[PATCH] lparstat: Fix Idle and busy PURR/SPURR

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Saket Kumar Bhaskar

<skb99@linux.ibm.com>
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May 21, 2024, 12:13:06 PMMay 21
to powerpc-utils-devel@googlegroups.com, naveen.n.rao@linux.ibm.com, srikar@linux.ibm.com, tyreld@linux.ibm.com, Saket Kumar Bhaskar
Idle and busy PURR/SPURR values are not adding upto 100% in case of
dedicated-donate and shared partitions, with the present formula.
Because of this, users might get a false impression of resource
utilisation. This is expected because a core can be in either
idle or busy state out of total of 100(core's shared resource can
either be consumed or be left idle). When lpar is in dedicated-donate
or shared,the purr values are not being counted when the CPU is ceded.
The idle_purr is calculated by taking snapshots of purr values at
every idle entry and idle exit. So, when a CPU is ceded, the calculation
for idle_purr will be wrong as purr is not being counted.

Before Change:
|-----------------------------------------------------------------|
| Dedicated-donate (8 cores) : |
|----------------------|---------------------|--------------------|
| | Actual | Normalized |
| Stress-ng threads |---------------------|--------------------|
| | %busy | %idle | %busy | %idle |
|----------------------|----------|----------|---------|----------|
| 0 threads | 0.02 | 0.11 | 0.02 | 0.12 |
|----------------------|----------|----------|---------|----------|
| 8 threads | 30.01 | 32.53 | 32.41 | 35.14 |
|----------------------|----------|----------|---------|----------|
| 16 threads | 50.30 | 24.71 | 54.33 | 26.68 |
|----------------------|----------|----------|---------|----------|
| 24 threads | 58.35 | 16.66 | 63.02 | 17.99 |
|----------------------|----------|----------|---------|----------|
| 32 threads | 65.57 | 9.44 | 70.82 | 10.19 |
|----------------------|----------|----------|---------|----------|
| 40 threads | 80.96 | 19.03 | 87.44 | 20.56 |
|----------------------|----------|----------|---------|----------|
| 48 threads | 90.57 | 9.44 | 97.82 | 10.19 |
|----------------------|----------|----------|---------|----------|
| 56 threads | 96.09 | 3.91 | 103.78 | 4.22 |
|----------------------|----------|----------|---------|----------|
| 64 threads | 100.00 | 0.00 | 103.78 | 4.22 |
|----------------------|----------|----------|---------|----------|

|-----------------------------------------------------------------|
| Shared Capped (8 VP / 4 EC) : |
|----------------------|---------------------|--------------------|
| | Actual | Normalized |
| Stress-ng threads |---------------------|--------------------|
| | %busy | %idle | %busy | %idle |
|----------------------|----------|----------|---------|----------|
| 0 threads | 0.04 | 0.18 | 0.03 | 0.19 |
|----------------------|----------|----------|---------|----------|
| 8 threads | 29.94 | 20.05 | 32.33 | 21.65 |
|----------------------|----------|----------|---------|----------|
| 16 threads | 30.26 | 19.65 | 32.36 | 21.04 |
|----------------------|----------|----------|---------|----------|
| 24 threads | 34.77 | 15.11 | 37.55 | 16.31 |
|----------------------|----------|----------|---------|----------|
| 32 threads | 39.31 | 10.57 | 42.03 | 11.33 |
|----------------------|----------|----------|---------|----------|
| 40 threads | 42.83 | 7.04 | 46.25 | 7.60 |
|----------------------|----------|----------|---------|----------|
| 48 threads | 45.56 | 4.36 | 48.72 | 4.69 |
|----------------------|----------|----------|---------|----------|
| 56 threads | 47.73 | 2.12 | 51.07 | 2.27 |
|----------------------|----------|----------|---------|----------|
| 64 threads | 49.89 | 0.00 | 53.88 | 0.00 |
|----------------------|----------|----------|---------|----------|

This commit, rather than considering delta_idle_purr for calculation of
idle ticks, takes (delta_tb - delta_purr) as ticks for which the CPUs
were in CEDE and hence idle. Following similar logic, delta_purr would
represent busy ticks when CPUs were not ceded. Since, the output was
correct for dedicated capped mode, changes has been made only for
shared and dedicated-donate mode.

