From 86aaf255437af88c0ff5d20a3c98e2b42fb0beda Mon Sep 17 00:00:00 2001 From: Baoquan He Date: Wed, 3 Jun 2020 15:58:48 -0700 Subject: [PATCH] mm/page_alloc.c: only tune sysctl_lowmem_reserve_ratio value once when changing it Patch series "improvements about lowmem_reserve and /proc/zoneinfo", v2. This patch (of 3): When people write to /proc/sys/vm/lowmem_reserve_ratio to change sysctl_lowmem_reserve_ratio[], setup_per_zone_lowmem_reserve() is called to recalculate all ->lowmem_reserve[] for each zone of all nodes as below: static void setup_per_zone_lowmem_reserve(void) { ... for_each_online_pgdat(pgdat) { for (j = 0; j < MAX_NR_ZONES; j++) { ... while (idx) { ... if (sysctl_lowmem_reserve_ratio[idx] < 1) { sysctl_lowmem_reserve_ratio[idx] = 0; lower_zone->lowmem_reserve[j] = 0; } else { ... } } } } Meanwhile, here, sysctl_lowmem_reserve_ratio[idx] will be tuned if its value is smaller than '1'. As we know, sysctl_lowmem_reserve_ratio[] is set for zone without regarding to which node it belongs to. That means the tuning will be done on all nodes, even though it has been done in the first node. And the tuning will be done too even when init_per_zone_wmark_min() calls setup_per_zone_lowmem_reserve(), where actually nobody tries to change sysctl_lowmem_reserve_ratio[]. So now move the tuning into lowmem_reserve_ratio_sysctl_handler(), to make code logic more reasonable. Signed-off-by: Baoquan He Signed-off-by: Andrew Morton Cc: Joonsoo Kim Cc: Michal Hocko Cc: Baoquan He Cc: Mel Gorman Cc: David Rientjes Link: http://lkml.kernel.org/r/20200402140113.3696-1-bhe@redhat.com Link: http://lkml.kernel.org/r/20200402140113.3696-2-bhe@redhat.com Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a1a4f88..f3d5f0e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7704,8 +7704,7 @@ static void setup_per_zone_lowmem_reserve(void) idx--; lower_zone = pgdat->node_zones + idx; - if (sysctl_lowmem_reserve_ratio[idx] < 1) { - sysctl_lowmem_reserve_ratio[idx] = 0; + if (!sysctl_lowmem_reserve_ratio[idx]) { lower_zone->lowmem_reserve[j] = 0; } else { lower_zone->lowmem_reserve[j] = @@ -7970,7 +7969,15 @@ int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write, int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *table, int write, void __user *buffer, size_t *length, loff_t *ppos) { + int i; + proc_dointvec_minmax(table, write, buffer, length, ppos); + + for (i = 0; i < MAX_NR_ZONES; i++) { + if (sysctl_lowmem_reserve_ratio[i] < 1) + sysctl_lowmem_reserve_ratio[i] = 0; + } + setup_per_zone_lowmem_reserve(); return 0; } -- 2.7.4