mm/low-mem-notify.c - third_party/dump-capture-kernel - Git at Google

 /*
  * mm/low-mem-notify.c
  *
  * Sends low-memory notifications to processes via /dev/low-mem.
  *
  * Copyright (C) 2012 The Chromium OS Authors
  * This program is free software, released under the GPL.
  * Based on a proposal by Minchan Kim
  *
  * A process that polls /dev/low-mem is notified of a low-memory situation.
  * The intent is to allow the process to free some memory before the OOM killer
  * is invoked.
  *
  * A low-memory condition is estimated by subtracting anonymous memory
  * (i.e. process data segments), kernel memory, and a fixed amount of
  * file-backed memory from total memory.  This is just a heuristic, as in
  * general we don't know how much memory can be reclaimed before we try to
  * reclaim it, and that's too expensive or too late.
  *
  * This is tailored to Chromium OS, where a single program (the browser)
  * controls most of the memory, and (currently) no swap space is used.
  */


 #include <linux/low-mem-notify.h>
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/wait.h>
 #include <linux/poll.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/ctype.h>

 #define MB (1 << 20)

 static DECLARE_WAIT_QUEUE_HEAD(low_mem_wait);
 static atomic_t low_mem_state = ATOMIC_INIT(0);
 /* This is a list of thresholds in pages and should be in ascending order. */
 unsigned long low_mem_thresholds[LOW_MEM_THRESHOLD_MAX] = {
 	50 * MB / PAGE_SIZE };
 unsigned int low_mem_threshold_count = 1;

 /* last observed threshold */
 unsigned int low_mem_threshold_last = UINT_MAX;
 bool low_mem_margin_enabled = true;
 unsigned int low_mem_ram_vs_swap_weight = 4;

 /* Limit logging low memory to once per second. */
 DEFINE_RATELIMIT_STATE(low_mem_logging_ratelimit, 1 * HZ, 1);

 unsigned long low_mem_lowest_seen_anon_mem;
 const unsigned long low_mem_anon_mem_delta = 10 * MB / PAGE_SIZE;
 static struct kernfs_node *low_mem_available_dirent;

 struct low_mem_notify_file_info {
 	unsigned long unused;
 };

 void low_mem_notify(void)
 {
 	atomic_set(&low_mem_state, true);
 	wake_up(&low_mem_wait);
 }

 static int low_mem_notify_open(struct inode *inode, struct file *file)
 {
 	struct low_mem_notify_file_info *info;
 	int err = 0;

 	info = kmalloc(sizeof(*info), GFP_KERNEL);
 	if (!info) {
 		err = -ENOMEM;
 		goto out;
 	}

 	file->private_data = info;
 out:
 	return err;
 }

 static int low_mem_notify_release(struct inode *inode, struct file *file)
 {
 	kfree(file->private_data);
 	return 0;
 }

 static unsigned int low_mem_notify_poll(struct file *file, poll_table *wait)
 {
 	unsigned int ret = 0;

 	/* Update state to reflect any recent freeing. */
 	atomic_set(&low_mem_state, low_mem_check());

 	poll_wait(file, &low_mem_wait, wait);

 	if (low_mem_margin_enabled && atomic_read(&low_mem_state) != 0)
 		ret = POLLIN;

 	return ret;
 }

 const struct file_operations low_mem_notify_fops = {
 	.open = low_mem_notify_open,
 	.release = low_mem_notify_release,
 	.poll = low_mem_notify_poll,
 };
 EXPORT_SYMBOL(low_mem_notify_fops);

