From adf5c8b7e727f436992ebc1cbcc75df651bc627f Mon Sep 17 00:00:00 2001
From: Brent Cook <busterb@gmail.com>
Date: Thu, 26 Mar 2026 07:31:54 -0500
Subject: [PATCH] only display online CPUs in output

coreCount now reflects only the schedulable CPUs. With hw.smt=0 on a
4-core/8-thread machine, coreCount becomes 4, so btop allocates 4
display slots instead of 8.

The collect loop now also checks CPUSTATS_ONLINE for each CPU and skips
offline CPUs, such as disabled hyperthreads.
---
 src/openbsd/btop_collect.cpp | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/src/openbsd/btop_collect.cpp b/src/openbsd/btop_collect.cpp
index 263cfd58..b250d027 100644
--- a/src/openbsd/btop_collect.cpp
+++ b/src/openbsd/btop_collect.cpp
@@ -127,7 +127,7 @@ namespace Shared {
 		//? Shared global variables init
 		int mib[2];
 		mib[0] = CTL_HW;
-		mib[1] = HW_NCPU;
+		mib[1] = HW_NCPUONLINE;
 		int ncpu;
 		size_t len = sizeof(ncpu);
 		if (sysctl(mib, 2, &ncpu, &len, nullptr, 0) == -1) {
@@ -392,12 +392,21 @@ namespace Cpu {
 			Logger::error("failed to get load averages");
 		}
 
+		//? Read total physical CPU count for sysctl iteration
+		//? (may differ from coreCount when SMT is disabled via hw.smt=0).
+		int ncpu_total = Shared::coreCount;
+		{
+			int mib[] = {CTL_HW, HW_NCPU};
+			size_t len = sizeof(ncpu_total);
+			sysctl(mib, 2, &ncpu_total, &len, nullptr, 0);
+		}
+
 		auto cp_time = std::unique_ptr<struct cpustats[]>{
-			new struct cpustats[Shared::coreCount]
+			new struct cpustats[ncpu_total]
 		};
 		size_t size = sizeof(struct cpustats);
 		static int cpustats_mib[] = {CTL_KERN, KERN_CPUSTATS, /*fillme*/0};
-		for (int i = 0; i < Shared::coreCount; i++) {
+		for (int i = 0; i < ncpu_total; i++) {
 			cpustats_mib[2] = i;
 			if (sysctl(cpustats_mib, 3, &cp_time[i], &size, NULL, 0) == -1) {
 				Logger::error("sysctl kern.cpustats failed");
@@ -407,11 +416,16 @@ namespace Cpu {
 		long long global_idles = 0;
 		vector<long long> times_summed = {0, 0, 0, 0};
 
-		for (long i = 0; i < Shared::coreCount; i++) {
+		//? j iterates all physical CPUs; offline ones are skipped
+		//? i is the display slot index, incremented only for online CPUs
+		for (long i = 0, j = 0; j < ncpu_total; j++) {
+			if (!(cp_time[j].cs_flags & CPUSTATS_ONLINE))
+				continue;
+
 			vector<long long> times;
 			//? 0=user, 1=nice, 2=system, 3=idle
 			for (int x = 0; const unsigned int c_state : {CP_USER, CP_NICE, CP_SYS, CP_IDLE}) {
-				auto val = cp_time[i].cs_time[c_state];
+				auto val = cp_time[j].cs_time[c_state];
 				times.push_back(val);
 				times_summed.at(x++) += val;
 			}
@@ -426,7 +440,6 @@ namespace Cpu {
 				global_idles += idles;
 
 				//? Calculate cpu total for each core
-				if (i > Shared::coreCount) break;
 				const long long calc_totals = max(0ll, totals - core_old_totals.at(i));
 				const long long calc_idles = max(0ll, idles - core_old_idles.at(i));
 				core_old_totals.at(i) = totals;
@@ -441,7 +454,7 @@ namespace Cpu {
 				Logger::error("Cpu::collect() : {}", e.what());
 				throw std::runtime_error(fmt::format("collect() : {}", e.what()));
 			}
-
+			i++;
 		}
 
 		const long long calc_totals = max(1ll, global_totals - cpu_old.at("totals"));
@@ -1222,7 +1235,7 @@ namespace Proc {
 				}
 				toggle_children = -1;
 			}
-			
+
 			if (auto find_pid = (collapse != -1 ? collapse : expand); find_pid != -1) {
 				auto collapser = rng::find(current_procs, find_pid, &proc_info::pid);
 				if (collapser != current_procs.end()) {