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authorGautham R. Shenoy <ego@linux.vnet.ibm.com>2020-12-10 11:38:59 +0100
committerMichael Ellerman <mpe@ellerman.id.au>2020-12-10 14:10:25 +0100
commit0be47634db0baa9e91c7e635e7e73355d6a5cf43 (patch)
treec4d119a67f2fa32d44f2ae4e661d7d92a6f20bf9 /arch/powerpc/kernel/cacheinfo.c
parentpowerpc/smp: Add support detecting thread-groups sharing L2 cache (diff)
downloadlinux-0be47634db0baa9e91c7e635e7e73355d6a5cf43.tar.xz
linux-0be47634db0baa9e91c7e635e7e73355d6a5cf43.zip
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 <ego@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1607596739-32439-6-git-send-email-ego@linux.vnet.ibm.com
Diffstat (limited to 'arch/powerpc/kernel/cacheinfo.c')
-rw-r--r--arch/powerpc/kernel/cacheinfo.c30
1 files changed, 20 insertions, 10 deletions
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);
}