Record maps per process rather than globally

If a perf.data file is coming from whole-system or multi-process
profiling then the MMAP(2) events may have overlapping address ranges.
This can cause samples to be incorrectly attributed to whatever the most
recent process to start was rather than the actual process from which
the sample came from.

To get around this, simply keep track of a separate set of maps per
process instead.

Change-Id: I671bc3f281d192d5ee4dcdfe9b0f13a865126a23

Author: georges-arm

lnt/testing/profile/cPerf.cpp

@@ -679,7 +679,7 @@ class PerfReader {
   std::map<const char *, uint64_t> TotalEvents;
   std::map<uint64_t, std::map<const char *, uint64_t>> TotalEventsPerMap;
   std::vector<Map> Maps;
-  std::map<uint64_t, std::map<uint64_t, EventDesc>> CurrentMaps;
+  std::map<uint64_t, std::map<uint64_t, std::map<uint64_t, EventDesc>>> CurrentMaps;
 
   PyObject *Functions, *TopLevelCounters;
   std::vector<PyObject*> Lines;
@@ -850,7 +850,7 @@ void PerfReader::registerNewMapping(unsigned char *Buf, const char *Filename) {
   // FIXME: The first EventID is used for every event.
   // FIXME: The code assumes perf_event_attr.sample_id_all is set.
   uint64_t Time = getTimeFromSampleId(EndOfEvent, EventLayouts.begin()->second);
-  auto &CurrentMap = CurrentMaps[Time];
+  auto &CurrentMap = CurrentMaps[E->pid][Time];
   CurrentMap.insert({E->start, { E->start, End, MapID}});
 }
 
@@ -882,8 +882,8 @@ unsigned char *PerfReader::readEvent(unsigned char *Buf) {
     // Search for the map corresponding to this sample. Search backwards through
     // time, discarding any maps created after our timestamp.
     uint64_t MapID = ~0ULL;
-    for (auto I = CurrentMaps.rbegin(), E = CurrentMaps.rend();
-         I != E; ++I) {
+    auto &MapsForPid = CurrentMaps[E->pid];
+    for (auto I = MapsForPid.rbegin(), E = MapsForPid.rend(); I != E; ++I) {
       if (I->first > NewE.time)
         continue;