Slightly safer linux counters

simdjson · Apr 21, 2023 · abf3d7d · abf3d7d
1 parent 3c313b8
commit abf3d7d
Showing 1 changed file with 19 additions and 34 deletions.
diff --git a/benchmark/linux/linux-perf-events.h b/benchmark/linux/linux-perf-events.h
@@ -1,22 +1,13 @@
-// https://github.com/WojciechMula/toys/blob/master/000helpers/linux-perf-events.h
 #pragma once
 #ifdef __linux__
-#ifdef __has_include
-#if __has_include(<asm/unistd.h>)
-#include <asm/unistd.h>       // for __NR_perf_event_open
-#else
-#warning "Header asm/unistd.h cannot be found though it is a linux system. Are linux headers missing?"
-#endif
-#else // no __has_include
-// Please insure that linux headers have been installed.
+
 #include <asm/unistd.h>       // for __NR_perf_event_open
-#endif
 #include <linux/perf_event.h> // for perf event constants
 #include <sys/ioctl.h>        // for ioctl
 #include <unistd.h>           // for syscall
 
 #include <cerrno>  // for errno
-#include <cstring> // for std::memset
+#include <cstring> // for memset
 #include <stdexcept>
 
 #include <iostream>
@@ -28,13 +19,11 @@ template <int TYPE = PERF_TYPE_HARDWARE> class LinuxEvents {
   perf_event_attr attribs{};
   size_t num_events{};
   std::vector<uint64_t> temp_result_vec{};
-  std::vector<uint64_t> result{};
-  std::vector<int> fds{};
-  bool quiet;
+  std::vector<uint64_t> ids{};
 
 public:
-  explicit LinuxEvents(std::vector<int> config_vec, bool _quiet=false) : fd(0), working(true), quiet{_quiet} {
-    std::memset(&attribs, 0, sizeof(attribs));
+  explicit LinuxEvents(std::vector<int> config_vec) : fd(0), working(true) {
+    memset(&attribs, 0, sizeof(attribs));
     attribs.type = TYPE;
     attribs.size = sizeof(attribs);
     attribs.disabled = 1;
@@ -49,30 +38,25 @@ template <int TYPE = PERF_TYPE_HARDWARE> class LinuxEvents {
 
     int group = -1; // no group
     num_events = config_vec.size();
-    result.resize(config_vec.size());
+    ids.resize(config_vec.size());
     uint32_t i = 0;
     for (auto config : config_vec) {
       attribs.config = config;
       int _fd = static_cast<int>(syscall(__NR_perf_event_open, &attribs, pid, cpu, group, flags));
       if (_fd == -1) {
         report_error("perf_event_open");
       }
-      fd = _fd; // fd tracks the last _fd value.
-      fds.push_back(fd);
-      ioctl(fd, PERF_EVENT_IOC_ID, &result[i++]);
+      ioctl(_fd, PERF_EVENT_IOC_ID, &ids[i++]);
       if (group == -1) {
-        group = fd;
+        group = _fd;
+        fd = _fd;
       }
     }
 
     temp_result_vec.resize(num_events * 2 + 1);
   }
 
-  ~LinuxEvents() {
-   for (auto tfd : fds) {
-      if (tfd != -1) { close(tfd); }
-    }
-  }
+  ~LinuxEvents() { if (fd != -1) { close(fd); } }
 
   inline void start() {
     if (fd != -1) {
@@ -97,24 +81,25 @@ template <int TYPE = PERF_TYPE_HARDWARE> class LinuxEvents {
       }
     }
     // our actual results are in slots 1,3,5, ... of this structure
-    // we really should be checking our result obtained earlier to be safe
     for (uint32_t i = 1; i < temp_result_vec.size(); i += 2) {
       results[i / 2] = temp_result_vec[i];
     }
+    for (uint32_t i = 2; i < temp_result_vec.size(); i += 2) {
+      if(ids[i/2-1] != temp_result_vec[i]) {
+        report_error("event mismatch");
+      }
+    }
+
+
   }
 
   bool is_working() {
     return working;
   }
 
 private:
-  void report_error(const std::string &context) {
-    if (!quiet) {
-      if (working) {
-        std::cerr << (context + ": " + std::string(strerror(errno))) << std::endl;
-      }
-    }
+  void report_error(const std::string &) {
     working = false;
   }
 };
-#endif
+#endif