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

From: Huang Ying
Date: Wed Sep 20 2023 - 02:19:55 EST


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