the per-node meminfo file in sysfs. This is mostly
just for informational purposes.

The lack of this information was brought up recently during a discussion
regarding pagecache clearing, and I put this patch together to test out one
of the suggestions.

It seems like interesting info to have, so I'm submitting the patch.

Signed-off-by: Martin Hicks <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/base/node.c

···
 	int n;
 	int nid = dev->id;
 	struct sysinfo i;
+	struct page_state ps;
 	unsigned long inactive;
 	unsigned long active;
 	unsigned long free;
 
 	si_meminfo_node(&i, nid);
+	get_page_state_node(&ps, nid);
 	__get_zone_counts(&active, &inactive, &free, NODE_DATA(nid));
+
+	/* Check for negative values in these approximate counters */
+	if ((long)ps.nr_dirty < 0)
+		ps.nr_dirty = 0;
+	if ((long)ps.nr_writeback < 0)
+		ps.nr_writeback = 0;
+	if ((long)ps.nr_mapped < 0)
+		ps.nr_mapped = 0;
+	if ((long)ps.nr_slab < 0)
+		ps.nr_slab = 0;
 
 	n = sprintf(buf, "\n"
 		       "Node %d MemTotal:     %8lu kB\n"
···
 		       "Node %d HighTotal:    %8lu kB\n"
 		       "Node %d HighFree:     %8lu kB\n"
 		       "Node %d LowTotal:     %8lu kB\n"
-		       "Node %d LowFree:      %8lu kB\n",
+		       "Node %d LowFree:      %8lu kB\n"
+		       "Node %d Dirty:        %8lu kB\n"
+		       "Node %d Writeback:    %8lu kB\n"
+		       "Node %d Mapped:       %8lu kB\n"
+		       "Node %d Slab:         %8lu kB\n",
 		       nid, K(i.totalram),
 		       nid, K(i.freeram),
 		       nid, K(i.totalram - i.freeram),
···
 		       nid, K(i.totalhigh),
 		       nid, K(i.freehigh),
 		       nid, K(i.totalram - i.totalhigh),
-		       nid, K(i.freeram - i.freehigh));
+		       nid, K(i.freeram - i.freehigh),
+		       nid, K(ps.nr_dirty),
+		       nid, K(ps.nr_writeback),
+		       nid, K(ps.nr_mapped),
+		       nid, K(ps.nr_slab));
 	n += hugetlb_report_node_meminfo(nid, buf + n);
 	return n;
 }

include/linux/page-flags.h

···
 };
 
 extern void get_page_state(struct page_state *ret);
+extern void get_page_state_node(struct page_state *ret, int node);
 extern void get_full_page_state(struct page_state *ret);
 extern unsigned long __read_page_state(unsigned long offset);
 extern void __mod_page_state(unsigned long offset, unsigned long delta);

mm/page_alloc.c

···
 DEFINE_PER_CPU(long, nr_pagecache_local) = 0;
 #endif
 
-void __get_page_state(struct page_state *ret, int nr)
+void __get_page_state(struct page_state *ret, int nr, cpumask_t *cpumask)
 {
 	int cpu = 0;
 
 	memset(ret, 0, sizeof(*ret));
+	cpus_and(*cpumask, *cpumask, cpu_online_map);
 
-	cpu = first_cpu(cpu_online_map);
+	cpu = first_cpu(*cpumask);
 	while (cpu < NR_CPUS) {
 		unsigned long *in, *out, off;
 
 		in = (unsigned long *)&per_cpu(page_states, cpu);
 
-		cpu = next_cpu(cpu, cpu_online_map);
+		cpu = next_cpu(cpu, *cpumask);
 
 		if (cpu < NR_CPUS)
 			prefetch(&per_cpu(page_states, cpu));
···
 	}
 }
 
-void get_page_state(struct page_state *ret)
+void get_page_state_node(struct page_state *ret, int node)
 {
 	int nr;
+	cpumask_t mask = node_to_cpumask(node);
 
 	nr = offsetof(struct page_state, GET_PAGE_STATE_LAST);
 	nr /= sizeof(unsigned long);
 
-	__get_page_state(ret, nr + 1);
+	__get_page_state(ret, nr+1, &mask);
+}
+
+void get_page_state(struct page_state *ret)
+{
+	int nr;
+	cpumask_t mask = CPU_MASK_ALL;
+
+	nr = offsetof(struct page_state, GET_PAGE_STATE_LAST);
+	nr /= sizeof(unsigned long);
+
+	__get_page_state(ret, nr + 1, &mask);
 }
 
 void get_full_page_state(struct page_state *ret)
 {
-	__get_page_state(ret, sizeof(*ret) / sizeof(unsigned long));
+	cpumask_t mask = CPU_MASK_ALL;
+
+	__get_page_state(ret, sizeof(*ret) / sizeof(unsigned long), &mask);
 }
 
 unsigned long __read_page_state(unsigned long offset)