Simpleperf: use OneTimeFreeAllocator to allocate symbol names.

simpleperf report takes a lot of time mallocing and freeing memory.
This change reduces the time to free memory.

Before this change:
$sudo simpleperf stat simpleperf report
Performance counter statistics:

    3,258,481,203  cpu-cycles                # 2.290946 GHz                      (80%)
    4,147,660,154  instructions              # 0.785619 cycles per instruction   (79%)

Total test time: 1.422330 seconds.

After this change:
$sudo simpleperf stat simpleperf report
Performance counter statistics:

   1,699,221,386  cpu-cycles                # 2.994754 GHz                      (79%)
   2,739,945,156  instructions              # 0.620166 cycles per instruction   (81%)

Total test time: 0.567399 seconds.

This change also fix a bug in record_file_test.cpp.

Bug: 23387541

Change-Id: I59fc86ca54a6c09bd08eec8ada931ccff88d3102

1 files changed, 27 insertions, 0 deletions

diff --git a/simpleperf/utils.cpp b/simpleperf/utils.cpp
index bca02bdc..ee95b091 100644
--- a/simpleperf/utils.cpp
+++ b/simpleperf/utils.cpp
@@ -23,8 +23,35 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include <algorithm>
+#include <string>
+
 #include <base/logging.h>
 
+void OneTimeFreeAllocator::Clear() {
+  for (auto& p : v_) {
+    delete[] p;
+  }
+  v_.clear();
+  cur_ = nullptr;
+  end_ = nullptr;
+}
+
+const char* OneTimeFreeAllocator::AllocateString(const std::string& s) {
+  size_t size = s.size() + 1;
+  if (cur_ + size > end_) {
+    size_t alloc_size = std::max(size, unit_size_);
+    char* p = new char[alloc_size];
+    v_.push_back(p);
+    cur_ = p;
+    end_ = p + alloc_size;
+  }
+  strcpy(cur_, s.c_str());
+  const char* result = cur_;
+  cur_ += size;
+  return result;
+}
+
 void PrintIndented(size_t indent, const char* fmt, ...) {
   va_list ap;
   va_start(ap, fmt);