mm: reinititalise user and admin reserves if memory is added or removed (1640879a) · Commits · 戴 / test

mm/mmap.c

+74 −2

Original line number	Diff line number	Diff line
		@@ -33,6 +33,8 @@
		#include <linux/uprobes.h>
		#include <linux/rbtree_augmented.h>
		#include <linux/sched/sysctl.h>
		#include <linux/notifier.h>
		#include <linux/memory.h>

		#include <asm/uaccess.h>
		#include <asm/cacheflush.h>
		@@ -3110,7 +3112,7 @@ void __init mmap_init(void)
		* The default value is min(3% of free memory, 128MB)
		* 128MB is enough to recover with sshd/login, bash, and top/kill.
		*/
		static int __meminit init_user_reserve(void)
		static int init_user_reserve(void)
		{
		unsigned long free_kbytes;

		@@ -3131,7 +3133,7 @@ module_init(init_user_reserve)
		* with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
		* only reserve 3% of free pages by default.
		*/
		static int __meminit init_admin_reserve(void)
		static int init_admin_reserve(void)
		{
		unsigned long free_kbytes;

		@@ -3141,3 +3143,73 @@ static int __meminit init_admin_reserve(void)
		return 0;
		}
		module_init(init_admin_reserve)

		/*
		* Reinititalise user and admin reserves if memory is added or removed.
		*
		* The default user reserve max is 128MB, and the default max for the
		* admin reserve is 8MB. These are usually, but not always, enough to
		* enable recovery from a memory hogging process using login/sshd, a shell,
		* and tools like top. It may make sense to increase or even disable the
		* reserve depending on the existence of swap or variations in the recovery
		* tools. So, the admin may have changed them.
		*
		* If memory is added and the reserves have been eliminated or increased above
		* the default max, then we'll trust the admin.
		*
		* If memory is removed and there isn't enough free memory, then we
		* need to reset the reserves.
		*
		* Otherwise keep the reserve set by the admin.
		*/
		static int reserve_mem_notifier(struct notifier_block *nb,
		unsigned long action, void *data)
		{
		unsigned long tmp, free_kbytes;

		switch (action) {
		case MEM_ONLINE:
		/* Default max is 128MB. Leave alone if modified by operator. */
		tmp = sysctl_user_reserve_kbytes;
		if (0 < tmp && tmp < (1UL << 17))
		init_user_reserve();

		/* Default max is 8MB. Leave alone if modified by operator. */
		tmp = sysctl_admin_reserve_kbytes;
		if (0 < tmp && tmp < (1UL << 13))
		init_admin_reserve();

		break;
		case MEM_OFFLINE:
		free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);

		if (sysctl_user_reserve_kbytes > free_kbytes) {
		init_user_reserve();
		pr_info("vm.user_reserve_kbytes reset to %lu\n",
		sysctl_user_reserve_kbytes);
		}

		if (sysctl_admin_reserve_kbytes > free_kbytes) {
		init_admin_reserve();
		pr_info("vm.admin_reserve_kbytes reset to %lu\n",
		sysctl_admin_reserve_kbytes);
		}
		break;
		default:
		break;
		}
		return NOTIFY_OK;
		}

		static struct notifier_block reserve_mem_nb = {
		.notifier_call = reserve_mem_notifier,
		};

		static int __meminit init_reserve_notifier(void)
		{
		if (register_hotmemory_notifier(&reserve_mem_nb))
		printk("Failed registering memory add/remove notifier for admin reserve");

		return 0;
		}
		module_init(init_reserve_notifier)

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