linux-kernel - [PATCH RFC 1/3] Add a sysctl interface to control and report the cpu entitlement setting.

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Date:	Thu, 23 Aug 2012 18:14:26 -0500
From:	Michael Wolf <mjw@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org, peterz@...radead.org, mtosatti@...hat.com,
	glommer@...allels.com, mingo@...hat.com, avi@...hat.com
Subject: [PATCH RFC 1/3] Add a sysctl interface to control and report the cpu
 entitlement setting.

This setting will later be used to compute an expected steal time.

Signed-off-by: Michael Wolf <mjw@...ux.vnet.ibm.com>
---
 Documentation/sysctl/kernel.txt |   14 ++++++++++++++
 fs/proc/stat.c                  |    1 +
 kernel/sysctl.c                 |   10 ++++++++++
 3 files changed, 25 insertions(+)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 6d78841..0f617dc 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -28,6 +28,7 @@ show up in /proc/sys/kernel:
 - core_pattern
 - core_pipe_limit
 - core_uses_pid
+- cpu_entitlement
 - ctrl-alt-del
 - dmesg_restrict
 - domainname
@@ -226,6 +227,19 @@ the filename.
 
 ==============================================================
 
+cpu_entitlement:
+
+The cpu_entitlement is the percentage of cpu utilization that
+the system expects to receive.  By default this is set to 100,
+in a guest system this could be set to a value between 0 and 100.
+This value is used to adjust the amount of steal time that
+process accounting code in the guest will display. The end effect
+will be is that steal time will only be reported if the
+percentage of steal time is greater than 100 - cpu_entitlement
+value.
+
+==============================================================
+
 ctrl-alt-del:
 
 When the value in this file is 0, ctrl-alt-del is trapped and
diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index 64c3b31..14e26c8 100644
--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -12,6 +12,7 @@
 #include <asm/cputime.h>
 #include <linux/tick.h>
 
+int cpu_entitlement = 100;
 #ifndef arch_irq_stat_cpu
 #define arch_irq_stat_cpu(cpu) 0
 #endif
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 87174ef..85efbc2 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -109,6 +109,7 @@ extern int percpu_pagelist_fraction;
 extern int compat_log;
 extern int latencytop_enabled;
 extern int sysctl_nr_open_min, sysctl_nr_open_max;
+extern int cpu_entitlement;
 #ifndef CONFIG_MMU
 extern int sysctl_nr_trim_pages;
 #endif
@@ -673,6 +674,15 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
+	{
+		.procname	= "cpu_entitlement",
+		.data		= &cpu_entitlement,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &one_hundred,
+	},
 #if defined CONFIG_PRINTK
 	{
 		.procname	= "printk",

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