The patch titled
Subject: mm/vmstat: defer the refresh_zone_stat_thresholds after all CPUs bringup
has been added to the -mm mm-unstable branch. Its filename is
mm-vmstat-defer-the-refresh_zone_stat_thresholds-after-all-cpus-bringup.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmstat-defer-the-refresh_zone_stat_thresholds-after-all-cpus-bringup.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
Subject: mm/vmstat: defer the refresh_zone_stat_thresholds after all CPUs bringup
Date: Fri, 5 Jul 2024 01:48:21 -0700
refresh_zone_stat_thresholds function has two loops which is expensive for
higher number of CPUs and NUMA nodes.
Below is the rough estimation of total iterations done by these loops
based on number of NUMA and CPUs.
Total number of iterations: nCPU * 2 * Numa * mCPU
Where:
nCPU = total number of CPUs
Numa = total number of NUMA nodes
mCPU = mean value of total CPUs (e.g., 512 for 1024 total CPUs)
For the system under test with 16 NUMA nodes and 1024 CPUs, this results
in a substantial increase in the number of loop iterations during boot-up
when NUMA is enabled:
No NUMA = 1024*2*1*512 = 1,048,576 : Here refresh_zone_stat_thresholds
takes around 224 ms total for all the CPUs in the system under test.
16 NUMA = 1024*2*16*512 = 16,777,216 : Here refresh_zone_stat_thresholds
takes around 4.5 seconds total for all the CPUs in the system under test.
Calling this for each CPU is expensive when there are large number of CPUs
along with multiple NUMAs. Fix this by deferring
refresh_zone_stat_thresholds to be called later at once when all the
secondary CPUs are up. Also, register the DYN hooks to keep the existing
hotplug functionality intact.
Link: https://lkml.kernel.org/r/1720169301-21002-1-git-send-email-ssengar@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
Cc: Wei Liu <wei.liu@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmstat.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
--- a/mm/vmstat.c~mm-vmstat-defer-the-refresh_zone_stat_thresholds-after-all-cpus-bringup
+++ a/mm/vmstat.c
@@ -31,6 +31,7 @@
#include "internal.h"
+static int vmstat_late_init_done;
#ifdef CONFIG_NUMA
int sysctl_vm_numa_stat = ENABLE_NUMA_STAT;
@@ -2130,7 +2131,8 @@ static void __init init_cpu_node_state(v
static int vmstat_cpu_online(unsigned int cpu)
{
- refresh_zone_stat_thresholds();
+ if (vmstat_late_init_done)
+ refresh_zone_stat_thresholds();
if (!node_state(cpu_to_node(cpu), N_CPU)) {
node_set_state(cpu_to_node(cpu), N_CPU);
@@ -2162,6 +2164,14 @@ static int vmstat_cpu_dead(unsigned int
return 0;
}
+static int __init vmstat_late_init(void)
+{
+ refresh_zone_stat_thresholds();
+ vmstat_late_init_done = 1;
+
+ return 0;
+}
+late_initcall(vmstat_late_init);
#endif
struct workqueue_struct *mm_percpu_wq;
_
Patches currently in -mm which might be from ssengar@xxxxxxxxxxxxxxxxxxx are
mm-vmstat-defer-the-refresh_zone_stat_thresholds-after-all-cpus-bringup.patch
