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lparstat: Fix Idle and busy PURR/SPURR
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lparstat -E gives %busy and %idle for actual(PURR based) and normalized
(SPURR based).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.
Since, the output was correct for dedicated capped mode, changes has
been made only for shared and dedicated-donate mode.
Further, no changes has been made for calculation of %busy.

Similar changes has been done for SPURR.

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 <[email protected]>
Signed-off-by: Tyrel Datwyler <[email protected]>
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@tyreld
Saket Kumar Bhaskar authored and tyreld committed Jul 26, 2024
1 parent 5db2df5 commit 2af8c0b
Showing 1 changed file with 42 additions and 7 deletions.
49 changes: 42 additions & 7 deletions src/lparstat.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -515,11 +515,17 @@ 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),
Expand All @@ -528,10 +534,23 @@ 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;
/*
* Round down delta_purr to delta_tb if delta_tb - delta_purr
* error is under -1%.
*/
if (((delta_tb - delta_purr + delta_idle_purr) / delta_tb * 100) > -1 && ((delta_tb - delta_purr + delta_idle_purr) / delta_tb * 100) < 0)
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_idle_purr) / delta_tb;
idle *= 100.00;
}

sprintf(buf, "%.2f", idle);
}
Expand Down Expand Up @@ -559,14 +578,30 @@ 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_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_idle_spurr) / delta_tb;
idle *= 100.00;
}

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

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