New subject: [PATCH 2/2] task: show the NUMA information in task_cpu

Tuesday, 11 August 2026

Add cpu_to_nid function which we can use to get the NUMA node id
by the cpu id.

  1.) For live mode: use /sys/ files to get the cpu_to_nid.
	     This method will succeed 100%.

  2.) For vmcore mode: use "numa_node" symbol to get the cpu_to_nid.
	     If CONFIG_USE_PERCPU_NUMA_NODE_ID does not defined in kernel,
	     this method will fail.

Signed-off-by: Huang Shijie <huangsj(a)hygon.cn&gt;
---
 defs.h   |  2 ++
 kernel.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 main.c   |  1 +
 3 files changed, 69 insertions(+)

diff --git a/defs.h b/defs.h
index e3027e2..7e1515a 100644
--- a/defs.h
+++ b/defs.h
@@ -6044,6 +6044,8 @@ ulong do_maple_tree(ulong, int, struct list_pair *);
 void help_init(void);
 void cmd_usage(char *, int);
 void display_version(void);
+int cpu_to_nid(int cpu);
+void numa_init(void);
 void display_help_screen(char *);
 #ifdef ARM
 #define dump_machdep_table(X) arm_dump_machdep_table(X)
diff --git a/kernel.c b/kernel.c
index e53038d..32230fb 100644
--- a/kernel.c
+++ b/kernel.c
@@ -12221,3 +12221,69 @@ out:
 	pc->error_fp = error_fp_save;
 }
 #endif
+
+static int *cpu_to_nid_map;
+
+int
+cpu_to_nid(int cpu)
+{
+	if (!cpu_to_nid_map || cpu < 0 || cpu >= kt->cpus)
+		return -1;
+	if (vt->numnodes == 1)
+		return 0;
+	return cpu_to_nid_map[cpu];
+}
+
+static void
+cpu_to_nid_init(void)
+{
+	int i, j;
+	int fd;
+	char buf[64];
+
+	cpu_to_nid_map = malloc(kt->cpus * sizeof(int));
+	if (vt->numnodes == 1)
+		return;
+
+	memset(cpu_to_nid_map, -1, kt->cpus * sizeof(int));
+
+	if (ACTIVE()) {
+		for (i = 0; i < kt->cpus; i++) {
+			for (j = 0; j < vt->numnodes; j++) {
+				memset(buf, 0, sizeof(buf));
+				sprintf(buf, "/sys/devices/system/cpu/cpu%d/node%d", i, j);
+
+				fd = open(buf, O_RDONLY);
+				if (fd > 0) {
+					cpu_to_nid_map[i] = j;
+					close(fd);
+					break;
+				}
+			}
+		}
+	} else {
+		int cpu;
+
+		if (symbol_exists("numa_node")) {
+			ulong base = symbol_value("numa_node");
+
+			for (cpu = 0; cpu < kt->cpus; cpu++) {
+				ulong addr = base + kt->__per_cpu_offset[cpu];
+				int nid;
+
+				if (readmem(addr, KVADDR, &nid, sizeof(int),
+				    "numa_node", RETURN_ON_ERROR|QUIET))
+					cpu_to_nid_map[cpu] = nid;
+			}
+		} else {
+			error(WARNING,
+			    "numa_node symbol not found in vmcore\n");
+		}
+	}
+}
+
+void
+numa_init(void)
+{
+	cpu_to_nid_init();
+}
diff --git a/main.c b/main.c
index d5f8486..a8c77f8 100644
--- a/main.c
+++ b/main.c
@@ -793,6 +793,7 @@ main_loop(void)
 			kernel_init();
 			machdep_init(POST_GDB);
         		vm_init();
+			numa_init();
 			machdep_init(POST_VM);
         		module_init();
         		help_init();
-- 
2.53.0


    

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[PATCH 1/2] add cpu_to_nid function