After Change:
|-----------------------------------------------------------------|
| Dedicated-donate (8 cores) : |
|----------------------|---------------------|--------------------|
| | Actual | Normalized |
| Stress-ng threads |---------------------|--------------------|
| | %busy | %idle | %busy | %idle |
|----------------------|----------|----------|---------|----------|
| 0 threads | 0.09 | 99.91 | 0.09 | 99.45 |
|----------------------|----------|----------|---------|----------|
| 8 threads | 62.55 | 37.45 | 67.55 | 32.81 |
|----------------------|----------|----------|---------|----------|
| 16 threads | 75.01 | 24.99 | 81.01 | 19.35 |
|----------------------|----------|----------|---------|----------|
| 24 threads | 87.50 | 12.50 | 94.50 | 5.86 |
|----------------------|----------|----------|---------|----------|
| 32 threads | 87.51 | 12.49 | 94.51 | 5.86 |
|----------------------|----------|----------|---------|----------|
| 40 threads | 100.00 | 0.00 | 108.00 | 0.00 |
|----------------------|----------|----------|---------|----------|
| 48 threads | 100.00 | 0.00 | 108.00 | 0.00 |
|----------------------|----------|----------|---------|----------|
| 56 threads | 100.00 | 0.00 | 108.00 | 0.00 |
|----------------------|----------|----------|---------|----------|
| 64 threads | 100.00 | 0.00 | 108.00 | 0.00 |
|----------------------|----------|----------|---------|----------|

|-----------------------------------------------------------------|
| Shared Capped (8 VP / 4 EC) : |
|----------------------|---------------------|--------------------|
| | Actual | Normalized |
| Stress-ng threads |---------------------|--------------------|
| | %busy | %idle | %busy | %idle |
|----------------------|----------|----------|---------|----------|
| 0 threads | 0.18 | 99.82 | 0.19 | 99.44 |
|----------------------|----------|----------|---------|----------|
| 8 threads | 49.99 | 50.01 | 53.99 | 45.89 |
|----------------------|----------|----------|---------|----------|
| 16 threads | 49.66 | 50.34 | 53.63 | 46.71 |
|----------------------|----------|----------|---------|----------|
| 24 threads | 49.93 | 50.07 | 53.42 | 46.08 |
|----------------------|----------|----------|---------|----------|
| 32 threads | 49.92 | 50.08 | 53.41 | 46.08 |
|----------------------|----------|----------|---------|----------|
| 40 threads | 49.89 | 50.11 | 53.88 | 46.52 |
|----------------------|----------|----------|---------|----------|
| 48 threads | 49.88 | 50.12 | 53.87 | 46.41 |
|----------------------|----------|----------|---------|----------|
| 56 threads | 49.90 | 50.10 | 53.40 | 46.10 |
|----------------------|----------|----------|---------|----------|
| 64 threads | 49.90 | 50.10 | 54.39 | 45.36 |
|----------------------|----------|----------|---------|----------|

Before Change:
%busy = (delta_purr - delta_idle_purr) / delta_tb * 100
%idle = delta_idle_purr / delta_tb * 100

After Change:
%busy = delta_purr / delta_tb * 100
%idle = (delta_tb - delta_purr) / delta_tb * 100

Signed-off-by: Saket Kumar Bhaskar <sk...@linux.ibm.com>
---
src/lparstat.c | 83 ++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 73 insertions(+), 10 deletions(-)

diff --git a/src/lparstat.c b/src/lparstat.c
index d2fdb3f..e74ca17 100644
--- a/src/lparstat.c
+++ b/src/lparstat.c
@@ -491,11 +491,16 @@ void get_cpu_util_purr(struct sysentry *unused_se, char *buf)
{
double delta_tb, delta_purr, delta_idle_purr;
double physc;
+ char *descr;
+ char mode[32];

delta_tb = get_scaled_tb();
delta_purr = get_delta_value("purr");
delta_idle_purr = get_delta_value("idle_purr");

+ get_sysdata("shared_processor_mode", &descr, mode);
+ if (!strcmp(mode, "Dedicated"))
+ get_sysdata("DedDonMode", &descr, mode);
/*
* Given that these values are read from different
* sources (purr from lparcfg and idle_purr from sysfs),
@@ -505,8 +510,15 @@ void get_cpu_util_purr(struct sysentry *unused_se, char *buf)
if (delta_idle_purr > delta_purr)
delta_idle_purr = delta_purr;

