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linux其它邮件列表：Majordomo Lists at VGER.KERNEL.ORG
有趣的邮件记录:
一. 人生三问
What are you trying to do?
What problem are you solving?
Why are you doing any of this?
On Fri, Apr 22, 2022 at 04:51:25AM -0700, Qing Wang wrote:
From: Wang Qing <wangqing@>
When ACPI is not enabled, we can get cache topolopy from DT like:
* cpu0: cpu@000 {
* next-level-cache = <&L2_1>;
* L2_1: l2-cache {
* compatible = "cache";
* next-level-cache = <&L3_1>;
* };
* L3_1: l3-cache {
* compatible = "cache";
* };
* };
*
* cpu1: cpu@001 {
* next-level-cache = <&L2_1>;
* };
* ...
* };
cache_topology[] hold the pointer describing by "next-level-cache",
which can describe the cache topology of every level.
MAX_CACHE_LEVEL is strictly corresponding to the cache level from L2.
I have no idea what this changelog means at all.
What are you trying to do? What problem are you solving? Why are you
doing any of this?
完整邮件:
On Fri, Apr 22, 2022 at 04:51:25AM -0700, Qing Wang wrote:
From: Wang Qing <wangqing@>
When ACPI is not enabled, we can get cache topolopy from DT like:
* cpu0: cpu@000 {
* next-level-cache = <&L2_1>;
* L2_1: l2-cache {
* compatible = "cache";
* next-level-cache = <&L3_1>;
* };
* L3_1: l3-cache {
* compatible = "cache";
* };
* };
*
* cpu1: cpu@001 {
* next-level-cache = <&L2_1>;
* };
* ...
* };
cache_topology[] hold the pointer describing by "next-level-cache",
which can describe the cache topology of every level.
MAX_CACHE_LEVEL is strictly corresponding to the cache level from L2.
I have no idea what this changelog means at all.
What are you trying to do? What problem are you solving? Why are you
doing any of this?
V2:
make function name more sense
As per the documentation this goes below the --- line, right?
Signed-off-by: Wang Qing <wangqing@>
---
drivers/base/arch_topology.c | 47 ++++++++++++++++++++++++++++++++++-
include/linux/arch_topology.h | 3 +++
2 files changed, 49 insertions(+), 1 deletion(-)
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 1d6636ebaac5..46e84ce2ec0c 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -480,8 +480,10 @@ static int __init get_cpu_for_node(struct device_node *node)
return -1;
cpu = of_cpu_node_to_id(cpu_node);
- if (cpu >= 0)
+ if (cpu >= 0) {
topology_parse_cpu_capacity(cpu_node, cpu);
+ topology_parse_cpu_caches(cpu_node, cpu);
+ }
else
pr_info("CPU node for %pOF exist but the possible cpu range is :%*pbl\n",
cpu_node, cpumask_pr_args(cpu_possible_mask));
@@ -647,6 +649,49 @@ static int __init parse_dt_topology(void)
}
#endif
+/*
+ * cpu cache topology table
+ */
+#define MAX_CACHE_LEVEL 7
+static struct device_node *cache_topology[NR_CPUS][MAX_CACHE_LEVEL];
So for a normal big system of 4k cpus * 7 levels, that's a lot of
memory? are you sure?
How big of a box did you test this on?
+
+void topology_parse_cpu_caches(struct device_node *cpu_node, int cpu)
+{
+ struct device_node *node_cache = cpu_node;
+ int level = 0;
+
+ while (level < MAX_CACHE_LEVEL) {
+ node_cache = of_parse_phandle(node_cache, "next-level-cache", 0);
+ if (!node_cache)
+ break;
+
+ cache_topology[cpu][level++] = node_cache;
+ }
No locking anywhere? What could go wrong :(
+}
+
+/*
+ * find the largest subset of the shared cache in the range of cpu_mask
+ */
+void find_subset_of_share_cache(const struct cpumask *cpu_mask, int cpu,
+ struct cpumask *sc_mask)
Again, horrid global function name.
And no kernel documentation for how this works?
+{
+ int cache_level, cpu_id;
+
+ for (cache_level = MAX_CACHE_LEVEL - 1; cache_level >= 0; cache_level--) {
+ if (!cache_topology[cpu][cache_level])
+ continue;
No locking???
+
+ cpumask_clear(sc_mask);
+ for (cpu_id = 0; cpu_id < NR_CPUS; cpu_id++) {
+ if (cache_topology[cpu][cache_level] == cache_topology[cpu_id][cache_level])
+ cpumask_set_cpu(cpu_id, sc_mask);
+ }
+
+ if (cpumask_subset(sc_mask, cpu_mask))
+ break;
+ }
+}
+
/*
* cpu topology table
*/
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index 58cbe18d825c..c6ed727e453c 100644
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -93,6 +93,9 @@ void update_siblings_masks(unsigned int cpu);
void remove_cpu_topology(unsigned int cpuid);
void reset_cpu_topology(void);
int parse_acpi_topology(void);
+void topology_parse_cpu_caches(struct device_node *cpu_node, int cpu);
+void find_subset_of_share_cache(const struct cpumask *cpu_mask, int cpu,
+ struct cpumask *sc_mask);
I still have no idea what this last function is supposed to do.
And very odd indentation, did you run checkpatch on this?
totally confused,
greg k-h
