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-rw-r--r--mm/vmstat.c84
1 files changed, 84 insertions, 0 deletions
diff --git a/mm/vmstat.c b/mm/vmstat.c
index d3e0fa169f0..23a5899c746 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -16,6 +16,7 @@
#include <linux/cpu.h>
#include <linux/vmstat.h>
#include <linux/sched.h>
+#include <linux/math64.h>
#ifdef CONFIG_VM_EVENT_COUNTERS
DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
@@ -420,6 +421,33 @@ static void fill_contig_page_info(struct zone *zone,
(order - suitable_order);
}
}
+
+/*
+ * A fragmentation index only makes sense if an allocation of a requested
+ * size would fail. If that is true, the fragmentation index indicates
+ * whether external fragmentation or a lack of memory was the problem.
+ * The value can be used to determine if page reclaim or compaction
+ * should be used
+ */
+int fragmentation_index(unsigned int order, struct contig_page_info *info)
+{
+ unsigned long requested = 1UL << order;
+
+ if (!info->free_blocks_total)
+ return 0;
+
+ /* Fragmentation index only makes sense when a request would fail */
+ if (info->free_blocks_suitable)
+ return -1000;
+
+ /*
+ * Index is between 0 and 1 so return within 3 decimal places
+ *
+ * 0 => allocation would fail due to lack of memory
+ * 1 => allocation would fail due to fragmentation
+ */
+ return 1000 - div_u64( (1000+(div_u64(info->free_pages * 1000ULL, requested))), info->free_blocks_total);
+}
#endif
#if defined(CONFIG_PROC_FS) || defined(CONFIG_COMPACTION)
@@ -1087,6 +1115,58 @@ static const struct file_operations unusable_file_ops = {
.release = seq_release,
};
+static void extfrag_show_print(struct seq_file *m,
+ pg_data_t *pgdat, struct zone *zone)
+{
+ unsigned int order;
+ int index;
+
+ /* Alloc on stack as interrupts are disabled for zone walk */
+ struct contig_page_info info;
+
+ seq_printf(m, "Node %d, zone %8s ",
+ pgdat->node_id,
+ zone->name);
+ for (order = 0; order < MAX_ORDER; ++order) {
+ fill_contig_page_info(zone, order, &info);
+ index = fragmentation_index(order, &info);
+ seq_printf(m, "%d.%03d ", index / 1000, index % 1000);
+ }
+
+ seq_putc(m, '\n');
+}
+
+/*
+ * Display fragmentation index for orders that allocations would fail for
+ */
+static int extfrag_show(struct seq_file *m, void *arg)
+{
+ pg_data_t *pgdat = (pg_data_t *)arg;
+
+ walk_zones_in_node(m, pgdat, extfrag_show_print);
+
+ return 0;
+}
+
+static const struct seq_operations extfrag_op = {
+ .start = frag_start,
+ .next = frag_next,
+ .stop = frag_stop,
+ .show = extfrag_show,
+};
+
+static int extfrag_open(struct inode *inode, struct file *file)
+{
+ return seq_open(file, &extfrag_op);
+}
+
+static const struct file_operations extfrag_file_ops = {
+ .open = extfrag_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
static int __init extfrag_debug_init(void)
{
extfrag_debug_root = debugfs_create_dir("extfrag", NULL);
@@ -1097,6 +1177,10 @@ static int __init extfrag_debug_init(void)
extfrag_debug_root, NULL, &unusable_file_ops))
return -ENOMEM;
+ if (!debugfs_create_file("extfrag_index", 0444,
+ extfrag_debug_root, NULL, &extfrag_file_ops))
+ return -ENOMEM;
+
return 0;
}