- physc = (delta_purr - delta_idle_purr) / delta_tb;
- physc *= 100.00;
+ if (!strcmp(mode, "Capped")) {
+ /* For dedicated - capped mode */
+ physc = (delta_purr - delta_idle_purr) / delta_tb;
+ physc *= 100.00;
+ } else {
+ /* For shared and dedicated - donate mode */
+ physc = delta_purr / delta_tb;
+ physc *= 100.00;
+ }

sprintf(buf, "%.2f", physc);
}
@@ -515,11 +527,17 @@ void get_cpu_idle_purr(struct sysentry *unused_se, char *buf)
{
double delta_tb, delta_purr, delta_idle_purr;
double physc, idle;
+ char *descr;
+ char mode[32];

delta_tb = get_scaled_tb();
delta_purr = get_delta_value("purr");
delta_idle_purr = get_delta_value("idle_purr");

+ get_sysdata("shared_processor_mode", &descr, mode);
+ if (!strcmp(mode, "Dedicated"))
+ get_sysdata("DedDonMode", &descr, mode);
+
/*
* Given that these values are read from different
* sources (purr from lparcfg and idle_purr from sysfs),
@@ -529,9 +547,19 @@ void get_cpu_idle_purr(struct sysentry *unused_se, char *buf)
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;
+ if (delta_purr > delta_tb)
+ delta_purr = delta_tb;
+
+ if (!strcmp(mode, "Capped")) {
+ /* For dedicated - capped mode */
+ physc = (delta_purr - delta_idle_purr) / delta_tb;
+ idle = (delta_purr / delta_tb) - physc;
+ idle *= 100.00;
+ } else {
+ /* For shared and dedicated - donate mode */
+ idle = (delta_tb - delta_purr) / delta_tb;
+ idle *= 100.00;
+ }

sprintf(buf, "%.2f", idle);
}
@@ -540,13 +568,29 @@ void get_cpu_util_spurr(struct sysentry *unused_se, char *buf)
{
double delta_tb, delta_spurr, delta_idle_spurr;
double physc, rfreq;
+ char *descr;
+ char mode[32];

delta_tb = get_scaled_tb();
delta_spurr = get_delta_value("spurr");
delta_idle_spurr = get_delta_value("idle_spurr");

- physc = (delta_spurr - delta_idle_spurr) / delta_tb;
- physc *= 100.00;
+ get_sysdata("shared_processor_mode", &descr, mode);
+ if (!strcmp(mode, "Dedicated"))
+ get_sysdata("DedDonMode", &descr, mode);
+
+ if (delta_idle_spurr > delta_spurr)
+ delta_idle_spurr = delta_spurr;
+
+ if (!strcmp(mode, "Capped")) {
+ /* For dedicated - capped mode */
+ physc = (delta_spurr - delta_idle_spurr) / delta_tb;
+ physc *= 100.00;
+ } else {
+ /* For shared and dedicated - donate mode */
+ physc = delta_spurr / delta_tb;
+ physc *= 100.00;
+ }

rfreq = round_off_freq();
physc += ((physc * rfreq) / 100);
@@ -559,14 +603,33 @@ void get_cpu_idle_spurr(struct sysentry *unused_se, char *buf)
double delta_tb, delta_spurr, delta_idle_spurr;
double physc, idle;
double rfreq;
+ char *descr;
+ char mode[32];

delta_tb = get_scaled_tb();
delta_spurr = get_delta_value("spurr");
delta_idle_spurr = get_delta_value("idle_spurr");

- physc = (delta_spurr - delta_idle_spurr) / delta_tb;
- idle = (delta_spurr / delta_tb) - physc;
- idle *= 100.00;
+ get_sysdata("shared_processor_mode", &descr, mode);
+ if (!strcmp(mode, "Dedicated"))
+ get_sysdata("DedDonMode", &descr, mode);
+
+ if (delta_idle_spurr > delta_spurr)
+ delta_idle_spurr = delta_spurr;
+
+ if (delta_spurr > delta_tb)
+ delta_spurr = delta_tb;
+
+ if (!strcmp(mode, "Capped")) {
+ /* For dedicated - capped mode */
+ physc = (delta_spurr - delta_idle_spurr) / delta_tb;
+ idle = (delta_spurr / delta_tb) - physc;
+ idle *= 100.00;
+ } else {
+ /* For shared and dedicated - donate mode */
+ idle = (delta_tb - delta_spurr) / delta_tb;
+ idle *= 100.00;
+ }