 #ifdef CONFIG_SYSFS

 #define LOW_MEM_ATTR(_name)				      \
 	static struct kobj_attribute low_mem_##_name##_attr = \
 		__ATTR(_name, 0644, low_mem_##_name##_show,   \
 		       low_mem_##_name##_store)

 static ssize_t low_mem_margin_show(struct kobject *kobj,
 				  struct kobj_attribute *attr, char *buf)
 {
 	if (low_mem_margin_enabled && low_mem_threshold_count) {
 		int i;
 		ssize_t written = 0;

 		for (i = 0; i < low_mem_threshold_count; i++)
 			written += sprintf(buf + written, "%lu ",
 			    low_mem_thresholds[i] * PAGE_SIZE / MB);
 		written += sprintf(buf + written, "\n");
 		return written;
 	} else
 		return sprintf(buf, "off\n");
 }

 static ssize_t low_mem_margin_store(struct kobject *kobj,
 				    struct kobj_attribute *attr,
 				    const char *buf, size_t count)
 {
 	int i = 0, consumed = 0;
 	const char *start = buf;
 	char *endp;
 	unsigned long thresholds[LOW_MEM_THRESHOLD_MAX];

 	memset(thresholds, 0, sizeof(thresholds));
 	/*
 	 * Even though the API does not say anything about this, the string in
 	 * buf is zero-terminated (as long as count < PAGE_SIZE) because buf is
 	 * a newly allocated zero-filled page.  Most other sysfs handlers rely
 	 * on this too.
 	 */
 	if (strncmp("off", buf, 3) == 0) {
 		pr_info("low_mem: disabling notifier\n");
 		low_mem_margin_enabled = false;
 		return count;
 	}
 	if (strncmp("on", buf, 2) == 0) {
 		pr_info("low_mem: enabling notifier\n");
 		low_mem_margin_enabled = true;
 		return count;
 	}
 	/*
 	 * This takes a space separated list of thresholds in ascending order,
 	 * and a trailing newline is optional.
 	 */
 	while (consumed < count) {
 		if (i >= LOW_MEM_THRESHOLD_MAX) {
 			pr_warn("low-mem: too many thresholds");
 			return -EINVAL;
 		}
 		/* special case for trailing newline */
 		if (*start == '\n')
 			break;

 		thresholds[i] = simple_strtoul(start, &endp, 0);
 		if ((endp == start) && *endp != '\n')
 			return -EINVAL;

 		/* make sure each is larger than the last one */
 		if (i && thresholds[i] <= thresholds[i - 1]) {
 			pr_warn("low-mem: thresholds not in increasing order: %lu then %lu\n",
 				thresholds[i - 1], thresholds[i]);
 			return -EINVAL;
 		}

 		if (thresholds[i] * (MB / PAGE_SIZE) > totalram_pages) {
 			pr_warn("low-mem: threshold too high\n");
 			return -EINVAL;
 		}

 		consumed += endp - start + 1;
 		start = endp + 1;
 		i++;
 	}

 	low_mem_threshold_count = i;
 	low_mem_margin_enabled = !!low_mem_threshold_count;

 	/* Convert to pages outside the allocator fast path. */
 	for (i = 0; i < low_mem_threshold_count; i++) {
 		low_mem_thresholds[i] =
 			thresholds[i] * (MB / PAGE_SIZE);
 		pr_info("low_mem: threshold[%d] %lu MB\n", i,
 			low_mem_thresholds[i] * PAGE_SIZE / MB);
 	}

 	return count;
 }
 LOW_MEM_ATTR(margin);

 static ssize_t low_mem_ram_vs_swap_weight_show(struct kobject *kobj,
 					       struct kobj_attribute *attr,
 					       char *buf)
 {
 	return sprintf(buf, "%u\n", low_mem_ram_vs_swap_weight);
 }

 static ssize_t low_mem_ram_vs_swap_weight_store(struct kobject *kobj,
 						struct kobj_attribute *attr,
 						const char *buf, size_t count)
 {
 	unsigned long weight;
 	int err;

