Don't resolve already resolved paths when parsing ld.config.txt
When parsing ld.config.txt, paths in *.search.paths properties are
resolved using resolved_paths(). This is causing a number of newfstatat
system calls during a process start-up and is contributing about 3.6%
of the entire linker initialization time.
Optimize the overhead by not resolving already resolved paths; resolved
paths are cached.
Bug: 132348336
Test: strace -C -e newfstatat ls shows the number of the syscalls is
reduced from 131 to 99
Test: simpleperf record --call-graph fp -f 10000000 -o /data/perf.data ls
simpleperf report -g -i /data/perf.data
shows percentage of get_paths() from 2.9% to 2.5%
Change-Id: I79823255a89f6e2a63b80c74e6768850276ab536
diff --git a/linker/linker_config.cpp b/linker/linker_config.cpp
index 7741904..46c91a3 100644
--- a/linker/linker_config.cpp
+++ b/linker/linker_config.cpp
@@ -417,9 +417,22 @@
if (resolve) {
std::vector<std::string> resolved_paths;
-
- // do not remove paths that do not exist
- resolve_paths(paths, &resolved_paths);
+ for (const auto& path : paths) {
+ if (path.empty()) {
+ continue;
+ }
+ // this is single threaded. no need to lock
+ auto cached = resolved_paths_.find(path);
+ if (cached == resolved_paths_.end()) {
+ resolved_paths_[path] = resolve_path(path);
+ cached = resolved_paths_.find(path);
+ }
+ CHECK(cached != resolved_paths_.end());
+ if (cached->second.empty()) {
+ continue;
+ }
+ resolved_paths.push_back(cached->second);
+ }
return resolved_paths;
} else {
@@ -442,6 +455,7 @@
return it;
}
std::unordered_map<std::string, PropertyValue> properties_;
+ std::unordered_map<std::string, std::string> resolved_paths_;
int target_sdk_version_;
DISALLOW_IMPLICIT_CONSTRUCTORS(Properties);