rfreq = round_off_freq();
idle += ((idle * rfreq) / 100);
--
2.39.3

Srikar Dronamraju

<srikar@linux.ibm.com>
unread,
May 22, 2024, 1:31:32 AMMay 22
to Saket Kumar Bhaskar, powerpc-utils-devel@googlegroups.com, naveen.n.rao@linux.ibm.com, tyreld@linux.ibm.com
> @@ -529,9 +547,19 @@ void get_cpu_idle_purr(struct sysentry *unused_se, char *buf)
> 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;
> + if (delta_purr > delta_tb)
> + delta_purr = delta_tb;
> +
> + if (!strcmp(mode, "Capped")) {
> + /* For dedicated - capped mode */
> + physc = (delta_purr - delta_idle_purr) / delta_tb;

Are we missing setting physc in the else case.
Shouldnt physc be common for both cases?

> + idle = (delta_purr / delta_tb) - physc;
> + idle *= 100.00;
> + } else {
> + /* For shared and dedicated - donate mode */
> + idle = (delta_tb - delta_purr) / delta_tb;
> + idle *= 100.00;
> + }
>


> sprintf(buf, "%.2f", idle);
> }

Same here.

> + idle = (delta_spurr / delta_tb) - physc;
> + idle *= 100.00;
> + } else {
> + /* For shared and dedicated - donate mode */
> + idle = (delta_tb - delta_spurr) / delta_tb;
> + idle *= 100.00;
> + }
>
> rfreq = round_off_freq();
> idle += ((idle * rfreq) / 100);
> --
> 2.39.3
>

--
Thanks and Regards
Srikar Dronamraju

Naveen N. Rao

<naveen.n.rao@linux.ibm.com>
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May 23, 2024, 1:58:32 AMMay 23
to powerpc-utils-devel@googlegroups.com, Saket Kumar Bhaskar, srikar@linux.ibm.com, tyreld@linux.ibm.com
Assuming similar workloads, it is strange seeing 100% busy with >32
threads.
Is there a reason to intentionally ignore delta_idle_purr for the
calculations? Those are supposed to be purr ticks we accululated while
in idle.

- Naveen

Saket Kumar Bhaskar

<skb99@linux.ibm.com>
unread,
May 23, 2024, 5:21:36 AMMay 23
to Srikar Dronamraju, powerpc-utils-devel@googlegroups.com, naveen.n.rao@linux.ibm.com, tyreld@linux.ibm.com
On 5/22/24 11:01, Srikar Dronamraju wrote:
@@ -529,9 +547,19 @@ void get_cpu_idle_purr(struct sysentry *unused_se, char *buf)
 	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;
+	if (delta_purr > delta_tb)
+		delta_purr = delta_tb;
+
+	if (!strcmp(mode, "Capped")) {
+		/* For dedicated - capped mode */
+		physc = (delta_purr - delta_idle_purr) / delta_tb;

Are we missing setting physc in the else case.
Shouldnt physc be common for both cases?
Here, physc is not the actual physc that is shown in lparstat, rather a variable name.
Since, we don't need physc to be subtracted from anything in else condition, 
we should be fine with it. 

Thanks for review,
Saket

Srikar Dronamraju

<srikar@linux.ibm.com>
unread,
May 27, 2024, 4:45:13 AMMay 27
to Saket Kumar Bhaskar, powerpc-utils-devel@googlegroups.com, naveen.n.rao@linux.ibm.com, tyreld@linux.ibm.com
* Saket Kumar Bhaskar <sk...@linux.ibm.com> [2024-05-23 14:51:07]:

> On 5/22/24 11:01, Srikar Dronamraju wrote:
>
> > > @@ -529,9 +547,19 @@ void get_cpu_idle_purr(struct sysentry *unused_se, char *buf)
> > > 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;
> > > + if (delta_purr > delta_tb)
> > > + delta_purr = delta_tb;
> > > +
> > > + if (!strcmp(mode, "Capped")) {
> > > + /* For dedicated - capped mode */
> > > + physc = (delta_purr - delta_idle_purr) / delta_tb;
> > Are we missing setting physc in the else case.
> > Shouldnt physc be common for both cases?
>
> Here, physc is not the actual physc that is shown in lparstat, rather a variable name.
> Since, we don't need physc to be subtracted from anything in else condition,
> we should be fine with it.
>

Ok, I get it. You can ignore my comment.

