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Date: Thu, 23 Aug 2012 18:14:42 -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 3/3] Modify the amount of stealtime that the kernel
reports via the /proc interface.
Stealtime will be adjusted based on the cpu entitlement setting. The user
will supply the cpu_entitlement which is the percentage of cpu the guest can
expect to receive. The expected steal time is based on the expected steal
percentage which is 100 - cpu_entitlement. If steal_time is less than the
expected steal time that is reported steal_time is changed to 0 no other fields
are changed. If the steal_time is greater than the expected_steal then the
difference is reported. By default the cpu_entitlement will be 100% and the
steal time will be reported without any modification.
Signed-off-by: Michael Wolf <mjw@...ux.vnet.ibm.com>
---
fs/proc/stat.c | 70 ++++++++++++++++++++++++++++++++++++++++++-
include/linux/kernel_stat.h | 2 +
2 files changed, 70 insertions(+), 2 deletions(-)
diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index cf66665..efbaa03 100644
--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -73,6 +73,68 @@ static u64 get_iowait_time(int cpu)
#endif
+/*
+ * This function will alter the steal time value that is written out
+ * to /proc/stat. The cpu_entitlement is set by the user/admin and is
+ * meant to reflect the percentage of the processor that is expected to
+ * be used. So as long as the amount of steal time is less than the
+ * expected steal time (based on cpu_entitlement) then report steal time
+ * as zero.
+ */
+static void kstat_adjust_steal_time(int currcpu)
+{
+ int j;
+ u64 cpustat_delta[NR_STATS];
+ u64 total_elapsed_time;
+ int expected_steal_pct;
+ u64 expected_steal;
+ u64 *currstat, *prevstat;
+
+ /*
+ * if cpu_entitlement = 100% then the expected steal time is 0
+ * so we don't need to do any adjustments to the fields.
+ */
+ if (cpu_entitlement == 100) {
+ kcpustat_cpu(currcpu).cpustat[CPUTIME_ADJ_STEAL] =
+ kcpustat_cpu(currcpu).cpustat[CPUTIME_STEAL];
+ return;
+ }
+ /*
+ * For the user it is more intuitive to think in terms of
+ * cpu entitlement. To do the calculations it is easier to
+ * think in terms of allowed steal time. So convert the percentage
+ * from cpu_entitlement to expected_steal_percent.
+ */
+ expected_steal_pct = 100 - cpu_entitlement;
+
+ total_elapsed_time = 0;
+ /* determine the total time elapsed between calls */
+ currstat = kcpustat_cpu(currcpu).cpustat;
+ prevstat = kcpustat_cpu(currcpu).prev_cpustat;
+ for (j = CPUTIME_USER; j < CPUTIME_GUEST; j++) {
+ cpustat_delta[j] = currstat[j] - prevstat[j];
+ prevstat[j] = currstat[j];
+ total_elapsed_time = total_elapsed_time + cpustat_delta[j];
+ }
+
+ /*
+ * calculate the amount of expected steal time. Add 5 as a
+ * rounding factor.
+ */
+
+ expected_steal = (total_elapsed_time * expected_steal_pct + 5) / 100;
+ if (cpustat_delta[CPUTIME_STEAL] < expected_steal)
+ cpustat_delta[CPUTIME_STEAL] = 0;
+ else
+ cpustat_delta[CPUTIME_STEAL] -= expected_steal;
+
+ /* Adjust the steal time accordingly */
+ currstat[CPUTIME_ADJ_STEAL] = prevstat[CPUTIME_ADJ_STEAL]
+ + cpustat_delta[CPUTIME_STEAL];
+ prevstat[CPUTIME_ADJ_STEAL] = currstat[CPUTIME_ADJ_STEAL];
+}
+
+
static int show_stat(struct seq_file *p, void *v)
{
int i, j;
@@ -90,7 +152,11 @@ static int show_stat(struct seq_file *p, void *v)
getboottime(&boottime);
jif = boottime.tv_sec;
+
for_each_possible_cpu(i) {
+ /* adjust the steal time based on the processor entitlement */
+ kstat_adjust_steal_time(i);
+
user += kcpustat_cpu(i).cpustat[CPUTIME_USER];
nice += kcpustat_cpu(i).cpustat[CPUTIME_NICE];
system += kcpustat_cpu(i).cpustat[CPUTIME_SYSTEM];
@@ -98,7 +164,7 @@ static int show_stat(struct seq_file *p, void *v)
iowait += get_iowait_time(i);
irq += kcpustat_cpu(i).cpustat[CPUTIME_IRQ];
softirq += kcpustat_cpu(i).cpustat[CPUTIME_SOFTIRQ];
- steal += kcpustat_cpu(i).cpustat[CPUTIME_STEAL];
+ steal += kcpustat_cpu(i).cpustat[CPUTIME_ADJ_STEAL];
guest += kcpustat_cpu(i).cpustat[CPUTIME_GUEST];
guest_nice += kcpustat_cpu(i).cpustat[CPUTIME_GUEST_NICE];
sum += kstat_cpu_irqs_sum(i);
@@ -135,7 +201,7 @@ static int show_stat(struct seq_file *p, void *v)
iowait = get_iowait_time(i);
irq = kcpustat_cpu(i).cpustat[CPUTIME_IRQ];
softirq = kcpustat_cpu(i).cpustat[CPUTIME_SOFTIRQ];
- steal = kcpustat_cpu(i).cpustat[CPUTIME_STEAL];
+ steal = kcpustat_cpu(i).cpustat[CPUTIME_ADJ_STEAL];
guest = kcpustat_cpu(i).cpustat[CPUTIME_GUEST];
guest_nice = kcpustat_cpu(i).cpustat[CPUTIME_GUEST_NICE];
seq_printf(p, "cpu%d", i);
diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index bbe5d15..a4f6d1c 100644
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -27,11 +27,13 @@ enum cpu_usage_stat {
CPUTIME_STEAL,
CPUTIME_GUEST,
CPUTIME_GUEST_NICE,
+ CPUTIME_ADJ_STEAL,
NR_STATS,
};
struct kernel_cpustat {
u64 cpustat[NR_STATS];
+ u64 prev_cpustat[NR_STATS];
};
struct kernel_stat {
--
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