net: Remove 70KB of relocatable string pointers.

Profiling shows that effective_tld_names.cc generates more than 70 KB of
tables containing constant pointers to strings. On Linux and Android, this
makes the tables relocatable, which means:

- The tables are placed in the non-shareable RELRO section of the
  ELF library. On Android, each Chromium process will require 70 KB
  of private RAM to store them.

- The pointers need to be relocated by the dynamic linker at load time,
  slowing down startup time (mainly due to the extra page faults,
  especially during a cold boot).

This patch removes these pointers by generating tables that only
contain offsets into a common string pool, using the gperf -P option
and modifying the caller of the generated function to perform the
relocation at runtime.

On Android, this patch should save a little RAM in each Chromium
process. It will also slightly speed up startup / library loading.

BUG=249747,245442
R=nyquist@chromium.org, pam@chromium.org

Review URL: https://codereview.chromium.org/18341004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@210990 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 14 insertions, 15 deletions

diff --git a/net/tools/tld_cleanup/README b/net/tools/tld_cleanup/README
index ac563cc..a7f137d 100644
--- a/net/tools/tld_cleanup/README
+++ b/net/tools/tld_cleanup/README
@@ -22,7 +22,7 @@ When updating src/net/base/registry_controlled_domains/effective_tld_names.dat:
 
 6. Run gperf on the new effective_tld_names.gperf:
      pushd src/net/base/registry_controlled_domains;
-     gperf -a -L "C++" -C -c -o -t -k '*' -NFindDomain -D -m 10 \
+     gperf -a -L "C++" -C -c -o -t -k '*' -NFindDomain -P -K name_offset -D -m 10 \
          effective_tld_names.gperf > effective_tld_names.cc;
      popd;
    It will produce a new effective_tld_names.cc.
diff --git a/net/tools/tld_cleanup/tld_cleanup_util.cc b/net/tools/tld_cleanup/tld_cleanup_util.cc
index 9cda566..efdc99b 100644
--- a/net/tools/tld_cleanup/tld_cleanup_util.cc
+++ b/net/tools/tld_cleanup/tld_cleanup_util.cc
@@ -29,20 +29,19 @@ namespace tld_cleanup {
 // been created with write access.
 bool WriteRules(const RuleMap& rules, const base::FilePath& outfile) {
   std::string data;
-  data.append(
-"%{\n"
-"// Copyright 2012 The Chromium Authors. All rights reserved.\n"
-"// Use of this source code is governed by a BSD-style license that can be\n"
-"// found in the LICENSE file.\n\n"
-"// This file is generated by net/tools/tld_cleanup/.\n"
-"// DO NOT MANUALLY EDIT!\n"
-"%}\n"
-"struct DomainRule {\n"
-"  const char *name;\n"
-"  int type;  // flags: 1: exception, 2: wildcard, 4: private\n"
-"};\n"
-"%%\n"
-  );
+  data.append("%{\n"
+              "// Copyright 2012 The Chromium Authors. All rights reserved.\n"
+              "// Use of this source code is governed by a BSD-style license "
+              "that can be\n"
+              "// found in the LICENSE file.\n\n"
+              "// This file is generated by net/tools/tld_cleanup/.\n"
+              "// DO NOT MANUALLY EDIT!\n"
+              "%}\n"
+              "struct DomainRule {\n"
+              "  int name_offset;\n"
+              "  int type;  // flags: 1: exception, 2: wildcard, 4: private\n"
+              "};\n"
+              "%%\n");
 
   for (RuleMap::const_iterator i = rules.begin(); i != rules.end(); ++i) {
     data.append(i->first);