Saket Kumar Bhaskar

<skb99@linux.ibm.com>
unread,
Jun 5, 2024, 5:23:47 AMJun 5
to powerpc-utils-devel@googlegroups.com, naveen.n.rao@linux.ibm.com, srikar@linux.ibm.com, tyreld@linux.ibm.com, Saket Kumar Bhaskar
Idle and busy PURR/SPURR values are not adding upto 100% in case of
dedicated-donate and shared partitions, with the present formula.
Because of this, users might get a false impression of resource
utilisation. This is expected because a core can be in either
idle or busy state out of total of 100(core's shared resource can
either be consumed or be left idle). When lpar is in dedicated-donate
or shared,the purr values are not being counted when the CPU is ceded.
The idle_purr is calculated by taking snapshots of purr values at
every idle entry and idle exit. So, when a CPU is ceded, the calculation
for idle_purr will be wrong as purr is not being counted.

Before Change:
|-----------------------------------------------------------------|
| Dedicated-donate (8 cores) : |
|----------------------|---------------------|--------------------|
| | Actual | Normalized |
| Stress-ng threads |---------------------|--------------------|
| | %busy | %idle | %busy | %idle |
|----------------------|----------|----------|---------|----------|
| 0 threads | 0.02 | 0.05 | 0.02 | 0.05 |
|----------------------|----------|----------|---------|----------|
| 8 threads | 32.64 | 17.37 | 35.25 | 18.77 |
|----------------------|----------|----------|---------|----------|
| 16 threads | 58.61 | 16.42 | 63.29 | 17.74 |
|----------------------|----------|----------|---------|----------|
| 24 threads | 78.14 | 21.86 | 84.39 | 23.61 |
|----------------------|----------|----------|---------|----------|
| 32 threads | 83.60 | 16.40 | 90.30 | 17.71 |
|----------------------|----------|----------|---------|----------|
| 40 threads | 91.90 | 6.94 | 98.31 | 7.46 |
|----------------------|----------|----------|---------|----------|
| 48 threads | 96.08 | 3.92 | 102.79 | 4.21 |
|----------------------|----------|----------|---------|----------|
| 56 threads | 98.42 | 1.57 | 105.31 | 1.69 |
|----------------------|----------|----------|---------|----------|
| 64 threads | 100.00 | 0.00 | 106.00 | 0.00 |
|----------------------|----------|----------|---------|----------|

|-----------------------------------------------------------------|
| Shared Capped (8 VP / 4 EC) : |
|----------------------|---------------------|--------------------|
| | Actual | Normalized |
| Stress-ng threads |---------------------|--------------------|
| | %busy | %idle | %busy | %idle |
|----------------------|----------|----------|---------|----------|
| 0 threads | 0.04 | 0.18 | 0.03 | 0.19 |
|----------------------|----------|----------|---------|----------|
| 8 threads | 35.90 | 14.09 | 38.77 | 15.21 |
|----------------------|----------|----------|---------|----------|
| 16 threads | 35.25 | 14.84 | 38.08 | 16.02 |
|----------------------|----------|----------|---------|----------|
| 24 threads | 40.13 | 9.73 | 42.93 | 10.43 |
|----------------------|----------|----------|---------|----------|
| 32 threads | 44.13 | 5.73 | 47.22 | 6.14 |
|----------------------|----------|----------|---------|----------|
| 40 threads | 46.47 | 3.42 | 50.18 | 3.69 |
|----------------------|----------|----------|---------|----------|
| 48 threads | 48.03 | 1.83 | 51.39 | 1.96 |
|----------------------|----------|----------|---------|----------|
| 56 threads | 49.04 | 0.86 | 52.47 | 0.93 |
|----------------------|----------|----------|---------|----------|
| 64 threads | 49.87 | 0.00 | 53.36 | 0.00 |
|----------------------|----------|----------|---------|----------|

This commit, rather than considering delta_idle_purr for calculation of
idle ticks, takes (delta_tb - delta_purr + delta_idle_purr) as total
ticks for which the CPUs were idle. Here, since delta_idle_purr will
also contain some idle ticks, thats why it is added to the formula.

Given that, in case of dedicated capped mode delta_purr will be
approximately equal to delta_idle_purr, the expression:
idle = (delta_tb - delta_purr + delta_idle_purr) / delta_tb

will be effectively:
idle = delta_idle_purr / delta_tb.

