diff --git a/hbt/src/perf_event/BPerfEventsGroup.cpp b/hbt/src/perf_event/BPerfEventsGroup.cpp
index e803f1eb..52a6c89d 100644
--- a/hbt/src/perf_event/BPerfEventsGroup.cpp
+++ b/hbt/src/perf_event/BPerfEventsGroup.cpp
@@ -263,7 +263,7 @@ int BPerfEventsGroup::syncCpu_(__u32 cpu, int leader_fd) {
   return ::bpf_prog_test_run_opts(leader_fd, &opts);
 }
 
-void BPerfEventsGroup::syncGlobal_() {
+void BPerfEventsGroup::syncGlobal_() const {
   int err;
 
   for (int cpu = 0; cpu < cpu_cnt_; cpu++) {
@@ -497,7 +497,7 @@ int BPerfEventsGroup::preparePerThreadBPerf_(bperf_leader_cgroup* skel) {
 
 std::vector<struct bpf_perf_event_value> BPerfEventsGroup::readFromBpf_(
     int fd,
-    __u64 id) {
+    __u64 id) const {
   std::vector<struct bpf_perf_event_value> values(
       (size_t)cpu_cnt_ * BPERF_MAX_GROUP_SIZE);
   if (!enabled_) {
@@ -518,7 +518,7 @@ int BPerfEventsGroup::read(
     struct bpf_perf_event_value* output,
     int fd,
     __u64 id,
-    bool skip_offset) {
+    bool skip_offset) const {
   auto event_cnt = confs_.size();
 
   auto values = readFromBpf_(fd, id);
@@ -550,7 +550,7 @@ int BPerfEventsGroup::readPerCpu(
         int,
         std::array<struct bpf_perf_event_value, BPERF_MAX_GROUP_SIZE>>& output,
     int fd,
-    __u64 id) {
+    __u64 id) const {
   auto event_cnt = confs_.size();
 
   auto values = readFromBpf_(fd, id);
@@ -569,11 +569,11 @@ int BPerfEventsGroup::readPerCpu(
 
 int BPerfEventsGroup::readGlobal(
     struct bpf_perf_event_value* output,
-    bool skip_offset) {
+    bool skip_offset) const {
   return read(output, global_output_fd_, 0, skip_offset);
 }
 
-bool BPerfEventsGroup::readGlobal(ReadValues& rv, bool skip_offset) {
+bool BPerfEventsGroup::readGlobal(ReadValues& rv, bool skip_offset) const {
   const auto num_events = rv.getNumEvents();
   HBT_ARG_CHECK_EQ(confs_.size(), rv.getNumEvents());
 
@@ -589,11 +589,11 @@ bool BPerfEventsGroup::readGlobal(ReadValues& rv, bool skip_offset) {
 int BPerfEventsGroup::readGlobalPerCpu(
     std::
         map<int, std::array<struct bpf_perf_event_value, BPERF_MAX_GROUP_SIZE>>&
-            output) {
+            output) const {
   return readPerCpu(output, global_output_fd_, 0);
 }
 
-bool BPerfEventsGroup::readGlobalPerCpu(std::map<int, ReadValues>& rv) {
+bool BPerfEventsGroup::readGlobalPerCpu(std::map<int, ReadValues>& rv) const {
   std::map<int, std::array<struct bpf_perf_event_value, BPERF_MAX_GROUP_SIZE>>
       output;
   int numEvents = readGlobalPerCpu(output);
@@ -604,13 +604,12 @@ bool BPerfEventsGroup::readGlobalPerCpu(std::map<int, ReadValues>& rv) {
   return numEvents > 0;
 }
 
-int BPerfEventsGroup::readCgroup(
-    struct bpf_perf_event_value* output,
-    __u64 id) {
+int BPerfEventsGroup::readCgroup(struct bpf_perf_event_value* output, __u64 id)
+    const {
   return read(output, cgroup_output_fd_, id, true /* skip_offset */);
 }
 
-bool BPerfEventsGroup::readCgroup(ReadValues& rv, __u64 id) {
+bool BPerfEventsGroup::readCgroup(ReadValues& rv, __u64 id) const {
   const auto num_events = rv.getNumEvents();
   HBT_ARG_CHECK_EQ(confs_.size(), rv.getNumEvents());
 
diff --git a/hbt/src/perf_event/BPerfEventsGroup.h b/hbt/src/perf_event/BPerfEventsGroup.h
index 0f4530eb..85500d8e 100644
--- a/hbt/src/perf_event/BPerfEventsGroup.h
+++ b/hbt/src/perf_event/BPerfEventsGroup.h
@@ -70,17 +70,18 @@ class BPerfEventsGroup {
   bool removeCgroup(__u64 id);
 
   // eBPF like interface to read counters from all CPUs and accumulate them.
-  int readGlobal(struct bpf_perf_event_value* output, bool skip_offset = false);
-  bool readGlobal(ReadValues& rv, bool skip_offset = false);
+  int readGlobal(struct bpf_perf_event_value* output, bool skip_offset = false)
+      const;
+  bool readGlobal(ReadValues& rv, bool skip_offset = false) const;
   int readGlobalPerCpu(
       std::map<
           int,
           std::array<struct bpf_perf_event_value, BPERF_MAX_GROUP_SIZE>>&
-          output);
-  bool readGlobalPerCpu(std::map<int, ReadValues>& rv);
+          output) const;
+  bool readGlobalPerCpu(std::map<int, ReadValues>& rv) const;
 
-  int readCgroup(struct bpf_perf_event_value* output, __u64 id);
-  bool readCgroup(ReadValues& rv, __u64 id);
+  int readCgroup(struct bpf_perf_event_value* output, __u64 id) const;
+  bool readCgroup(ReadValues& rv, __u64 id) const;
 
  protected:
   const EventConfs confs_;
@@ -128,13 +129,13 @@ class BPerfEventsGroup {
   //     read(&offset_);
   struct bpf_perf_event_value offsets_[BPERF_MAX_GROUP_SIZE];
 
-  std::vector<struct bpf_perf_event_value> readFromBpf_(int fd, __u64 id);
+  std::vector<struct bpf_perf_event_value> readFromBpf_(int fd, __u64 id) const;
 
   int read(
       struct bpf_perf_event_value* output,
       int fd,
       __u64 id,
-      bool skip_offset = false);
+      bool skip_offset = false) const;
 
   int readPerCpu(
       std::map<
@@ -142,14 +143,14 @@ class BPerfEventsGroup {
           std::array<struct bpf_perf_event_value, BPERF_MAX_GROUP_SIZE>>&
           output,
       int fd,
-      __u64 id);
+      __u64 id) const;
 
   int reloadSkel_(struct bperf_attr_map_elem* entry);
   int loadPerfEvent_(struct bperf_leader_cgroup* skel);
 
   static int syncCpu_(__u32 cpu, int leader_pd);
   static void toReadValues(ReadValues& rv, struct bpf_perf_event_value*);
-  void syncGlobal_();
+  void syncGlobal_() const;
 
   // For per thread monitoring
   bool per_thread_;