[PATCH] ppc64_cpu/info: fix bad report when non continuous CPU ids

[Laurent Dufour]

When CPU ids are not continuous, let say that the kernel didn't reuse a set
of CPU ids already used on a different nodes, the output of ppc64_cpu
--info is not correct.

For instance, in the example below the CPU id 48 to 55 haven't been reused
by the kernel when a CPU has been added after a LPM operation.
Note that the system is running in SMT=4.

The numactl -H command is providing the correct set of CPU:
ltczep3-lp4:~ # numactl -H
available: 2 nodes (0-1)
node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 64 65 66 67 68 69 70 71
node 0 size: 7177 MB
node 0 free: 4235 MB
node 1 cpus: 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
node 1 size: 24508 MB
node 1 free: 23539 MB
node distances:
node 0 1
0: 10 40
1: 40 10

But ppc64_cpu --info is reporting the CPUs 48 to 55 offlined while not
reporting at all the CPU 65 to 71:
ltczep3-lp4:~ # ppc64_cpu --info
Core 0: 0* 1* 2* 3* 4* 5* 6* 7*
Core 1: 8* 9* 10* 11* 12* 13* 14* 15*
Core 2: 16* 17* 18* 19* 20* 21* 22* 23*
Core 3: 24* 25* 26* 27* 28* 29* 30* 31*
Core 4: 32* 33* 34* 35* 36* 37* 38* 39*
Core 5: 40* 41* 42* 43* 44* 45* 46* 47*
Core 6: 48 49 50 51 52 53 54 55

This is because it is considering that the CPU id are continuous which is
not the case here.

To prevent that, when looking for a core, it is now first checking that the
physical_id of the first thread in that core is defined (not -1). If that
the case this means that CPU/core is present.

With that patch applied, ppc64_cpu --info is reporting:
ltczep3-lp4:~ # pc64_cpu --info
Core 0: 0* 1* 2* 3* 4 5 6 7
Core 1: 8* 9* 10* 11* 12 13 14 15
Core 2: 16* 17* 18* 19* 20 21 22 23
Core 3: 24* 25* 26* 27* 28 29 30 31
Core 4: 32* 33* 34* 35* 36 37 38 39
Core 5: 40* 41* 42* 43* 44 45 46 47
Core 6: 64* 65* 66* 67* 68 69 70 71

Signed-off-by: Laurent Dufour <ldu...@linux.ibm.com>
---
src/common/cpu_info_helpers.c | 14 ++++++++++++++
src/common/cpu_info_helpers.h | 1 +
src/ppc64_cpu.c | 25 +++++++++++++++++--------
3 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/src/common/cpu_info_helpers.c b/src/common/cpu_info_helpers.c
index c05d96d5b3cc..8c57db8b9550 100644
--- a/src/common/cpu_info_helpers.c
+++ b/src/common/cpu_info_helpers.c
@@ -83,6 +83,20 @@ int __sysattr_is_writeable(char *attribute, int threads_in_system)
return test_sysattr(attribute, W_OK, threads_in_system);
}

+int cpu_physical_id(int thread)
+{
+ char path[SYSFS_PATH_MAX];
+ int rc, physical_id;
+
+ sprintf(path, SYSFS_CPUDIR"/physical_id", thread);
+ rc = get_attribute(path, "%d", &physical_id);
+
+ /* This attribute does not exist in kernels without hotplug enabled */
+ if (rc && errno == ENOENT)
+ return -1;
+ return physical_id;
+}
+
int cpu_online(int thread)
{
char path[SYSFS_PATH_MAX];
diff --git a/src/common/cpu_info_helpers.h b/src/common/cpu_info_helpers.h
index 8f09d7911d53..c063fff9a4d4 100644
--- a/src/common/cpu_info_helpers.h
+++ b/src/common/cpu_info_helpers.h
@@ -32,6 +32,7 @@

extern int __sysattr_is_readable(char *attribute, int threads_in_system);
extern int __sysattr_is_writeable(char *attribute, int threads_in_system);
+extern int cpu_physical_id(int thread);
extern int cpu_online(int thread);
extern int is_subcore_capable(void);
extern int num_subcores(void);
diff --git a/src/ppc64_cpu.c b/src/ppc64_cpu.c
index 653b54402236..87fbbe3e412b 100644
--- a/src/ppc64_cpu.c
+++ b/src/ppc64_cpu.c
@@ -1269,31 +1269,40 @@ static int do_cores_on(char *state)
return 0;
}

+static bool core_is_online(int core)
+{
+ return cpu_physical_id(core * threads_per_cpu) != -1;
+}
+
static int do_info(void)
{
int i, j, thread_num;
char online;
- int subcores = 0;
+ int core, subcores = 0;

if (is_subcore_capable())
subcores = num_subcores();

- for (i = 0; i < cpus_in_system; i++) {
+ for (i = 0, core = 0; core < cpus_in_system; i++) {
+
+ if (!core_is_online(i))
+ continue;

if (subcores > 1) {
- if (i % subcores == 0)
- printf("Core %3d:\n", i/subcores);
- printf(" Subcore %3d: ", i);
+ if (core % subcores == 0)
+ printf("Core %3d:\n", core/subcores);
+ printf(" Subcore %3d: ", core);
} else {
- printf("Core %3d: ", i);
+ printf("Core %3d: ", core);
}

- for (j = 0; j < threads_per_cpu; j++) {
- thread_num = i*threads_per_cpu + j;
+ thread_num = i * threads_per_cpu;
+ for (j = 0; j < threads_per_cpu; j++, thread_num++) {
online = cpu_online(thread_num) ? '*' : ' ';
printf("%4d%c ", thread_num, online);
}
printf("\n");
+ core++;
}
return 0;
}
--
2.41.0

[Nathan Lynch]

Reviewed-by: Nathan Lynch <nat...@linux.ibm.com>

[Tyrel Datwyler]

Patch applied to powerpc-utils/next branch.

https://github.com/ibm-power-utilities/powerpc-utils/commit/f1a8ed892e18b83cb0483e8f8f8cbc512fa8510c

Thanks,
-Tyrel