Further, no changes has been made for calculation of %busy.

After Change:

|-----------------------------------------------------------------|
| Dedicated-donate (8 cores) : |
|----------------------|---------------------|--------------------|
| | Actual | Normalized |
| Stress-ng threads |---------------------|--------------------|
| | %busy | %idle | %busy | %idle |
|----------------------|----------|----------|---------|----------|
| 0 threads | 0.02 | 99.98 | 0.02 | 100.04 |
|----------------------|----------|----------|---------|----------|
| 8 threads | 35.97 | 64.03 | 38.84 | 61.51 |
|----------------------|----------|----------|---------|----------|
| 16 threads | 58.60 | 41.40 | 63.28 | 37.08 |
|----------------------|----------|----------|---------|----------|
| 24 threads | 78.14 | 21.86 | 84.39 | 23.61 |
|----------------------|----------|----------|---------|----------|
| 32 threads | 83.60 | 16.41 | 90.29 | 17.71 |
|----------------------|----------|----------|---------|----------|
| 40 threads | 92.96 | 7.04 | 100.39 | 7.61 |
|----------------------|----------|----------|---------|----------|
| 48 threads | 96.08 | 3.92 | 103.77 | 4.24 |
|----------------------|----------|----------|---------|----------|
| 56 threads | 98.42 | 1.58 | 105.31 | 1.68 |
|----------------------|----------|----------|---------|----------|
| 64 threads | 100.00 | 0.00 | 107.00 | 0.00 |
|----------------------|----------|----------|---------|----------|

|-----------------------------------------------------------------|
| Shared Capped (8 VP / 4 EC) : |
|----------------------|---------------------|--------------------|
| | Actual | Normalized |
| Stress-ng threads |---------------------|--------------------|
| | %busy | %idle | %busy | %idle |
|----------------------|----------|----------|---------|----------|
| 0 threads | 0.03 | 99.97 | 0.19 | 99.44 |
|----------------------|----------|----------|---------|----------|
| 8 threads | 35.91 | 64.09 | 38.78 | 61.58 |
|----------------------|----------|----------|---------|----------|
| 16 threads | 36.83 | 63.17 | 39.78 | 60.55 |
|----------------------|----------|----------|---------|----------|
| 24 threads | 40.16 | 59.84 | 43.37 | 56.95 |
|----------------------|----------|----------|---------|----------|
| 32 threads | 44.47 | 55.53 | 48.02 | 52.38 |
|----------------------|----------|----------|---------|----------|
| 40 threads | 46.55 | 53.45 | 50.27 | 50.04 |
|----------------------|----------|----------|---------|----------|
| 48 threads | 48.13 | 51.87 | 52.48 | 47.82 |
|----------------------|----------|----------|---------|----------|
| 56 threads | 49.01 | 50.99 | 52.93 | 47.41 |
|----------------------|----------|----------|---------|----------|
| 64 threads | 49.90 | 50.10 | 53.40 | 46.19 |
|----------------------|----------|----------|---------|----------|

Before Change:
%idle = delta_idle_purr / delta_tb * 100

After Change:
%idle = (delta_tb - delta_purr + delta_idle_purr) / delta_tb * 100

Signed-off-by: Saket Kumar Bhaskar <sk...@linux.ibm.com>
---

v1 -> v2:
- Ticks accounted in delta_idle_purr were missed for busy and idle
calculation, as pointed out by Naveen.
- Because of this we were also seeing high busy values for lesser
number of threads.
- Generic formula for %idle calculation in case of dedicated and shared
lpar.

v1: https://groups.google.com/g/powerpc-utils-devel/c/IZs0Norg8nc


src/lparstat.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/lparstat.c b/src/lparstat.c
index d2fdb3f..0a81329 100644
--- a/src/lparstat.c
+++ b/src/lparstat.c
@@ -514,24 +514,26 @@ void get_cpu_util_purr(struct sysentry *unused_se, char *buf)
void get_cpu_idle_purr(struct sysentry *unused_se, char *buf)
{
double delta_tb, delta_purr, delta_idle_purr;
- double physc, idle;
+ double idle;

delta_tb = get_scaled_tb();
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;
+ if (delta_purr > delta_tb)
+ delta_purr = delta_tb;
+
+ idle = (delta_tb - delta_purr + delta_idle_purr) / delta_tb;
idle *= 100.00;

sprintf(buf, "%.2f", idle);
}
@@ -539,17 +541,20 @@ void get_cpu_idle_purr(struct sysentry *unused_se, char *buf)
void get_cpu_util_spurr(struct sysentry *unused_se, char *buf)
{
double delta_tb, delta_spurr, delta_idle_spurr;
double physc, rfreq;

delta_tb = get_scaled_tb();
delta_spurr = get_delta_value("spurr");
delta_idle_spurr = get_delta_value("idle_spurr");

