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Commit 5f12733e authored by Michal Hocko's avatar Michal Hocko Committed by Linus Torvalds
Browse files

mm: honor min_free_kbytes set by user 



min_free_kbytes is updated during memory hotplug (by
init_per_zone_wmark_min) currently which is right thing to do in most
cases but this could be unexpected if admin increased the value to
prevent from allocation failures and the new min_free_kbytes would be
decreased as a result of memory hotadd.

This patch saves the user defined value and allows updating
min_free_kbytes only if it is higher than the saved one.

A warning is printed when the new value is ignored.

Signed-off-by: default avatarMichal Hocko <mhocko@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: default avatarZhang Yanfei <zhangyanfei@cn.fujitsu.com>
Acked-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 465939a1

mm/page_alloc.c

+17 −7
Original line number Diff line number Diff line
@@ -204,6 +204,7 @@ static char * const zone_names[MAX_NR_ZONES] = { 
};



int min_free_kbytes = 1024;

int user_min_free_kbytes;



static unsigned long __meminitdata nr_kernel_pages;

static unsigned long __meminitdata nr_all_pages;
@@ -5589,14 +5590,21 @@ static void __meminit setup_per_zone_inactive_ratio(void) 
int __meminit init_per_zone_wmark_min(void)

{

	unsigned long lowmem_kbytes;

	int new_min_free_kbytes;



	lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);

	new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16);



	min_free_kbytes = int_sqrt(lowmem_kbytes * 16);

	if (new_min_free_kbytes > user_min_free_kbytes) {

		min_free_kbytes = new_min_free_kbytes;

		if (min_free_kbytes < 128)

			min_free_kbytes = 128;

		if (min_free_kbytes > 65536)

			min_free_kbytes = 65536;

	} else {

		pr_warn("min_free_kbytes is not updated to %d because user defined value %d is preferred\n",

				new_min_free_kbytes, user_min_free_kbytes);

	}

	setup_per_zone_wmarks();

	refresh_zone_stat_thresholds();

	setup_per_zone_lowmem_reserve();
@@ -5614,8 +5622,10 @@ int min_free_kbytes_sysctl_handler(ctl_table *table, int write, 
	void __user *buffer, size_t *length, loff_t *ppos)

{

	proc_dointvec(table, write, buffer, length, ppos);

	if (write)

	if (write) {

		user_min_free_kbytes = min_free_kbytes;

		setup_per_zone_wmarks();

	}

	return 0;

}