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: Michal Hocko <mhocko@xxxxxxx>
---
mm/page_alloc.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 22c528e..a785fad 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -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;
@@ -5592,14 +5593,22 @@ 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);
-
- min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
- if (min_free_kbytes < 128)
- min_free_kbytes = 128;
- if (min_free_kbytes > 65536)
- min_free_kbytes = 65536;
+ new_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 {
+ printk(KERN_WARNING "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();
@@ -5617,8 +5626,10 @@ 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;
}
--
1.8.3.1
--
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