[LNT] r300680 - [cPerf] Timestamp MMAP and MMAP2 events

[Kristof Beyls via llvm-commits]

Author: kbeyls
Date: Wed Apr 19 06:50:17 2017
New Revision: 300680

URL: http://llvm.org/viewvc/llvm-project?rev=300680&view=rev
Log:
[cPerf] Timestamp MMAP and MMAP2 events

Events in the perf event stream may not be in order. We don't generally
care if samples are out of order because we don't use their timestamp
information. However we *do* care if a sample appears before the MMAP
event that defined which file was mapped to its PC.

MMAP events are timestamped. Change the data structure for PC->mmap
lookups so that we can query the state of the address space mappings at
a particular time. This isn't mega efficient, but we don't expect many
MMAPs.

Patch by James Molloy.


Modified:
    lnt/trunk/lnt/testing/profile/cPerf.cpp

Modified: lnt/trunk/lnt/testing/profile/cPerf.cpp
URL: http://llvm.org/viewvc/llvm-project/lnt/trunk/lnt/testing/profile/cPerf.cpp?rev=300680&r1=300679&r2=300680&view=diff
==============================================================================
--- lnt/trunk/lnt/testing/profile/cPerf.cpp (original)
+++ lnt/trunk/lnt/testing/profile/cPerf.cpp Wed Apr 19 06:50:17 2017
@@ -232,6 +232,12 @@ struct perf_trace_event_type {
   char str[64];
 };
 
+struct perf_sample_id {
+  uint32_t pid, tid;
+  uint64_t time;
+  uint64_t id;
+};
+
 //===----------------------------------------------------------------------===//
 // Readers for nm and objdump output
 //===----------------------------------------------------------------------===//
@@ -433,7 +439,7 @@ private:
   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, size_t> CurrentMaps;
+  std::map<uint64_t, std::map<uint64_t, size_t>> CurrentMaps;
 
   PyObject *Functions, *TopLevelCounters;
   std::vector<PyObject*> Lines;
@@ -519,36 +525,54 @@ unsigned char *PerfReader::readEvent(uns
     auto MapID = Maps.size();
     Maps.push_back({E->start, E->start + E->extent, E->filename});
 
-    // Clear out the current range if applicable.
-    auto L = CurrentMaps.lower_bound(E->start);
-    auto H = CurrentMaps.upper_bound(E->start + E->extent);
-    CurrentMaps.erase(L, H);
-
-    CurrentMaps.insert({E->start, MapID});
+    // FIXME: use EventLayouts.begin()->second!
+    perf_sample_id *ID =
+        (perf_sample_id *)(Buf + E->header.size - sizeof(perf_sample_id));
+    auto &CurrentMap = CurrentMaps[ID->time];
+    CurrentMap.insert({E->start, MapID});
   }
   if (E->header.type == PERF_RECORD_MMAP2) {
     perf_event_mmap2 *E = (perf_event_mmap2 *)Buf;
     auto MapID = Maps.size();
     Maps.push_back({E->start, E->start + E->extent, E->filename});
 
-    // Clear out the current range if applicable.
-    auto L = CurrentMaps.lower_bound(E->start);
-    auto H = CurrentMaps.upper_bound(E->start + E->extent);
-    CurrentMaps.erase(L, H);
-
-    CurrentMaps.insert({E->start, MapID});
+    // FIXME: use EventLayouts.begin()->second!
+    perf_sample_id *ID =
+        (perf_sample_id *)(Buf + E->header.size - sizeof(perf_sample_id));
+    auto &CurrentMap = CurrentMaps[ID->time];
+    CurrentMap.insert({E->start, MapID});
   }
 
   if (E->header.type != PERF_RECORD_SAMPLE)
     return &Buf[E->header.size];
-
   
   auto NewE = parseEvent(((unsigned char*)E) + sizeof(perf_event_header),
                          EventLayouts.begin()->second);
   auto EventID = NewE.id;
   auto PC = NewE.ip;
-  auto MapID = std::prev(CurrentMaps.upper_bound(PC))->second;
 
+  // Search for the map corresponding to this sample. Search backwards through
+  // time, discarding any maps created after our timestamp.
+  size_t MapID = ~0UL;
+  for (auto I = CurrentMaps.rbegin(), E = CurrentMaps.rend();
+       I != E; ++I) {
+    if (I->first > NewE.time)
+      continue;
+    
+    auto NewI = I->second.upper_bound(PC);
+    if (NewI == I->second.begin())
+      continue;
+    --NewI;
+
+    if (NewI->first > PC)
+      continue;
+    MapID = NewI->second;
+    break;
+  }
+  if (MapID == ~0UL)
+    return &Buf[E->header.size];
+  assert(MapID != ~0UL);
+  
   assert(EventIDs.count(EventID));
   Events[MapID][PC][EventIDs[EventID]] += NewE.period;