From 0be47634db0baa9e91c7e635e7e73355d6a5cf43 Mon Sep 17 00:00:00 2001 From: "Gautham R. Shenoy" Date: Thu, 10 Dec 2020 16:08:59 +0530 Subject: powerpc/cacheinfo: Print correct cache-sibling map/list for L2 cache 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 This patch also defines cpu_l2_cache_mask() for !CONFIG_SMP case. Signed-off-by: Gautham R. Shenoy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/1607596739-32439-6-git-send-email-ego@linux.vnet.ibm.com --- arch/powerpc/kernel/cacheinfo.c | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-) (limited to 'arch/powerpc/kernel') diff --git a/arch/powerpc/kernel/cacheinfo.c b/arch/powerpc/kernel/cacheinfo.c index 65ab9fcebd31..6f903e9aa20b 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 @@ show_shared_cpumap(struct kobject *k, struct kobj_attribute *attr, char *buf, bo 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); } -- cgit v1.2.3