i sent an old version of this around a year or two ago, which devolved
into a discussion around how annoying the repeated cpu info is in dmesg.
that's since been addressed, so i'm trying this out again.

if an intel cpu provides information about the type of cpu, this adds it
to the topology line in dmesg output. this is particularly interesting
on hybrid systems.

there are MSRs on recent amd chips that can tell zen 4 vs 4c or 5 vs 5c
cores apart, but i dont have one to test with.

Index: amd64/identcpu.c
===================================================================
RCS file: /cvs/src/sys/arch/amd64/amd64/identcpu.c,v
diff -u -p -r1.151 identcpu.c
--- amd64/identcpu.c	26 Jun 2025 12:17:27 -0000	1.151
+++ amd64/identcpu.c	23 Jul 2025 07:31:25 -0000
@@ -831,6 +843,7 @@ cpu_topology(struct cpu_info *ci)
 	u_int32_t apicid, max_apicid = 0, max_coreid = 0;
 	u_int32_t smt_bits = 0, core_bits, pkg_bits = 0;
 	u_int32_t smt_mask = 0, core_mask, pkg_mask = 0;
+	const char *type = NULL;
 
 	/* We need at least apicid at CPUID 1 */
 	if (ci->ci_cpuid_level < 1)
@@ -890,20 +903,35 @@ cpu_topology(struct cpu_info *ci)
 		ci->ci_smt_id = apicid & smt_mask;
 		ci->ci_core_id = (apicid & core_mask) >> smt_bits;
 		ci->ci_pkg_id = (apicid & pkg_mask) >> pkg_bits;
+
+		if (cpuid_level >= 0x1a) {
+			CPUID_LEAF(0x1a, 0, eax, ebx, ecx, edx);
+			switch ((eax >> 24) & 0xff) {
+			case 0x20:
+				type = "efficiency";
+				break;
+			case 0x40:
+				type = "performance";
+				break;
+			}
+		}
 	} else
 		goto no_topology;
 #ifdef DEBUG
 	printf("cpu%d: smt %u, core %u, pkg %u "
 		"(apicid 0x%x, max_apicid 0x%x, max_coreid 0x%x, smt_bits 0x%x, smt_mask 0x%x, "
-		"core_bits 0x%x, core_mask 0x%x, pkg_bits 0x%x, pkg_mask 0x%x)\n",
+		"core_bits 0x%x, core_mask 0x%x, pkg_bits 0x%x, pkg_mask 0x%x)",
 		ci->ci_cpuid, ci->ci_smt_id, ci->ci_core_id, ci->ci_pkg_id,
 		apicid, max_apicid, max_coreid, smt_bits, smt_mask, core_bits,
 		core_mask, pkg_bits, pkg_mask);
 #else
-	printf("cpu%d: smt %u, core %u, package %u\n", ci->ci_cpuid,
+	printf("cpu%d: smt %u, core %u, package %u", ci->ci_cpuid,
 		ci->ci_smt_id, ci->ci_core_id, ci->ci_pkg_id);
 
 #endif
+	if (type != NULL)
+		printf(", %s core", type);
+	printf("\n");
 	return;
 	/* We can't map, so consider ci_core_id as ci_cpuid */
 no_topology: