Re: [PATCH v2 1/6] mm/page_alloc: recalculate some of zone threshold when on/offline memory

From: Rui Teng
Date: Thu Apr 28 2016 - 03:46:58 EST


On 4/25/16 1:21 PM, js1304@xxxxxxxxx wrote:
From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

Some of zone threshold depends on number of managed pages in the zone.
When memory is going on/offline, it can be changed and we need to
adjust them.

This patch add recalculation to appropriate places and clean-up
related function for better maintanance.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
---
mm/page_alloc.c | 36 +++++++++++++++++++++++++++++-------
1 file changed, 29 insertions(+), 7 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 71fa015..ffa93e0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4633,6 +4633,8 @@ int local_memory_node(int node)
}
#endif

+static void setup_min_unmapped_ratio(struct zone *zone);
+static void setup_min_slab_ratio(struct zone *zone);
#else /* CONFIG_NUMA */

static void set_zonelist_order(void)
@@ -5747,9 +5749,8 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat)
zone->managed_pages = is_highmem_idx(j) ? realsize : freesize;
#ifdef CONFIG_NUMA
zone->node = nid;
- zone->min_unmapped_pages = (freesize*sysctl_min_unmapped_ratio)
- / 100;
- zone->min_slab_pages = (freesize * sysctl_min_slab_ratio) / 100;
+ setup_min_unmapped_ratio(zone);
+ setup_min_slab_ratio(zone);

The original logic use freesize to calculate the
zone->min_unmapped_pages and zone->min_slab_pages here.
But the new function will use zone->managed_pages.
Do you mean the original logic is wrong, or the managed_pages will
always be freesize when CONFIG_NUMA defined?

#endif
zone->name = zone_names[j];
spin_lock_init(&zone->lock);
@@ -6655,6 +6656,7 @@ int __meminit init_per_zone_wmark_min(void)
{
unsigned long lowmem_kbytes;
int new_min_free_kbytes;
+ struct zone *zone;

lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);
new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
@@ -6672,6 +6674,14 @@ int __meminit init_per_zone_wmark_min(void)
setup_per_zone_wmarks();
refresh_zone_stat_thresholds();
setup_per_zone_lowmem_reserve();
+
+ for_each_zone(zone) {
+#ifdef CONFIG_NUMA
+ setup_min_unmapped_ratio(zone);
+ setup_min_slab_ratio(zone);
+#endif
+ }
+
return 0;
}
module_init(init_per_zone_wmark_min)
@@ -6713,6 +6723,12 @@ int watermark_scale_factor_sysctl_handler(struct ctl_table *table, int write,
}

#ifdef CONFIG_NUMA
+static void setup_min_unmapped_ratio(struct zone *zone)
+{
+ zone->min_unmapped_pages = (zone->managed_pages *
+ sysctl_min_unmapped_ratio) / 100;
+}
+
int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *length, loff_t *ppos)
{
@@ -6724,11 +6740,17 @@ int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *table, int write,
return rc;

for_each_zone(zone)
- zone->min_unmapped_pages = (zone->managed_pages *
- sysctl_min_unmapped_ratio) / 100;
+ setup_min_unmapped_ratio(zone);
+
return 0;
}

+static void setup_min_slab_ratio(struct zone *zone)
+{
+ zone->min_slab_pages = (zone->managed_pages *
+ sysctl_min_slab_ratio) / 100;
+}
+
int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *length, loff_t *ppos)
{
@@ -6740,8 +6762,8 @@ int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write,
return rc;

for_each_zone(zone)
- zone->min_slab_pages = (zone->managed_pages *
- sysctl_min_slab_ratio) / 100;
+ setup_min_slab_ratio(zone);
+
return 0;
}
#endif