This patch makes new device file "/dev/low_mem_notify". If application polls it, it can receive event when system memory pressure happens. This patch is based on KOSAKI and Marcelo's long time ago work. http://lwn.net/Articles/268732/ Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> --- drivers/char/mem.c | 7 ++++ include/linux/low_mem_notify.h | 6 ++++ mm/Kconfig | 7 ++++ mm/Makefile | 1 + mm/low_mem_notify.c | 61 ++++++++++++++++++++++++++++++++++++++++ 5 files changed, 82 insertions(+), 0 deletions(-) create mode 100644 include/linux/low_mem_notify.h create mode 100644 mm/low_mem_notify.c diff --git a/drivers/char/mem.c b/drivers/char/mem.c index d6e9d08..72bc12b 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -35,6 +35,10 @@ # include <linux/efi.h> #endif +#ifdef CONFIG_LOW_MEM_NOTIFY +extern struct file_operations low_mem_notify_fops; +#endif + static inline unsigned long size_inside_page(unsigned long start, unsigned long size) { @@ -867,6 +871,9 @@ static const struct memdev { #ifdef CONFIG_CRASH_DUMP [12] = { "oldmem", 0, &oldmem_fops, NULL }, #endif +#ifdef CONFIG_LOW_MEM_NOTIFY + [13] = { "low_mem_notify",0666, &low_mem_notify_fops, NULL}, +#endif }; static int memory_open(struct inode *inode, struct file *filp) diff --git a/include/linux/low_mem_notify.h b/include/linux/low_mem_notify.h new file mode 100644 index 0000000..bc0fc89 --- /dev/null +++ b/include/linux/low_mem_notify.h @@ -0,0 +1,6 @@ +#ifndef _LINUX_LOW_MEM_NOTIFY_H +#define _LINUX_LOW_MEM_NOTIFY_H + +void low_memory_pressure(void); + +#endif diff --git a/mm/Kconfig b/mm/Kconfig index e338407..a2f48c6 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -379,3 +379,10 @@ config CLEANCACHE in a negligible performance hit. If unsure, say Y to enable cleancache + +config LOW_MEM_NOTIFY + bool "Enable low memory notification" + default n + help + If system suffer from low memory, kernel can notify it to user through + /dev/low_mem_notify. diff --git a/mm/Makefile b/mm/Makefile index 50ec00e..7856357 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -51,3 +51,4 @@ obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o obj-$(CONFIG_CLEANCACHE) += cleancache.o +obj-$(CONFIG_LOW_MEM_NOTIFY) += low_mem_notify.o diff --git a/mm/low_mem_notify.c b/mm/low_mem_notify.c new file mode 100644 index 0000000..7432307 --- /dev/null +++ b/mm/low_mem_notify.c @@ -0,0 +1,61 @@ +#include <linux/module.h> +#include <linux/sched.h> +#include <linux/wait.h> +#include <linux/poll.h> +#include <linux/slab.h> + +static DECLARE_WAIT_QUEUE_HEAD(low_mem_wait); +static atomic_t nr_low_mem = ATOMIC_INIT(0); + +struct low_mem_notify_file_info { + unsigned long last_proc_notify; +}; + +void low_memory_pressure(void) +{ + atomic_inc(&nr_low_mem); + 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; + + poll_wait(file, &low_mem_wait, wait); + + if (atomic_read(&nr_low_mem) != 0) { + ret = POLLIN; + atomic_set(&nr_low_mem, 0); + } + + return ret; +} + +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); -- 1.7.7.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>