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 <>
Cc: Mel Gorman <>
Acked-by: default avatarZhang Yanfei <>
Acked-by: default avatarKOSAKI Motohiro <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 465939a1
......@@ -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);
......@@ -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;
return 0;
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