Staging: android: add lowmemorykiller driver

From: San Mehat <san@android.com>
Cc: Brian Swetland <swetland@google.com>
Cc: Robert Love <rlove@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/android/Kconfig

@@ -77,4 +77,10 @@ config ANDROID_TIMED_GPIO
 	depends on GENERIC_GPIO
 	default n
 
+config ANDROID_LOW_MEMORY_KILLER
+	bool "Android Low Memory Killer"
+	default N
+	---help---
+	  Register processes to be killed when memory is low
+
 endmenu

drivers/staging/android/Makefile

@@ -2,3 +2,4 @@ obj-$(CONFIG_ANDROID_BINDER_IPC)	+= binder.o
 obj-$(CONFIG_ANDROID_LOGGER)		+= logger.o
 obj-$(CONFIG_ANDROID_RAM_CONSOLE)	+= ram_console.o
 obj-$(CONFIG_ANDROID_TIMED_GPIO)	+= timed_gpio.o
+obj-$(CONFIG_ANDROID_LOW_MEMORY_KILLER)	+= lowmemorykiller.o

drivers/staging/android/lowmemorykiller.c

@@ -0,0 +1,119 @@
+/* drivers/misc/lowmemorykiller.c
+ *
+ * Copyright (C) 2007-2008 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/oom.h>
+#include <linux/sched.h>
+
+static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask);
+
+static struct shrinker lowmem_shrinker = {
+	.shrink = lowmem_shrink,
+	.seeks = DEFAULT_SEEKS * 16
+};
+static uint32_t lowmem_debug_level = 2;
+static int lowmem_adj[6] = {
+	0,
+	1,
+	6,
+	12,
+};
+static int lowmem_adj_size = 4;
+static size_t lowmem_minfree[6] = {
+	3*512, // 6MB
+	2*1024, // 8MB
+	4*1024, // 16MB
+	16*1024, // 64MB
+};
+static int lowmem_minfree_size = 4;
+
+#define lowmem_print(level, x...) do { if(lowmem_debug_level >= (level)) printk(x); } while(0)
+
+module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
+module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size, S_IRUGO | S_IWUSR);
+module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size, S_IRUGO | S_IWUSR);
+module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
+
+static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask)
+{
+	struct task_struct *p;
+	struct task_struct *selected = NULL;
+	int rem = 0;
+	int tasksize;
+	int i;
+	int min_adj = OOM_ADJUST_MAX + 1;
+	int selected_tasksize = 0;
+	int array_size = ARRAY_SIZE(lowmem_adj);
+	int other_free = global_page_state(NR_FREE_PAGES) + global_page_state(NR_FILE_PAGES);
+	if(lowmem_adj_size < array_size)
+		array_size = lowmem_adj_size;
+	if(lowmem_minfree_size < array_size)
+		array_size = lowmem_minfree_size;
+	for(i = 0; i < array_size; i++) {
+		if(other_free < lowmem_minfree[i]) {
+			min_adj = lowmem_adj[i];
+			break;
+		}
+	}
+	if(nr_to_scan > 0)
+		lowmem_print(3, "lowmem_shrink %d, %x, ofree %d, ma %d\n", nr_to_scan, gfp_mask, other_free, min_adj);
+	read_lock(&tasklist_lock);
+	for_each_process(p) {
+		if(p->oomkilladj >= 0 && p->mm) {
+			tasksize = get_mm_rss(p->mm);
+			if(nr_to_scan > 0 && tasksize > 0 && p->oomkilladj >= min_adj) {
+				if(selected == NULL ||
+				   p->oomkilladj > selected->oomkilladj ||
+				   (p->oomkilladj == selected->oomkilladj &&
+				    tasksize > selected_tasksize)) {
+					selected = p;
+					selected_tasksize = tasksize;
+					lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
+					             p->pid, p->comm, p->oomkilladj, tasksize);
+				}
+			}
+			rem += tasksize;
+		}
+	}
+	if(selected != NULL) {
+		lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
+		             selected->pid, selected->comm,
+		             selected->oomkilladj, selected_tasksize);
+		force_sig(SIGKILL, selected);
+		rem -= selected_tasksize;
+	}
+	lowmem_print(4, "lowmem_shrink %d, %x, return %d\n", nr_to_scan, gfp_mask, rem);
+	read_unlock(&tasklist_lock);
+	return rem;
+}
+
+static int __init lowmem_init(void)
+{
+	register_shrinker(&lowmem_shrinker);
+	return 0;
+}
+
+static void __exit lowmem_exit(void)
+{
+	unregister_shrinker(&lowmem_shrinker);
+}
+
+module_init(lowmem_init);
+module_exit(lowmem_exit);
+
+MODULE_LICENSE("GPL");
+