simpleperf: prefer to use mmap2 records instead of mmap records.

When doing system wide recording, simpleperf spents a lot of time
in calling ApkInspector::FindElfInApkByOffset() in
UpdateMmapRecordForEmbeddedPath() in cmd_record.cpp (about 35%
main thread time). This is because app processes map many files
in the apk into the memory.
Actually we only need to change the maps of executable files in the
apk. However, mmap record doesn't show whether the mapped file is
executable. So switch to mmap2 record when possible. mmap2 record is
supported starting from kernel 3.16, and dumps more info than mmap
record, like the protect flag of the map. After switching to mmap2
records, the cost of calling ApkInspector::FindElfInApkByOffset()
is decreased to about 1% main thread time.

Also switch to dump mmap and comm records only for the first event
type.
Also avoid using IsRegularFile() in IsMappingOnlyExistInMemory, which
saves about 3% main thread time.
Also add a test to request mmap2 record support in Q.

Bug: none
Test: run simpleperf for system wide recording manually.
Test: run simpleperf_unit_test.

Change-Id: Ib0f42f509cb10b3242503d54d048f9c90885affa

1 files changed, 12 insertions, 15 deletions

diff --git a/simpleperf/cmd_record.cpp b/simpleperf/cmd_record.cpp
index 44b05c4b..2597629f 100644
--- a/simpleperf/cmd_record.cpp
+++ b/simpleperf/cmd_record.cpp
@@ -1027,11 +1027,11 @@ bool RecordCommand::DumpProcessMaps(pid_t pid, const std::unordered_set<pid_t>&
   const perf_event_attr& attr = *dumping_attr_id_.attr;
   uint64_t event_id = dumping_attr_id_.ids[0];
   for (const auto& map : thread_mmaps) {
-    if (map.executable == 0 && !event_selection_set_.RecordNotExecutableMaps()) {
+    if (!(map.prot & PROT_EXEC) && !event_selection_set_.RecordNotExecutableMaps()) {
       continue;
     }
-    MmapRecord record(attr, false, pid, pid, map.start_addr, map.len,
-                      map.pgoff, map.name, event_id, last_record_timestamp_);
+    Mmap2Record record(attr, false, pid, pid, map.start_addr, map.len,
+                      map.pgoff, map.prot, map.name, event_id, last_record_timestamp_);
     if (!ProcessRecord(&record)) {
       return false;
     }
@@ -1084,11 +1084,8 @@ bool RecordCommand::ProcessRecord(Record* record) {
 }
 
 template <typename MmapRecordType>
-bool IsMappingOnlyExistInMemory(MmapRecordType* record) {
-  return !(record->InKernel() ||
-      strcmp(record->filename, "[vdso]") == 0 ||
-      strstr(record->filename, "!/") != nullptr ||
-      IsRegularFile(record->filename));
+bool MapOnlyExistInMemory(MmapRecordType* record) {
+  return !record->InKernel() && MappedFileOnlyExistInMemory(record->filename);
 }
 
 bool RecordCommand::ShouldOmitRecord(Record* record) {
@@ -1100,9 +1097,9 @@ bool RecordCommand::ShouldOmitRecord(Record* record) {
     // dalvik-jit-code-cache and other maps that only exist in memory.
     switch (record->type()) {
       case PERF_RECORD_MMAP:
-        return IsMappingOnlyExistInMemory(static_cast<MmapRecord*>(record));
+        return MapOnlyExistInMemory(static_cast<MmapRecord*>(record));
       case PERF_RECORD_MMAP2:
-        return IsMappingOnlyExistInMemory(static_cast<Mmap2Record*>(record));
+        return MapOnlyExistInMemory(static_cast<Mmap2Record*>(record));
     }
   }
   return false;
@@ -1200,8 +1197,7 @@ bool RecordCommand::ProcessJITDebugInfo(const std::vector<JITSymFile>& jit_symfi
 }
 
 template <class RecordType>
-void UpdateMmapRecordForEmbeddedPath(RecordType* record) {
-  RecordType& r = *record;
+void UpdateMmapRecordForEmbeddedPath(RecordType& r, bool has_prot, uint32_t prot) {
   if (r.InKernel()) {
     return;
   }
@@ -1213,7 +1209,7 @@ void UpdateMmapRecordForEmbeddedPath(RecordType* record) {
     filename.resize(filename.size() - 10);
     name_changed = true;
   }
-  if (r.data->pgoff != 0) {
+  if (r.data->pgoff != 0 && (!has_prot || (prot & PROT_EXEC))) {
     // For the case of a shared library "foobar.so" embedded
     // inside an APK, we rewrite the original MMAP from
     // ["path.apk" offset=X] to ["path.apk!/foobar.so" offset=W]
@@ -1247,9 +1243,10 @@ void UpdateMmapRecordForEmbeddedPath(RecordType* record) {
 
 void RecordCommand::UpdateRecordForEmbeddedPath(Record* record) {
   if (record->type() == PERF_RECORD_MMAP) {
-    UpdateMmapRecordForEmbeddedPath(static_cast<MmapRecord*>(record));
+    UpdateMmapRecordForEmbeddedPath(*static_cast<MmapRecord*>(record), false, 0);
   } else if (record->type() == PERF_RECORD_MMAP2) {
-    UpdateMmapRecordForEmbeddedPath(static_cast<Mmap2Record*>(record));
+    auto r = static_cast<Mmap2Record*>(record);
+    UpdateMmapRecordForEmbeddedPath(*r, true, r->data->prot);
   }
 }