 	err = kstrtoul(buf, 10, &weight);
 	if (err)
 		return -EINVAL;
 	/* The special value 0 represents infinity. */
 	low_mem_ram_vs_swap_weight = weight == 0 ?
 		-1U : (unsigned int) weight;
 	pr_info("low_mem: setting ram weight to %u\n",
 		low_mem_ram_vs_swap_weight);
 	return count;
 }
 LOW_MEM_ATTR(ram_vs_swap_weight);

 static ssize_t low_mem_available_show(struct kobject *kobj,
 				      struct kobj_attribute *attr,
 				      char *buf)
 {
 	unsigned long available_mem = get_available_mem_adj();

 	return sprintf(buf, "%lu\n",
 		       available_mem / (MB / PAGE_SIZE));
 }

 static ssize_t low_mem_available_store(struct kobject *kobj,
 				       struct kobj_attribute *attr,
 				       const char *buf, size_t count)
 {
 	return -EINVAL;
 }
 LOW_MEM_ATTR(available);

 static struct attribute *low_mem_attrs[] = {
 	&low_mem_margin_attr.attr,
 	&low_mem_ram_vs_swap_weight_attr.attr,
 	&low_mem_available_attr.attr,
 	NULL,
 };

 static struct attribute_group low_mem_attr_group = {
 	.attrs = low_mem_attrs,
 	.name = "chromeos-low_mem",
 };

 void low_mem_threshold_notify(void)
 {
 	if (low_mem_available_dirent)
 		sysfs_notify_dirent(low_mem_available_dirent);
 }

 static int __init low_mem_init(void)
 {
 	struct kernfs_node *low_mem_node;
 	int err = sysfs_create_group(mm_kobj, &low_mem_attr_group);
 	if (err)
 		pr_err("low_mem: register sysfs failed\n");

 	low_mem_node = sysfs_get_dirent(mm_kobj->sd, "chromeos-low_mem");
 	if (low_mem_node) {
 		low_mem_available_dirent =
 		    sysfs_get_dirent(low_mem_node, "available");
 		sysfs_put(low_mem_node);
 	}

 	if (!low_mem_available_dirent)
 		pr_warn("unable to find dirent for \"available\" attribute\n");

 	low_mem_lowest_seen_anon_mem = totalram_pages;
 	return err;
 }
 module_init(low_mem_init)

 #endif
	/*
	* mm/low-mem-notify.c
	*
	* Sends low-memory notifications to processes via /dev/low-mem.
	*
	* Copyright (C) 2012 The Chromium OS Authors
	* This program is free software, released under the GPL.
	* Based on a proposal by Minchan Kim
	*
	* A process that polls /dev/low-mem is notified of a low-memory situation.
	* The intent is to allow the process to free some memory before the OOM killer
	* is invoked.
	*
	* A low-memory condition is estimated by subtracting anonymous memory
	* (i.e. process data segments), kernel memory, and a fixed amount of
	* file-backed memory from total memory. This is just a heuristic, as in
	* general we don't know how much memory can be reclaimed before we try to
	* reclaim it, and that's too expensive or too late.
	*
	* This is tailored to Chromium OS, where a single program (the browser)
	* controls most of the memory, and (currently) no swap space is used.
	*/


	#include <linux/low-mem-notify.h>
	#include <linux/module.h>
	#include <linux/sched.h>
	#include <linux/wait.h>
	#include <linux/poll.h>
	#include <linux/slab.h>
	#include <linux/mm.h>
	#include <linux/ctype.h>

	#define MB (1 << 20)

	static DECLARE_WAIT_QUEUE_HEAD(low_mem_wait);
	static atomic_t low_mem_state = ATOMIC_INIT(0);
	/* This is a list of thresholds in pages and should be in ascending order. */
	unsigned long low_mem_thresholds[LOW_MEM_THRESHOLD_MAX] = {
	50 * MB / PAGE_SIZE };
	unsigned int low_mem_threshold_count = 1;

	/* last observed threshold */
	unsigned int low_mem_threshold_last = UINT_MAX;
	bool low_mem_margin_enabled = true;
	unsigned int low_mem_ram_vs_swap_weight = 4;

