From: "Gautham R. Shenoy" <e...@linux.vnet.ibm.com> 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 00000001 00000002 00000004 00000000 00000002 00000004 00000006 00000001 00000003 00000005 00000007 00000002 00000002 00000004 00000000 00000002 00000004 00000006 00000001 00000003 00000005 00000007 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:000000,000000ff /sys/devices/system/cpu/cpu1/cache/index2/shared_cpu_list:0-7 /sys/devices/system/cpu/cpu1/cache/index2/shared_cpu_map:000000,000000ff 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:000000,00000055 /sys/devices/system/cpu/cpu1/cache/index2/shared_cpu_list:1,3,5,7 /sys/devices/system/cpu/cpu1/cache/index2/shared_cpu_map:000000,000000aa Signed-off-by: Gautham R. Shenoy <e...@linux.vnet.ibm.com> --- arch/powerpc/kernel/cacheinfo.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/powerpc/kernel/cacheinfo.c b/arch/powerpc/kernel/cacheinfo.c index 65ab9fc..1cc8f37 100644 --- a/arch/powerpc/kernel/cacheinfo.c +++ b/arch/powerpc/kernel/cacheinfo.c @@ -651,15 +651,22 @@ static unsigned int index_dir_to_cpu(struct cache_index_dir *index) return dev->id; } +extern bool thread_group_shares_l2; /* * 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(). */ static const struct cpumask *get_big_core_shared_cpu_map(int cpu, struct cache *cache) { 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; } -- 1.9.4