feat(sampling) Remove tracepoints based process switch recording support

This PR removes support for process switch recording based on
tracepoints.

lo2s now requires support for PERF_RECORD_SWITCH, which was added in the
4.3 kernel and is widely backported to older systems. Neither Taurus nor
the Levante installation at DKRZ lack PERF_RECORD_SWITCH support.

.github/workflows/cmake.yml

@@ -14,7 +14,6 @@ jobs:
         compiler: [g++-9, g++-10, clang++-10, clang++-11, clang++-12]
         build-type: [Debug, RelWithDebInfo]
         hw_breakpoint: [ON, OFF]
-        perf_record_switch: [ON, OFF]
         perf_clockid: [ON, OFF]
 
     runs-on: ${{ matrix.os }}
@@ -43,7 +42,7 @@ jobs:
       - name: Run CMake configure
         env:
           CXX: ${{ matrix.compiler }}
-        run: cmake . -DCMAKE_BUILD_TYPE=${{ matrix.build-type }} -DUSE_HW_BREAKPOINT_COMPAT=${{ matrix.hw_breakpoint }} -DUSE_PERF_CLOCKID=${{ matrix.perf_clockid }} -DUSE_PERF_RECORD_SWITCH=${{ matrix.perf_record_switch }}
+        run: cmake . -DCMAKE_BUILD_TYPE=${{ matrix.build-type }} -DUSE_HW_BREAKPOINT_COMPAT=${{ matrix.hw_breakpoint }} -DUSE_PERF_CLOCKID=${{ matrix.perf_clockid }}
       - name: Build
         run: make -j 2
       - name: Create source tarball

CMakeLists.txt

@@ -111,16 +111,12 @@ if(PkgConfig_FOUND)
 endif()
 
 
-CHECK_STRUCT_HAS_BITFIELD("struct perf_event_attr" context_switch linux/perf_event.h HAVE_PERF_RECORD_SWITCH)
-
 # configurable options
 CMAKE_DEPENDENT_OPTION(USE_RADARE "Enable Radare support." ON "Radare_FOUND" OFF)
 option(USE_HW_BREAKPOINT_COMPAT "Time synchronization fallback for old kernels without hardware breakpoint support." OFF)
 add_feature_info("USE_HW_BREAKPOINT_COMPAT" USE_HW_BREAKPOINT_COMPAT "Time synchronization fallback for old kernels without hardware breakpoint support.")
 option(USE_PERF_CLOCKID "Enables specifying a custom reference clock for recorded events" ON)
 add_feature_info("USE_PERF_CLOCKID" USE_PERF_CLOCKID "Enables specifying a custom reference clock for recorded events")
-CMAKE_DEPENDENT_OPTION(USE_PERF_RECORD_SWITCH "Uses PERF_RECORD_SWITCH for CPU Context Switches instead of the older tracepoint based solution" ON HAVE_PERF_RECORD_SWITCH OFF)
-add_feature_info("USE_PERF_RECORD_SWITCH" USE_PERF_RECORD_SWITCH "Uses PERF_RECORD_SWITCH for CPU Context Switches instead of the older tracepoint based solution")
 option(IWYU "Developer option for include what you use." OFF)
 option(UML_LOOK "Generate graphs with an UML look" OFF)
 add_feature_info("USE_RADARE" USE_RADARE "Use Radare to add instruction information to samples.")
@@ -139,6 +135,12 @@ if(NOT CLOCK_GETTIME_FOUND)
     unset(CMAKE_REQUIRED_LIBRARIES)
 endif()
 
+CHECK_STRUCT_HAS_BITFIELD("struct perf_event_attr" context_switch linux/perf_event.h HAVE_PERF_RECORD_SWITCH)
+
+if(NOT HAVE_PERF_RECORD_SWITCH)
+    message(FATAL_ERROR "lo2s requires support for perf context switch recording. Make sure that you are running on a kernel that support context_switch with perf_event_open")
+endif()
+
 # detect version of running kernel
 string(REGEX MATCH "[0-9]+\\.[0-9]+\\.[0-9]+" LINUX_VERSION ${CMAKE_SYSTEM_VERSION})
 
@@ -337,10 +339,6 @@ else()
     endif()
 endif()
 
-if(NOT USE_PERF_RECORD_SWITCH)
-    target_sources(lo2s PRIVATE src/perf/tracepoint/switch_writer.cpp)
-endif()
-
 configure_file(include/lo2s/build_config.hpp.in include/lo2s/build_config.hpp)
 
 # define include directory of target lo2s

include/lo2s/build_config.hpp.in

@@ -34,6 +34,4 @@
 
 #cmakedefine USE_PERF_CLOCKID
 
-#cmakedefine USE_PERF_RECORD_SWITCH
-
 #cmakedefine LO2S_COPYRIGHT_YEAR "@LO2S_COPYRIGHT_YEAR@"

include/lo2s/monitor/scope_monitor.hpp

@@ -30,10 +30,6 @@
 #include <lo2s/perf/sample/writer.hpp>
 #include <lo2s/perf/syscall/writer.hpp>
 
