[RESEND PATCH] lparstat: Fix negative values seen while running lparstat with -E option

[Sathvika Vasireddy]

Negative values are seen while running lparstat with -E option.
This is because delta_purr value is less than delta_idle_purr.
Given that these values are read from different sources, a
small variation in the values is possible. So, in such cases,
round down delta_idle_purr to delta_purr.

Without this patch:
=====
System Configuration
type=Dedicated mode=Capped smt=8 lcpu=240 mem=67033290112 kB cpus=0
ent=240.00

---Actual--- -Normalized-
%busy %idle Frequency %busy %idle
------ ------ ------------- ------ ------
-0.03 100.02 3.93GHz[111%] 0.01 110.97
0.00 100.00 3.93GHz[111%] 0.01 110.99
-0.04 100.03 3.93GHz[111%] 0.01 110.98
0.06 99.95 3.93GHz[111%] 0.01 110.99
0.02 99.98 3.93GHz[111%] 0.01 110.99
=====

With this patch:
=====
System Configuration
type=Dedicated mode=Capped smt=8 lcpu=240 mem=67033290112 kB cpus=0
ent=240.00

---Actual--- -Normalized-
%busy %idle Frequency %busy %idle
------ ------ ------------- ------ ------
0.03 99.96 3.93GHz[111%] 0.01 110.98
0.00 100.00 3.93GHz[111%] 0.01 110.99
0.03 99.97 3.93GHz[111%] 0.01 110.99
0.00 100.00 3.93GHz[111%] 0.01 110.99
0.09 99.90 3.93GHz[111%] 0.01 110.99
=====

Reported-by: Shirisha Ganta <shirish...@ibm.com>
Signed-off-by: Sathvika Vasireddy <s...@linux.ibm.com>

---
Resend:
- No code changes, just resending.
---
src/lparstat.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/src/lparstat.c b/src/lparstat.c
index 0b30fc9..5f03fd3 100644
--- a/src/lparstat.c
+++ b/src/lparstat.c
@@ -492,6 +492,15 @@ void get_cpu_util_purr(struct sysentry *unused_se, char *buf)
delta_purr = get_delta_value("purr");
delta_idle_purr = get_delta_value("idle_purr");

+ /*
+ * Given that these values are read from different
+ * sources (purr from lparcfg and idle_purr from sysfs),
+ * a small variation in the values is possible.
+ * In such cases, round down delta_idle_purr to delta_purr.
+ */
+ if (delta_idle_purr > delta_purr)
+ delta_idle_purr = delta_purr;
+
physc = (delta_purr - delta_idle_purr) / delta_tb;
physc *= 100.00;

@@ -507,6 +516,15 @@ void get_cpu_idle_purr(struct sysentry *unused_se, char *buf)
delta_purr = get_delta_value("purr");
delta_idle_purr = get_delta_value("idle_purr");

+ /*
+ * Given that these values are read from different
+ * sources (purr from lparcfg and idle_purr from sysfs),
+ * a small variation in the values is possible.
+ * In such cases, round down delta_idle_purr to delta_purr.
+ */
+ if (delta_idle_purr > delta_purr)
+ delta_idle_purr = delta_purr;
+
physc = (delta_purr - delta_idle_purr) / delta_tb;
idle = (delta_purr / delta_tb) - physc;
idle *= 100.00;
--
2.31.1

[Tyrel Datwyler]

Patch applied to powerpc-utils/next branch.

https://github.com/ibm-power-utilities/powerpc-utils/commit/73ba26c1240a25e7699449e82cfc09dad10fed80

Thanks,
-Tyrel