+ if (delta_idle_spurr > delta_spurr)
+ delta_idle_spurr = delta_spurr;
+
physc = (delta_spurr - delta_idle_spurr) / delta_tb;
physc *= 100.00;

rfreq = round_off_freq();
physc += ((physc * rfreq) / 100);

sprintf(buf, "%.2f", physc);
}
@@ -557,19 +562,24 @@ void get_cpu_util_spurr(struct sysentry *unused_se, char *buf)
void get_cpu_idle_spurr(struct sysentry *unused_se, char *buf)
{
double delta_tb, delta_spurr, delta_idle_spurr;
- double physc, idle;
+ double idle;
double rfreq;

delta_tb = get_scaled_tb();
delta_spurr = get_delta_value("spurr");
delta_idle_spurr = get_delta_value("idle_spurr");

- physc = (delta_spurr - delta_idle_spurr) / delta_tb;
- idle = (delta_spurr / delta_tb) - physc;
+ if (delta_idle_spurr > delta_spurr)
+ delta_idle_spurr = delta_spurr;
+
+ if (delta_spurr > delta_tb)
+ delta_spurr = delta_tb;
+
+ idle = (delta_tb - delta_spurr + delta_idle_spurr) / delta_tb;
idle *= 100.00;

rfreq = round_off_freq();
idle += ((idle * rfreq) / 100);

sprintf(buf, "%.2f", idle);
}
--
2.39.3

Srikar Dronamraju

<srikar@linux.ibm.com>
unread,
Jun 6, 2024, 2:23:00 AMJun 6
to Saket Kumar Bhaskar, powerpc-utils-devel@googlegroups.com, naveen.n.rao@linux.ibm.com, tyreld@linux.ibm.com
* Saket Kumar Bhaskar <sk...@linux.ibm.com> [2024-06-05 14:52:27]:

> Idle and busy PURR/SPURR values are not adding upto 100% in case of
> dedicated-donate and shared partitions, with the present formula.
> Because of this, users might get a false impression of resource
> utilisation. This is expected because a core can be in either
> idle or busy state out of total of 100(core's shared resource can
> either be consumed or be left idle). When lpar is in dedicated-donate
> or shared,the purr values are not being counted when the CPU is ceded.
> The idle_purr is calculated by taking snapshots of purr values at
> every idle entry and idle exit. So, when a CPU is ceded, the calculation
> for idle_purr will be wrong as purr is not being counted.
>

Looks good to me.

Reviewed-by: Srikar Dronamraju <sri...@linux.ibm.com>

Saket Kumar Bhaskar

<skb99@linux.ibm.com>
unread,
Jun 10, 2024, 1:03:14 AM (11 days ago) Jun 10
to Srikar Dronamraju, powerpc-utils-devel@googlegroups.com, naveen.n.rao@linux.ibm.com, tyreld@linux.ibm.com
Thanks for reviewing, Srikar.

Best Regards,
Saket Kumar Bhaskar

Naveen N. Rao

<naveen.n.rao@linux.ibm.com>
unread,
Jun 12, 2024, 1:30:41 AM (9 days ago) Jun 12
to powerpc-utils-devel@googlegroups.com, Saket Kumar Bhaskar, srikar@linux.ibm.com, tyreld@linux.ibm.com
The numbers look good now.
Two minor concerns:
- Do you often see delta_purr to be larger than delta_tb? Is it a
rounding error, or is the difference much bigger?
- You also generalize the calculation here, and is no longer specific to
shared/ded-donate. Not sure if this can hide bugs in our purr
accounting, et al.

Hopefully not big issues, but would be good to get confirmation on the
above.


- Naveen

Saket Kumar Bhaskar

<skb99@linux.ibm.com>
unread,
Jun 19, 2024, 1:35:31 AM (2 days ago) Jun 19
to Naveen N. Rao, powerpc-utils-devel@googlegroups.com, srikar@linux.ibm.com, tyreld@linux.ibm.com
I have seen for dedicated-donate, delta_purr > delta_tb and delta_spurr>delta_tb.

