[PATCH 02/10] cacheinfo: calculate per-CPU data cache size

[Huang Ying]

Per-CPU data cache size is useful information.  For example, it can be
used to determine per-CPU cache size.  So, in this patch, the data
cache size for each CPU is calculated via data_cache_size /
shared_cpu_weight.

A brute-force algorithm to iterate all online CPUs is used to avoid
to allocate an extra cpumask, especially in offline callback.

Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Sudeep Holla <sudeep.holla@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Johannes Weiner <jweiner@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
---
 drivers/base/cacheinfo.c  | 42 ++++++++++++++++++++++++++++++++++++++-
 include/linux/cacheinfo.h |  1 +
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index cbae8be1fe52..3e8951a3fbab 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -898,6 +898,41 @@ static int cache_add_dev(unsigned int cpu)
 	return rc;
 }
 
+static void update_data_cache_size_cpu(unsigned int cpu)
+{
+	struct cpu_cacheinfo *ci;
+	struct cacheinfo *leaf;
+	unsigned int i, nr_shared;
+	unsigned int size_data = 0;
+
+	if (!per_cpu_cacheinfo(cpu))
+		return;
+
+	ci = ci_cacheinfo(cpu);
+	for (i = 0; i < cache_leaves(cpu); i++) {
+		leaf = per_cpu_cacheinfo_idx(cpu, i);
+		if (leaf->type != CACHE_TYPE_DATA &&
+		    leaf->type != CACHE_TYPE_UNIFIED)
+			continue;
+		nr_shared = cpumask_weight(&leaf->shared_cpu_map);
+		if (!nr_shared)
+			continue;
+		size_data += leaf->size / nr_shared;
+	}
+	ci->size_data = size_data;
+}
+
+static void update_data_cache_size(bool cpu_online, unsigned int cpu)
+{
+	unsigned int icpu;
+
+	for_each_online_cpu(icpu) {
+		if (!cpu_online && icpu == cpu)
+			continue;
+		update_data_cache_size_cpu(icpu);
+	}
+}
+
 static int cacheinfo_cpu_online(unsigned int cpu)
 {
 	int rc = detect_cache_attributes(cpu);
@@ -906,7 +941,11 @@ static int cacheinfo_cpu_online(unsigned int cpu)
 		return rc;
 	rc = cache_add_dev(cpu);
 	if (rc)
-		free_cache_attributes(cpu);
+		goto err;
+	update_data_cache_size(true, cpu);
+	return 0;
+err:
+	free_cache_attributes(cpu);
 	return rc;
 }
 
@@ -916,6 +955,7 @@ static int cacheinfo_cpu_pre_down(unsigned int cpu)
 		cpu_cache_sysfs_exit(cpu);
 
 	free_cache_attributes(cpu);
+	update_data_cache_size(false, cpu);
 	return 0;
 }
 
diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
index a5cfd44fab45..4e7ccfa0c36d 100644
--- a/include/linux/cacheinfo.h
+++ b/include/linux/cacheinfo.h
@@ -73,6 +73,7 @@ struct cacheinfo {
 
 struct cpu_cacheinfo {
 	struct cacheinfo *info_list;
+	unsigned int size_data;
 	unsigned int num_levels;
 	unsigned int num_leaves;
 	bool cpu_map_populated;
-- 
2.39.2