[PATCH] net: ipvs: add sysctl_run_estimation to support disable estimation

[Dust Li <dust.li@xxxxxxxxxxxxxxxxx>]

fix #31562403

estimation_timer will iterater the est_list to do estimation
for each ipvs stats. When there are lots of services, the
list can be very large.
We observiced estimation_timer() run for more then 200ms on
a machine with 104 CPU and 50K services.

yunhong-cgl jiang report the same phenomenon before:
https://www.spinics.net/lists/lvs-devel/msg05426.html

In some cases(for example a large K8S cluster with many ipvs services),
ipvs estimation may not be needed. So adding a sysctl blob to allow
users to disable this completely.

Default is: 1 (enable)

Signed-off-by: Dust Li <dust.li@xxxxxxxxxxxxxxxxx>
---
 Documentation/networking/ipvs-sysctl.rst | 17 ++++++
 include/net/ip_vs.h                      |  3 +
 net/netfilter/ipvs/ip_vs_est.c           | 73 ++++++++++++++++++++++++
 3 files changed, 93 insertions(+)

diff --git a/Documentation/networking/ipvs-sysctl.rst 
b/Documentation/networking/ipvs-sysctl.rst
index 2afccc63856e..e20f7a27fc85 100644
--- a/Documentation/networking/ipvs-sysctl.rst
+++ b/Documentation/networking/ipvs-sysctl.rst
@@ -300,3 +300,20 @@ sync_version - INTEGER
 
        Kernels with this sync_version entry are able to receive messages
        of both version 1 and version 2 of the synchronisation protocol.
+
+run_estimation - BOOLEAN
+       0 - disabled
+       not 0 - enabled (default)
+
+       If disabled, the estimation will be stop, and you can't see
+       any update on speed estimation data.
+
+       For example
+       'Conns/s   Pkts/s   Pkts/s          Bytes/s          Bytes/s'
+       those data in /proc/net/ip_vs_stats will always be zero.
+       Note, this only affect the speed estimation, the total data
+       will still be updated.
+
+       You can always re-enable estimation by setting this value to 1.
+       But be carefull, the first estimation after re-enable is not
+       accurate.
diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index d609e957a3ec..6cbb3a08b176 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -941,6 +941,9 @@ struct netns_ipvs {
        struct ctl_table_header *lblcr_ctl_header;
        struct ctl_table        *lblcr_ctl_table;
        /* ip_vs_est */
+       int                     sysctl_run_estimation;
+       struct ctl_table_header *est_ctl_header;
+       struct ctl_table        *est_ctl_table;
        struct list_head        est_list;       /* estimator list */
        spinlock_t              est_lock;
        struct timer_list       est_timer;      /* Estimation timer */
diff --git a/net/netfilter/ipvs/ip_vs_est.c b/net/netfilter/ipvs/ip_vs_est.c
index 05b8112ffb37..6709796b8621 100644
--- a/net/netfilter/ipvs/ip_vs_est.c
+++ b/net/netfilter/ipvs/ip_vs_est.c
@@ -100,6 +100,9 @@ static void estimation_timer(struct timer_list *t)
        u64 rate;
        struct netns_ipvs *ipvs = from_timer(ipvs, t, est_timer);
 
+       if (!ipvs->sysctl_run_estimation)
+               goto skip;
+
        spin_lock(&ipvs->est_lock);
        list_for_each_entry(e, &ipvs->est_list, list) {
                s = container_of(e, struct ip_vs_stats, est);
@@ -131,6 +134,8 @@ static void estimation_timer(struct timer_list *t)
                spin_unlock(&s->lock);
        }
        spin_unlock(&ipvs->est_lock);
+
+skip:
        mod_timer(&ipvs->est_timer, jiffies + 2*HZ);
 }
 
@@ -184,10 +189,77 @@ void ip_vs_read_estimator(struct ip_vs_kstats *dst, 
struct ip_vs_stats *stats)
        dst->outbps = (e->outbps + 0xF) >> 5;
 }
 
+#ifdef CONFIG_SYSCTL
+/* IPVS ESTIMATION sysctl table */
+static struct ctl_table vs_vars_table[] = {
+       {
+               .procname       = "run_estimation",
+               .data           = NULL,
+               .maxlen         = sizeof(int),
+               .mode           = 0644,
+               .proc_handler   = proc_dointvec,
+       },
+       { }
+};
+
+static int ip_vs_est_sysctl_init(struct netns_ipvs *ipvs)
+{
+       struct net *net = ipvs->net;
+
+       if (!net_eq(net, &init_net)) {
+               ipvs->est_ctl_table = kmemdup(vs_vars_table,
+                                             sizeof(vs_vars_table),
+                                             GFP_KERNEL);
+               if (!ipvs->est_ctl_table)
+                       return -ENOMEM;
+
+               /* Don't export sysctls to unprivileged users */
+               if (net->user_ns != &init_user_ns)
+                       ipvs->est_ctl_table[0].procname = NULL;
+
+       } else {
+               ipvs->est_ctl_table = vs_vars_table;
+       }
+
+       ipvs->sysctl_run_estimation = 1;
+       ipvs->est_ctl_table[0].data = &ipvs->sysctl_run_estimation;
+
+       ipvs->est_ctl_header =
+               register_net_sysctl(net, "net/ipv4/vs", ipvs->est_ctl_table);
+       if (!ipvs->est_ctl_header) {
+               if (!net_eq(net, &init_net))
+                       kfree(ipvs->est_ctl_table);
+               return -ENOMEM;
+       }
+
+       return 0;
+}
+
+static void ip_vs_est_sysctl_cleanup(struct netns_ipvs *ipvs)
+{
+       unregister_net_sysctl_table(ipvs->est_ctl_header);
+
+       if (!net_eq(ipvs->net, &init_net))
+               kfree(ipvs->est_ctl_table);
+}
+
+#else
+
+static int ip_vs_est_sysctl_init(struct netns_ipvs *ipvs)
+{
+       ipvs->sysctl_run_estimation = 1;
+       return 0;
+}
+
+static void ip_vs_est_sysctl_cleanup(struct netns_ipvs *ipvs) { }
+
+#endif
+
 int __net_init ip_vs_estimator_net_init(struct netns_ipvs *ipvs)
 {
        INIT_LIST_HEAD(&ipvs->est_list);
        spin_lock_init(&ipvs->est_lock);
+       ip_vs_est_sysctl_init(ipvs);
        timer_setup(&ipvs->est_timer, estimation_timer, 0);
        mod_timer(&ipvs->est_timer, jiffies + 2 * HZ);
        return 0;
@@ -196,4 +268,5 @@ int __net_init ip_vs_estimator_net_init(struct netns_ipvs 
*ipvs)
 void __net_exit ip_vs_estimator_net_cleanup(struct netns_ipvs *ipvs)
 {
        del_timer_sync(&ipvs->est_timer);
+       ip_vs_est_sysctl_cleanup(ipvs);
 }
-- 
2.19.1.3.ge56e4f7