From: "Gautham R. Shenoy"
On POWER platforms where only some groups of threads within a core
share the L2-cache (indicated by the ibm,thread-groups device-tree
property), we currently print the incorrect shared_cpu_map/list for
L2-cache in the sysfs.
This patch reports the correct shared_cpu_map/list on such platforms.
Example:
On a platform with "ibm,thread-groups" set to
0001 0002 0004
0002 0004 0006 0001
0003 0005 0007 0002
0002 0004 0002
0004 0006 0001 0003
0005 0007
This indicates that threads {0,2,4,6} in the core share the L2-cache
and threads {1,3,5,7} in the core share the L2 cache.
However, without the patch, the shared_cpu_map/list for L2 for CPUs 0,
1 is reported in the sysfs as follows:
/sys/devices/system/cpu/cpu0/cache/index2/shared_cpu_list:0-7
/sys/devices/system/cpu/cpu0/cache/index2/shared_cpu_map:00,00ff
/sys/devices/system/cpu/cpu1/cache/index2/shared_cpu_list:0-7
/sys/devices/system/cpu/cpu1/cache/index2/shared_cpu_map:00,00ff
With the patch, the shared_cpu_map/list for L2 cache for CPUs 0, 1 is
correctly reported as follows:
/sys/devices/system/cpu/cpu0/cache/index2/shared_cpu_list:0,2,4,6
/sys/devices/system/cpu/cpu0/cache/index2/shared_cpu_map:00,0055
/sys/devices/system/cpu/cpu1/cache/index2/shared_cpu_list:1,3,5,7
/sys/devices/system/cpu/cpu1/cache/index2/shared_cpu_map:00,00aa
This patch also defines cpu_l2_cache_mask() for !CONFIG_SMP case.
Signed-off-by: Gautham R. Shenoy
---
arch/powerpc/include/asm/smp.h | 4
arch/powerpc/kernel/cacheinfo.c | 30 --
2 files changed, 24 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index 035459c..c4e2d53 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -201,6 +201,10 @@ static inline const struct cpumask *cpu_smallcore_mask(int
cpu)
return cpumask_of(cpu);
}
+static inline const struct cpumask *cpu_l2_cache_mask(int cpu)
+{
+ return cpumask_of(cpu);
+}
#endif /* CONFIG_SMP */
#ifdef CONFIG_PPC64
diff --git a/arch/powerpc/kernel/cacheinfo.c b/arch/powerpc/kernel/cacheinfo.c
index 65ab9fc..6f903e9a 100644
--- a/arch/powerpc/kernel/cacheinfo.c
+++ b/arch/powerpc/kernel/cacheinfo.c
@@ -655,11 +655,27 @@ static unsigned int index_dir_to_cpu(struct
cache_index_dir *index)
* On big-core systems, each core has two groups of CPUs each of which
* has its own L1-cache. The thread-siblings which share l1-cache with
* @cpu can be obtained via cpu_smallcore_mask().
+ *
+ * On some big-core systems, the L2 cache is shared only between some
+ * groups of siblings. This is already parsed and encoded in
+ * cpu_l2_cache_mask().
+ *
+ * TODO: cache_lookup_or_instantiate() needs to be made aware of the
+ * "ibm,thread-groups" property so that cache->shared_cpu_map
+ * reflects the correct siblings on platforms that have this
+ * device-tree property. This helper function is only a stop-gap
+ * solution so that we report the correct siblings to the
+ * userspace via sysfs.
*/
-static const struct cpumask *get_big_core_shared_cpu_map(int cpu, struct cache
*cache)
+static const struct cpumask *get_shared_cpu_map(struct cache_index_dir *index,
struct cache *cache)
{
- if (cache->level == 1)
- return cpu_smallcore_mask(cpu);
+ if (has_big_cores) {
+ int cpu = index_dir_to_cpu(index);
+ if (cache->level == 1)
+ return cpu_smallcore_mask(cpu);
+ if (cache->level == 2 && thread_group_shares_l2)
+ return cpu_l2_cache_mask(cpu);
+ }
return &cache->shared_cpu_map;
}
@@ -670,17 +686,11 @@ static const struct cpumask
*get_big_core_shared_cpu_map(int cpu, struct cache *
struct cache_index_dir *index;
struct cache *cache;
const struct cpumask *mask;
- int cpu;
index = kobj_to_cache_index_dir(k);
cache = index->cache;
- if (has_big_cores) {
- cpu = index_dir_to_cpu(index);
- mask = get_big_core_shared_cpu_map(cpu, cache);
- } else {
- mask = &cache->shared_cpu_map;
- }
+ mask = get_shared_cpu_map(index, cache);
return cpumap_print_to_pagebuf(list, buf, mask);
}
--
1.9.4