-#ifndef USE_PERF_RECORD_SWITCH
-#include <lo2s/perf/tracepoint/switch_writer.hpp>
-#endif
-
 #include <array>
 #include <chrono>
 #include <thread>
@@ -78,9 +74,6 @@ class ScopeMonitor : public PollMonitor
     std::unique_ptr<perf::sample::Writer> sample_writer_;
     std::unique_ptr<perf::counter::group::Writer> group_counter_writer_;
     std::unique_ptr<perf::counter::userspace::Writer> userspace_counter_writer_;
-#ifndef USE_PERF_RECORD_SWITCH
-    std::unique_ptr<perf::tracepoint::SwitchWriter> switch_writer_;
-#endif
 };
 } // namespace monitor
 } // namespace lo2s

include/lo2s/perf/event_reader.hpp

@@ -194,14 +194,12 @@ class EventReader
             case PERF_RECORD_MMAP2:
                 stop = crtp_this->handle((const RecordMmap2Type*)event_header_p);
                 break;
-#ifdef USE_PERF_RECORD_SWITCH
             case PERF_RECORD_SWITCH:
                 stop = crtp_this->handle((const RecordSwitchType*)event_header_p);
                 break;
             case PERF_RECORD_SWITCH_CPU_WIDE:
                 stop = crtp_this->handle((const RecordSwitchCpuWideType*)event_header_p);
                 break;
-#endif
             case PERF_RECORD_THROTTLE: /* fall-through */
             case PERF_RECORD_UNTHROTTLE:
                 throttle_samples++;

include/lo2s/perf/sample/reader.hpp

@@ -123,10 +123,8 @@ class Reader : public EventReader<T>
         // name of a task.  This is used to write a meaningful name for any
         // traced thread to the archive.
         perf_attr.comm = 1;
-
-#ifdef USE_PERF_RECORD_SWITCH
         perf_attr.context_switch = 1;
-#endif
+
         // We need this to get all mmap_events
         if (enable_on_exec)
         {

include/lo2s/perf/sample/writer.hpp

@@ -66,10 +66,8 @@ class Writer : public Reader<Writer>
     bool handle(const Reader::RecordSampleType* sample);
     bool handle(const Reader::RecordMmapType* mmap_event);
     bool handle(const Reader::RecordCommType* comm);
-#ifdef USE_PERF_RECORD_SWITCH
     bool handle(const Reader::RecordSwitchCpuWideType* context_switch);
     bool handle(const Reader::RecordSwitchType* context_switch);
-#endif
 
     void end();
 

src/monitor/scope_monitor.cpp

@@ -45,11 +45,7 @@ namespace monitor
 ScopeMonitor::ScopeMonitor(ExecutionScope scope, MainMonitor& parent, bool enable_on_exec)
 : PollMonitor(parent.trace(), scope.name(), config().perf_read_interval), scope_(scope)
 {
-#ifndef USE_PERF_RECORD_SWITCH
-    if (config().sampling)
-#else
     if (config().sampling || scope.is_cpu())
-#endif
     {
         sample_writer_ =
             std::make_unique<perf::sample::Writer>(scope, parent, parent.trace(), enable_on_exec);
@@ -76,14 +72,6 @@ ScopeMonitor::ScopeMonitor(ExecutionScope scope, MainMonitor& parent, bool enabl
         add_fd(userspace_counter_writer_->fd());
     }
 
-#ifndef USE_PERF_RECORD_SWITCH
-    if (scope.is_cpu())
-    {
-        switch_writer_ =
-            std::make_unique<perf::tracepoint::SwitchWriter>(scope.as_cpu(), parent.trace());
-    }
-#endif
-
     // note: start() can now be called
 }
 
@@ -128,12 +116,6 @@ void ScopeMonitor::monitor(int fd)
     {
         userspace_counter_writer_->read();
     }
-#ifndef USE_PERF_RECORD_SWITCH
-    if (switch_writer_ && (fd == timer_pfd().fd || fd == stop_pfd().fd))
-    {
-        switch_writer_->read();
-    }
-#endif
 }
 } // namespace monitor
 } // namespace lo2s

src/perf/sample/writer.cpp

@@ -154,7 +154,6 @@ otf2::chrono::time_point Writer::adjust_timepoints(otf2::chrono::time_point tp)
     return tp;
 }
 
-#ifdef USE_PERF_RECORD_SWITCH
 bool Writer::handle(const Reader::RecordSwitchCpuWideType* context_switch)
 {
     assert(scope_.is_cpu());
@@ -210,7 +209,6 @@ void Writer::update_calling_context(Process process, Thread thread, otf2::chrono
     }
 }
 
-#endif
 bool Writer::handle(const Reader::RecordCommType* comm)
 {
     if (!scope_.is_cpu())