lparstat: app: Use pic value at boot for accurate boot time reporting

When there are no options specified for lparstat, it is expected to
give reports since LPAR(Logical Partition) boot. APP(Available Physical
Processors) is an indicator for available cores in an Shared Processor
LPAR(SPLPAR). APP is derived using pool_idle_time which is obtained
using H_PIC call.

The interval based reports show correct APP value while since boot
report shows very high APP values. This happens because in that case APP
is obtained by dividing pool idle time by LPAR uptime. Since pool idle
time is reported by the PowerVM hypervisor since its boot, it need not
align with LPAR boot.

To fix that use the boot pool idle time added newly in the lparcfg as
below.

APP = (pool idle time - boot pool idle time) / (uptime * timebase)

*This depends on "powerpc/pseries: Add pool idle time at LPAR boot" be
merged into kernel*

Results:  (Observe APP values)
========================================================================
lparstat
System Configuration
type=Shared mode=Uncapped smt=8 lcpu=12 mem=15573440 kB cpus=37 ent=12.00

reboot
stress-ng --cpu=$(nproc) -t 600
sleep 600
So in this case app is expected to close to 37-6=31.

====== 6.9-rc1 and lparstat 1.3.10  =============
%user  %sys %wait    %idle    physc %entc lbusy   app  vcsw phint
----- ----- -----    -----    ----- ----- ----- ----- ----- -----
47.48  0.01  0.00    52.51     0.00  0.00 47.49 69099.72 541547    21

=== With this patch and this patch to do the above equation ===
%user  %sys %wait    %idle    physc %entc lbusy   app  vcsw phint
----- ----- -----    -----    ----- ----- ----- ----- ----- -----
47.48  0.01  0.00    52.51     5.73 47.75 47.49 31.21 541753    21

Signed-off-by: Shrikanth Hegde <[email protected]>
Signed-off-by: Tyrel Datwyler <[email protected]>

src/lparstat.c

@@ -460,7 +460,8 @@ void get_cpu_app(struct sysentry *unused_se, char *buf)
 	se = get_sysentry("pool_idle_time");
 	new_app = strtoll(se->value, NULL, 0);
 	if (se->old_value[0] == '\0') {
-		old_app = 0;
+		se = get_sysentry("boot_pool_idle_time");
+		old_app = strtoll(se->value, NULL, 0);
 	} else {
 		old_app = strtoll(se->old_value, NULL, 0);
 	}

src/lparstat.h

@@ -124,6 +124,8 @@ struct sysentry system_data[] = {
 	 .get = &get_percent_entry},
 	{.name = "pool_idle_time",
 	 .descr = "Shared Processor Pool Idle Time"},
+	{.name = "boot_pool_idle_time",
+	 .descr = "Shared Processor Pool Idle Time"},
 	{.name = "pool_num_procs",
 	 .descr = "Shared Processor Pool Processors"},
 	{.name = "unallocated_capacity_weight",