commit 2ea6de11962fea5613f15308b202fb505e57ae9b
author Yabin Cui <yabinc@google.com> Mon Oct 24 19:13:09 2016 -0700
committer Yabin Cui <yabinc@google.com> Wed Oct 26 17:08:13 2016 -0700
tree b0e52846150f77724aa8c2e4d6500d06b58b13cd
parent e7448f00cf02ebe92f41881cf9c4b198cadbb8af

simpleperf: merge records from different buffers in memory.

By reading records from all buffers at once, we can merge records
in memory instead of sorting them in perf.data. To make it clear,
this patch only contains the code to merge records in memory, and
I will remove old method later.

Bug: http://b/32343227
Test: run simpleperf_unit_test.
Test: run simpleperf_runtest.py.
Change-Id: Iea2da06c072243c2014f43c8aa6d96a23cfb9123

simpleperf/event_fd.cpp

diff --git a/simpleperf/event_fd.cpp b/simpleperf/event_fd.cpp
index 39df085..e01147b 100644
--- a/simpleperf/event_fd.cpp
+++ b/simpleperf/event_fd.cpp
@@ -37,8 +37,6 @@
 #include "perf_event.h"
 #include "utils.h"
 
-std::vector<char> EventFd::data_process_buffer_;
-
 static int perf_event_open(const perf_event_attr& attr, pid_t pid, int cpu,
                            int group_fd, unsigned long flags) {  // NOLINT
   return syscall(__NR_perf_event_open, &attr, pid, cpu, group_fd, flags);
@@ -157,9 +155,6 @@
   mmap_metadata_page_ = reinterpret_cast<perf_event_mmap_page*>(mmap_addr_);
   mmap_data_buffer_ = reinterpret_cast<char*>(mmap_addr_) + page_size;
   mmap_data_buffer_size_ = mmap_len_ - page_size;
-  if (data_process_buffer_.size() < mmap_data_buffer_size_) {
-    data_process_buffer_.resize(mmap_data_buffer_size_);
-  }
   return true;
 }
 
@@ -189,7 +184,7 @@
   }
 }
 
-size_t EventFd::GetAvailableMmapData(const char** pdata) {
+size_t EventFd::GetAvailableMmapData(std::vector<char>& buffer, size_t& buffer_pos) {
   if (!HasMappedBuffer()) {
     return 0;
   }
@@ -216,18 +211,27 @@
     // No available data.
     return 0;
   }
+  size_t read_bytes;
+  if (read_head < write_head) {
+    read_bytes = write_head - read_head;
+  } else {
+    read_bytes = mmap_data_buffer_size_ - read_head + write_head;
+  }
+  // Extend the buffer if it is not big enough.
+  if (buffer.size() < buffer_pos + read_bytes) {
+    buffer.resize(buffer_pos + read_bytes);
+  }
 
   // Make sure we can see the data after the fence.
   std::atomic_thread_fence(std::memory_order_acquire);
 
-  // Copy records from mapped buffer to data_process_buffer. Note that records
-  // can be wrapped at the end of the mapped buffer.
-  char* to = data_process_buffer_.data();
+  // Copy records from mapped buffer. Note that records can be wrapped at the
+  // end of the mapped buffer.
+  char* to = &buffer[buffer_pos];
   if (read_head < write_head) {
     char* from = mmap_data_buffer_ + read_head;
     size_t n = write_head - read_head;
     memcpy(to, from, n);
-    to += n;
   } else {
     char* from = mmap_data_buffer_ + read_head;
     size_t n = mmap_data_buffer_size_ - read_head;
@@ -236,10 +240,8 @@
     from = mmap_data_buffer_;
     n = write_head;
     memcpy(to, from, n);
-    to += n;
   }
-  size_t read_bytes = to - data_process_buffer_.data();
-  *pdata = data_process_buffer_.data();
+  buffer_pos += read_bytes;
   DiscardMmapData(read_bytes);
   return read_bytes;
 }