ipvs: add est_cpulist and est_nice sysctl vars

Allow the kthreads for stats to be configured for
specific cpulist (isolation) and niceness (scheduling
priority).

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Cc: yunhong-cgl jiang <xintian1976@gmail.com>
Cc: "dust.li" <dust.li@linux.alibaba.com>
Reviewed-by: Jiri Wiesner <jwiesner@suse.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Documentation/networking/ipvs-sysctl.rst

@@ -129,6 +129,26 @@ drop_packet - INTEGER
 	threshold. When the mode 3 is set, the always mode drop rate
 	is controlled by the /proc/sys/net/ipv4/vs/am_droprate.
 
+est_cpulist - CPULIST
+	Allowed	CPUs for estimation kthreads
+
+	Syntax: standard cpulist format
+	empty list - stop kthread tasks and estimation
+	default - the system's housekeeping CPUs for kthreads
+
+	Example:
+	"all": all possible CPUs
+	"0-N": all possible CPUs, N denotes last CPU number
+	"0,1-N:1/2": first and all CPUs with odd number
+	"": empty list
+
+est_nice - INTEGER
+	default 0
+	Valid range: -20 (more favorable) .. 19 (less favorable)
+
+	Niceness value to use for the estimation kthreads (scheduling
+	priority)
+
 expire_nodest_conn - BOOLEAN
 	- 0 - disabled (default)
 	- not 0 - enabled