add interval probe type

README.md

@@ -169,8 +169,8 @@ Attach script to hardware events (PMCs), executing once every provided count or
 `hardware:cache-references:1000000`
 `hardware:cache-references:`
 
-### timers
-Run the script at specified time intervals:
+### profile
+Run the script on all CPUs at specified time intervals:
 
 `profile:hz:99 { ... }`
 
@@ -180,6 +180,13 @@ Run the script at specified time intervals:
 
 `profile:us:1500 { ... }`
 
+### interval
+Run the script once per interval, for printing interval output:
+
+`interval:s:1 { ... }`
+
+`interval:ms:20 { ... }`
+
 ### Multiple attachment points
 A single probe can be attached to multiple events:
 

src/ast/semantic_analyser.cpp

@@ -497,6 +497,15 @@ void SemanticAnalyser::visit(AttachPoint &ap)
     else if (ap.freq <= 0)
       err_ << "profile frequency should be a positive integer" << std::endl;
   }
+  else if (ap.provider == "interval") {
+    if (ap.target == "")
+      err_ << "interval probe must have unit of time" << std::endl;
+    else if (ap.target != "ms" &&
+             ap.target != "s")
+      err_ << ap.target << " is not an accepted unit of time" << std::endl;
+    if (ap.func != "")
+      err_ << "interval probe must have an integer frequency" << std::endl;
+  }
   else if (ap.provider == "software") {
     if (ap.target == "")
       err_ << "software probe must have a software event name" << std::endl;

src/attached_probe.cpp

@@ -40,6 +40,7 @@ bpf_prog_type progtype(ProbeType t)
     case ProbeType::uretprobe:  return BPF_PROG_TYPE_KPROBE; break;
     case ProbeType::tracepoint: return BPF_PROG_TYPE_TRACEPOINT; break;
     case ProbeType::profile:      return BPF_PROG_TYPE_PERF_EVENT; break;
+    case ProbeType::interval:      return BPF_PROG_TYPE_PERF_EVENT; break;
     case ProbeType::software:   return BPF_PROG_TYPE_PERF_EVENT; break;
     case ProbeType::hardware:   return BPF_PROG_TYPE_PERF_EVENT; break;
     default: abort();
@@ -67,6 +68,9 @@ AttachedProbe::AttachedProbe(Probe &probe, std::tuple<uint8_t *, uintptr_t> func
     case ProbeType::profile:
       attach_profile();
       break;
+    case ProbeType::interval:
+      attach_interval();
+      break;
     case ProbeType::software:
       attach_software();
       break;
@@ -105,6 +109,7 @@ AttachedProbe::~AttachedProbe()
       err = bpf_detach_tracepoint(probe_.path.c_str(), eventname().c_str());
       break;
     case ProbeType::profile:
+    case ProbeType::interval:
     case ProbeType::software:
     case ProbeType::hardware:
       break;
@@ -327,6 +332,37 @@ void AttachedProbe::attach_profile()
   }
 }
 
+void AttachedProbe::attach_interval()
+{
+  int pid = -1;
+  int group_fd = -1;
+  int cpu = 0;
+
+  uint64_t period, freq;
+  if (probe_.path == "s")
+  {
+    period = probe_.freq * 1e9;
+    freq = 0;
+  }
+  else if (probe_.path == "ms")
+  {
+    period = probe_.freq * 1e6;
+    freq = 0;
+  }
+  else
+  {
+    abort();
+  }
+
+  int perf_event_fd = bpf_attach_perf_event(progfd_, PERF_TYPE_SOFTWARE,
+      PERF_COUNT_SW_CPU_CLOCK, period, freq, pid, cpu, group_fd);
+
+  if (perf_event_fd < 0)
+    throw std::runtime_error("Error attaching probe: " + probe_.name);
+
+  perf_event_fds_.push_back(perf_event_fd);
+}
+
 void AttachedProbe::attach_software()
 {
   int pid = -1;

src/attached_probe.h

@@ -27,6 +27,7 @@ private:
   void attach_uprobe();
   void attach_tracepoint();
   void attach_profile();
+  void attach_interval();
   void attach_software();
   void attach_hardware();
 

src/types.cpp

@@ -57,6 +57,8 @@ ProbeType probetype(const std::string &type)
     return ProbeType::tracepoint;
   else if (type == "profile")
     return ProbeType::profile;
+  else if (type == "interval")
+    return ProbeType::interval;
   else if (type == "software")
     return ProbeType::software;
   else if (type == "hardware")

src/types.h

@@ -51,6 +51,7 @@ enum class ProbeType
   uretprobe,
   tracepoint,
   profile,
+  interval,
   software,
   hardware,
 };

tests/bpftrace.cpp

@@ -59,6 +59,14 @@ void check_profile(Probe &p, const std::string &unit, int freq, const std::strin
   EXPECT_EQ("profile:" + unit + ":" + std::to_string(freq), p.name);
 }
 
+void check_interval(Probe &p, const std::string &unit, int freq, const std::string &prog_name)
+{
+  EXPECT_EQ(ProbeType::interval, p.type);
+  EXPECT_EQ(freq, p.freq);
+  EXPECT_EQ(prog_name, p.prog_name);
+  EXPECT_EQ("interval:" + unit + ":" + std::to_string(freq), p.name);
+}
+
 void check_software(Probe &p, const std::string &unit, int freq, const std::string &prog_name)
 {
   EXPECT_EQ(ProbeType::software, p.type);
@@ -325,6 +333,22 @@ TEST(bpftrace, add_probes_profile)
   check_profile(bpftrace.get_probes().at(0), "ms", 997, probe_prog_name);
 }
 
+TEST(bpftrace, add_probes_interval)
+{
+  ast::AttachPoint a("interval", "s", 1);
+  ast::AttachPointList attach_points = { &a };
+  ast::Probe probe(&attach_points, nullptr, nullptr);
+
+  StrictMock<MockBPFtrace> bpftrace;
+
+  EXPECT_EQ(0, bpftrace.add_probe(probe));
+  EXPECT_EQ(1, bpftrace.get_probes().size());
+  EXPECT_EQ(0, bpftrace.get_special_probes().size());
+
+  std::string probe_prog_name = "interval:s:1";
+  check_interval(bpftrace.get_probes().at(0), "s", 1, probe_prog_name);
+}
+
 TEST(bpftrace, add_probes_software)
 {
   ast::AttachPoint a("software", "faults", 1000);

tests/parser.cpp

@@ -260,6 +260,14 @@ TEST(Parser, profile_probe)
       "  int: 1\n");
 }
 
+TEST(Parser, interval_probe)
+{
+  test("interval:s:1 { 1 }",
+      "Program\n"
+      " interval:s:1\n"
+      "  int: 1\n");
+}
+
 TEST(Parser, software_probe)
 {
   test("software:faults:1000 { 1 }",