From 9036882d49841883a673a401f932845ccf6361bb Mon Sep 17 00:00:00 2001
From: Yurii Zubrytskyi <zyy@google.com>
Date: Tue, 17 Dec 2024 19:21:16 -0800
Subject: [res] Optimize isUpToDate() for ApkAssets

This is the most called function in the whole Resources
codebase, and it often takes a millisecond+ to just check if
the underlying file still exists.

This CL optimizes several aspects of the function

- knowing that all /data/ paths are writable, return early from
  the isReadonlyFilesystem() without a syscall

- use the same getFileModDate() function for all native classes
  instead of the custom stat-based code

- skip the modification time getter for all readonly filesystems
  when we know that the idmap, overlay and target can't change.

- add some default-disabled logging code to print timings for
  easier performance measurement

Bug: 319137634
Test: build, boot and atest libandroidfw_tests
Flag: EXEMPT performance-critical code that can't have two
      versions
Change-Id: I0f801bef386f202eda775cca9657e2a0b6b55c95
---
 libs/androidfw/Idmap.cpp | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

(limited to 'libs/androidfw/Idmap.cpp')

diff --git a/libs/androidfw/Idmap.cpp b/libs/androidfw/Idmap.cpp
index 3ecd82b074a1..262e7df185b7 100644
--- a/libs/androidfw/Idmap.cpp
+++ b/libs/androidfw/Idmap.cpp
@@ -22,9 +22,10 @@
 #include "android-base/logging.h"
 #include "android-base/stringprintf.h"
 #include "android-base/utf8.h"
-#include "androidfw/misc.h"
+#include "androidfw/AssetManager.h"
 #include "androidfw/ResourceTypes.h"
 #include "androidfw/Util.h"
+#include "androidfw/misc.h"
 #include "utils/ByteOrder.h"
 #include "utils/Trace.h"
 
@@ -268,11 +269,16 @@ LoadedIdmap::LoadedIdmap(const std::string& idmap_path, const Idmap_header* head
       configurations_(configs),
       overlay_entries_(overlay_entries),
       string_pool_(std::move(string_pool)),
-      idmap_fd_(
-          android::base::utf8::open(idmap_path.c_str(), O_RDONLY | O_CLOEXEC | O_BINARY | O_PATH)),
       overlay_apk_path_(overlay_apk_path),
       target_apk_path_(target_apk_path),
-      idmap_last_mod_time_(getFileModDate(idmap_fd_.get())) {
+      idmap_last_mod_time_(kInvalidModDate) {
+  if (!isReadonlyFilesystem(std::string(overlay_apk_path_).c_str()) ||
+      !(target_apk_path_ == AssetManager::TARGET_APK_PATH ||
+        isReadonlyFilesystem(std::string(target_apk_path_).c_str()))) {
+    idmap_fd_.reset(
+        android::base::utf8::open(idmap_path.c_str(), O_RDONLY | O_CLOEXEC | O_BINARY | O_PATH));
+    idmap_last_mod_time_ = getFileModDate(idmap_fd_);
+  }
 }
 
 std::unique_ptr<LoadedIdmap> LoadedIdmap::Load(StringPiece idmap_path, StringPiece idmap_data) {
@@ -381,8 +387,11 @@ std::unique_ptr<LoadedIdmap> LoadedIdmap::Load(StringPiece idmap_path, StringPie
                       overlay_entries, std::move(idmap_string_pool), *overlay_path, *target_path));
 }
 
-bool LoadedIdmap::IsUpToDate() const {
-  return idmap_last_mod_time_ == getFileModDate(idmap_fd_.get());
+UpToDate LoadedIdmap::IsUpToDate() const {
+  if (idmap_last_mod_time_ == kInvalidModDate) {
+    return UpToDate::Always;
+  }
+  return fromBool(idmap_last_mod_time_ == getFileModDate(idmap_fd_.get()));
 }
 
 }  // namespace android
-- 
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