Simple stupid memory reclaim code

1 files changed, 87 insertions, 0 deletions

diff --git a/linux/shrinker.c b/linux/shrinker.c
new file mode 100644
index 00000000..b8fc2464
--- /dev/null
+++ b/linux/shrinker.c
@@ -0,0 +1,87 @@
+
+#include <stdio.h>
+
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/shrinker.h>
+
+#include "tools-util.h"
+
+static LIST_HEAD(shrinker_list);
+static DEFINE_MUTEX(shrinker_lock);
+
+int register_shrinker(struct shrinker *shrinker)
+{
+	mutex_lock(&shrinker_lock);
+	list_add_tail(&shrinker->list, &shrinker_list);
+	mutex_unlock(&shrinker_lock);
+	return 0;
+}
+
+void unregister_shrinker(struct shrinker *shrinker)
+{
+	mutex_lock(&shrinker_lock);
+	list_del(&shrinker->list);
+	mutex_unlock(&shrinker_lock);
+}
+
+struct meminfo {
+	u64		total;
+	u64		available;
+
+};
+
+static u64 parse_meminfo_line(const char *line)
+{
+	u64 v;
+
+	if (sscanf(line, " %llu kB", &v) < 1)
+		die("sscanf error");
+	return v << 10;
+}
+
+static struct meminfo read_meminfo(void)
+{
+	struct meminfo ret = { 0 };
+	size_t len, n = 0;
+	char *line = NULL;
+	const char *v;
+	FILE *f;
+
+	f = fopen("/proc/meminfo", "r");
+	if (!f)
+		die("error opening /proc/meminfo: %m");
+
+	while ((len = getline(&line, &n, f)) != -1) {
+		if ((v = strcmp_prefix(line, "MemTotal:")))
+			ret.total = parse_meminfo_line(v);
+
+		if ((v = strcmp_prefix(line, "MemAvailable:")))
+			ret.available = parse_meminfo_line(v);
+	}
+
+	fclose(f);
+	free(line);
+
+	return ret;
+}
+
+void run_shrinkers(void)
+{
+	struct shrinker *shrinker;
+	struct meminfo info = read_meminfo();
+	s64 want_shrink = (info.total >> 2) - info.available;
+
+	if (want_shrink <= 0)
+		return;
+
+	mutex_lock(&shrinker_lock);
+	list_for_each_entry(shrinker, &shrinker_list, list) {
+		struct shrink_control sc = {
+			.nr_to_scan = want_shrink >> PAGE_SHIFT
+		};
+
+		shrinker->scan_objects(shrinker, &sc);
+	}
+	mutex_unlock(&shrinker_lock);
+}