From 42f37f04c53f537de748189b1c74e847bb69e934 Mon Sep 17 00:00:00 2001
From: Yabin Cui <yabinc@google.com>
Date: Fri, 22 Jan 2016 15:38:46 -0800
Subject: [PATCH] Simpleperf: adjust default mmap_pages used when recording.

If running as non-root, there is a limitation on how many
mmap pages can be used for profiling per user. So adjust
default mmap_pages value to fit the limit, and add option
to change it.

Change-Id: Ie73f33c473498689234972989fc55b7731366792
---
 simpleperf/cmd_record.cpp      | 20 +++++++++++++++++---
 simpleperf/cmd_record_test.cpp |  6 ++++++
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/simpleperf/cmd_record.cpp b/simpleperf/cmd_record.cpp
index 45be4f6e..ee738c00 100644
--- a/simpleperf/cmd_record.cpp
+++ b/simpleperf/cmd_record.cpp
@@ -96,6 +96,9 @@ class RecordCommand : public Command {
             "                   k: only when the branch target is in the kernel\n"
             "                 This option requires at least one branch type among any,\n"
             "                 any_call, any_ret, ind_call.\n"
+            "    -m mmap_pages\n"
+            "                 Set the size of the buffer used to receiving sample data from\n"
+            "                 the kernel. It should be a power of 2. The default value is 16.\n"
             "    --no-inherit\n"
             "                 Don't record created child threads/processes.\n"
             "    --no-unwind  If `--call-graph dwarf` option is used, then the user's stack will\n"
@@ -121,7 +124,7 @@ class RecordCommand : public Command {
         unwind_dwarf_callchain_(true),
         post_unwind_(false),
         child_inherit_(true),
-        perf_mmap_pages_(256),
+        perf_mmap_pages_(16),
         record_filename_("perf.data") {
     signaled = false;
     scoped_signal_handler_.reset(
@@ -165,8 +168,8 @@ class RecordCommand : public Command {
   std::vector<EventTypeAndModifier> measured_event_types_;
   EventSelectionSet event_selection_set_;
 
-  // mmap pages used by each perf event file, should be power of 2.
-  const size_t perf_mmap_pages_;
+  // mmap pages used by each perf event file, should be a power of 2.
+  size_t perf_mmap_pages_;
 
   std::unique_ptr<RecordCache> record_cache_;
   ThreadTree thread_tree_;
@@ -367,6 +370,17 @@ bool RecordCommand::ParseOptions(const std::vector<std::string>& args,
         }
         branch_sampling_ |= it->second;
       }
+    } else if (args[i] == "-m") {
+      if (!NextArgumentOrError(args, &i)) {
+        return false;
+      }
+      char* endptr;
+      uint64_t pages = strtoull(args[i].c_str(), &endptr, 0);
+      if (*endptr != '\0' || !IsPowerOfTwo(pages)) {
+        LOG(ERROR) << "Invalid mmap_pages: '" << args[i] << "'";
+        return false;
+      }
+      perf_mmap_pages_ = pages;
     } else if (args[i] == "--no-inherit") {
       child_inherit_ = false;
     } else if (args[i] == "--no-unwind") {
diff --git a/simpleperf/cmd_record_test.cpp b/simpleperf/cmd_record_test.cpp
index 0a9dfde2..ca38a050 100644
--- a/simpleperf/cmd_record_test.cpp
+++ b/simpleperf/cmd_record_test.cpp
@@ -172,3 +172,9 @@ TEST(record_cmd, cpu_option) {
   ASSERT_TRUE(RecordCmd()->Run({"--cpu", "0", "sleep", "1"}));
   ASSERT_TRUE(RecordCmd()->Run({"--cpu", "0", "-a", "sleep", "1"}));
 }
+
+TEST(record_cmd, mmap_page_option) {
+  ASSERT_TRUE(RecordCmd()->Run({"-m", "1", "sleep", "1"}));
+  ASSERT_FALSE(RecordCmd()->Run({"-m", "0", "sleep", "1"}));
+  ASSERT_FALSE(RecordCmd()->Run({"-m", "7", "sleep", "1"}));
+}
-- 
2.11.0