I removed the if condition (if (delta_purr > delta_tb)), and dumped the delta
values on a 64 CPUs system:

1. For 64 threads:

#./lparstat -E 1 30

System Configuration
type=Dedicated mode=Donating smt=8 lcpu=8 mem=102544256 kB cpus=0 ent=8.00

---Actual--- -Normalized-
%busy %idle Frequency %busy %idle
------ ------ ------------- ------ ------
delta_purr 4194065168.000000 delta_tb 4193853440.000000 delta_idle_purr 0.000000 delta_spurr 4513401456.000000 delta_tb 4193853440.000000 delta_idle_spurr 0.000000 100.01 -0.01 3.87GHz[108%] 108.01 -7.65
delta_purr 4115058032.000000 delta_tb 4115066880.000000 delta_idle_purr 0.000000 delta_spurr 4428474080.000000 delta_tb 4115066880.000000 delta_idle_spurr 0.000000 100.00 0.00 3.87GHz[108%] 108.00 -7.64
delta_purr 4114827136.000000 delta_tb 4114767872.000000 delta_idle_purr 0.000000 delta_spurr 4430429340.000000 delta_tb 4114767872.000000 delta_idle_spurr 0.000000 100.00 -0.00 3.88GHz[108%] 108.00 -7.69
delta_purr 4117258032.000000 delta_tb 4117172224.000000 delta_idle_purr 0.000000 delta_spurr 4430827912.000000 delta_tb 4117172224.000000 delta_idle_spurr 0.000000 100.00 -0.00 3.87GHz[108%] 108.00 -7.65
delta_purr 4116939616.000000 delta_tb 4116955136.000000 delta_idle_purr 0.000000 delta_spurr 4429904076.000000 delta_tb 4116955136.000000 delta_idle_spurr 0.000000 100.00 0.00 3.87GHz[108%] 108.00 -7.63

2. For 56 threads:

#./lparstat -E 1 30

System Configuration
type=Dedicated mode=Donating smt=8 lcpu=8 mem=102544256 kB cpus=0 ent=8.00

---Actual--- -Normalized-
%busy %idle Frequency %busy %idle
------ ------ ------------- ------ ------
delta_purr 4124239336.000000 delta_tb 4124053504.000000 delta_idle_purr 65320864.000000 delta_spurr 4438340384.000000 delta_tb 4124053504.000000 delta_idle_spurr 70298488.000000 98.42 1.58 3.87GHz[108%] 106.29 -5.94
delta_purr 4115783736.000000 delta_tb 4115742720.000000 delta_idle_purr 64844040.000000 delta_spurr 4430295260.000000 delta_tb 4115742720.000000 delta_idle_spurr 69784284.000000 98.43 1.57 3.88GHz[108%] 106.30 -5.97
delta_purr 4116809568.000000 delta_tb 4117000192.000000 delta_idle_purr 64362656.000000 delta_spurr 4429448892.000000 delta_tb 4117000192.000000 delta_idle_spurr 69267872.000000 98.43 1.57 3.87GHz[108%] 106.31 -5.93
delta_purr 4115649744.000000 delta_tb 4115554304.000000 delta_idle_purr 64738312.000000 delta_spurr 4429501792.000000 delta_tb 4115554304.000000 delta_idle_spurr 69671320.000000 98.43 1.57 3.87GHz[108%] 106.30 -5.96
delta_purr 4115961312.000000 delta_tb 4115902464.000000 delta_idle_purr 64828552.000000 delta_spurr 4429060776.000000 delta_tb 4115902464.000000 delta_idle_spurr 69768592.000000 98.43 1.57 3.87GHz[108%] 106.30 -5.93

We can see negative values for %idle purr/spurr, because delta_(s)purr > delta_tb.

> - You also generalize the calculation here, and is no longer specific to
> shared/ded-donate. Not sure if this can hide bugs in our purr accounting,
> et al.
>
Earlier, too we had generic formula. IMO, I dont see any specific reason for
different formulas for dedicated-donate and shared as of now.

> Hopefully not big issues, but would be good to get confirmation on the
> above.
>
>
> - Naveen
>
Thanks,
Saket Kumar Bhaskar
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