	/* Limit logging low memory to once per second. */
	DEFINE_RATELIMIT_STATE(low_mem_logging_ratelimit, 1 * HZ, 1);

	unsigned long low_mem_lowest_seen_anon_mem;
	const unsigned long low_mem_anon_mem_delta = 10 * MB / PAGE_SIZE;
	static struct kernfs_node *low_mem_available_dirent;

	struct low_mem_notify_file_info {
	unsigned long unused;
	};

	void low_mem_notify(void)
	{
	atomic_set(&low_mem_state, true);
	wake_up(&low_mem_wait);
	}

	static int low_mem_notify_open(struct inode inode, struct file file)
	{
	struct low_mem_notify_file_info *info;
	int err = 0;

	info = kmalloc(sizeof(*info), GFP_KERNEL);
	if (!info) {
	err = -ENOMEM;
	goto out;
	}

	file->private_data = info;
	out:
	return err;
	}

	static int low_mem_notify_release(struct inode inode, struct file file)
	{
	kfree(file->private_data);
	return 0;
	}

	static unsigned int low_mem_notify_poll(struct file file, poll_table wait)
	{
	unsigned int ret = 0;

	/* Update state to reflect any recent freeing. */
	atomic_set(&low_mem_state, low_mem_check());

	poll_wait(file, &low_mem_wait, wait);

	if (low_mem_margin_enabled && atomic_read(&low_mem_state) != 0)
	ret = POLLIN;

	return ret;
	}

	const struct file_operations low_mem_notify_fops = {
	.open = low_mem_notify_open,
	.release = low_mem_notify_release,
	.poll = low_mem_notify_poll,
	};
	EXPORT_SYMBOL(low_mem_notify_fops);

	#ifdef CONFIG_SYSFS

	#define LOW_MEM_ATTR(_name) \
	static struct kobj_attribute low_mem_##_name##_attr = \
	__ATTR(_name, 0644, low_mem_##_name##_show, \
	low_mem_##_name##_store)

	static ssize_t low_mem_margin_show(struct kobject *kobj,
	struct kobj_attribute attr, char buf)
	{
	if (low_mem_margin_enabled && low_mem_threshold_count) {
	int i;
	ssize_t written = 0;

	for (i = 0; i < low_mem_threshold_count; i++)
	written += sprintf(buf + written, "%lu ",
	low_mem_thresholds[i] * PAGE_SIZE / MB);
	written += sprintf(buf + written, "\n");
	return written;
	} else
	return sprintf(buf, "off\n");
	}

	static ssize_t low_mem_margin_store(struct kobject *kobj,
	struct kobj_attribute *attr,
	const char *buf, size_t count)
	{
	int i = 0, consumed = 0;
	const char *start = buf;
	char *endp;
	unsigned long thresholds[LOW_MEM_THRESHOLD_MAX];

	memset(thresholds, 0, sizeof(thresholds));
	/*
	* Even though the API does not say anything about this, the string in
	* buf is zero-terminated (as long as count < PAGE_SIZE) because buf is
	* a newly allocated zero-filled page. Most other sysfs handlers rely
	* on this too.
	*/
	if (strncmp("off", buf, 3) == 0) {
	pr_info("low_mem: disabling notifier\n");
	low_mem_margin_enabled = false;
	return count;
	}
	if (strncmp("on", buf, 2) == 0) {
	pr_info("low_mem: enabling notifier\n");
	low_mem_margin_enabled = true;
	return count;
	}
	/*
	* This takes a space separated list of thresholds in ascending order,
	* and a trailing newline is optional.
	*/
	while (consumed < count) {
	if (i >= LOW_MEM_THRESHOLD_MAX) {
	pr_warn("low-mem: too many thresholds");
	return -EINVAL;
	}
	/* special case for trailing newline */
	if (*start == '\n')
	break;

	thresholds[i] = simple_strtoul(start, &endp, 0);
	if ((endp == start) && *endp != '\n')
	return -EINVAL;

	/* make sure each is larger than the last one */
	if (i && thresholds[i] <= thresholds[i - 1]) {
	pr_warn("low-mem: thresholds not in increasing order: %lu then %lu\n",
	thresholds[i - 1], thresholds[i]);
	return -EINVAL;
	}

	if (thresholds[i] * (MB / PAGE_SIZE) > totalram_pages) {
	pr_warn("low-mem: threshold too high\n");
	return -EINVAL;
	}

	consumed += endp - start + 1;
	start = endp + 1;
	i++;
	}

	low_mem_threshold_count = i;
	low_mem_margin_enabled = !!low_mem_threshold_count;

	/* Convert to pages outside the allocator fast path. */
	for (i = 0; i < low_mem_threshold_count; i++) {
	low_mem_thresholds[i] =
	thresholds[i] * (MB / PAGE_SIZE);
	pr_info("low_mem: threshold[%d] %lu MB\n", i,
	low_mem_thresholds[i] * PAGE_SIZE / MB);
	}

	return count;
	}
	LOW_MEM_ATTR(margin);

	static ssize_t low_mem_ram_vs_swap_weight_show(struct kobject *kobj,
	struct kobj_attribute *attr,
	char *buf)
	{
	return sprintf(buf, "%u\n", low_mem_ram_vs_swap_weight);
	}

	static ssize_t low_mem_ram_vs_swap_weight_store(struct kobject *kobj,
	struct kobj_attribute *attr,
	const char *buf, size_t count)
	{
	unsigned long weight;
	int err;

	err = kstrtoul(buf, 10, &weight);
	if (err)
	return -EINVAL;
	/* The special value 0 represents infinity. */
	low_mem_ram_vs_swap_weight = weight == 0 ?
	-1U : (unsigned int) weight;
	pr_info("low_mem: setting ram weight to %u\n",
	low_mem_ram_vs_swap_weight);
	return count;
	}
	LOW_MEM_ATTR(ram_vs_swap_weight);

	static ssize_t low_mem_available_show(struct kobject *kobj,
	struct kobj_attribute *attr,
	char *buf)
	{
	unsigned long available_mem = get_available_mem_adj();

	return sprintf(buf, "%lu\n",
	available_mem / (MB / PAGE_SIZE));
	}

	static ssize_t low_mem_available_store(struct kobject *kobj,
	struct kobj_attribute *attr,
	const char *buf, size_t count)
	{
	return -EINVAL;
	}
	LOW_MEM_ATTR(available);

	static struct attribute *low_mem_attrs[] = {
	&low_mem_margin_attr.attr,
	&low_mem_ram_vs_swap_weight_attr.attr,
	&low_mem_available_attr.attr,
	NULL,
	};

	static struct attribute_group low_mem_attr_group = {
	.attrs = low_mem_attrs,
	.name = "chromeos-low_mem",
	};

	void low_mem_threshold_notify(void)
	{
	if (low_mem_available_dirent)
	sysfs_notify_dirent(low_mem_available_dirent);
	}

	static int __init low_mem_init(void)
	{
	struct kernfs_node *low_mem_node;
	int err = sysfs_create_group(mm_kobj, &low_mem_attr_group);
	if (err)
	pr_err("low_mem: register sysfs failed\n");

	low_mem_node = sysfs_get_dirent(mm_kobj->sd, "chromeos-low_mem");
	if (low_mem_node) {
	low_mem_available_dirent =
	sysfs_get_dirent(low_mem_node, "available");
	sysfs_put(low_mem_node);
	}

	if (!low_mem_available_dirent)
	pr_warn("unable to find dirent for \"available\" attribute\n");

	low_mem_lowest_seen_anon_mem = totalram_pages;
	return err;
	}
	module_init(low_mem_init)

	#endif