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_utils.h b/linker/linker_utils.h
index 34a597b..5073b10 100644
--- a/linker/linker_utils.h
+++ b/linker/linker_utils.h
@@ -47,6 +47,9 @@
// normalizes entry name by calling normalize_path function.
void resolve_paths(std::vector<std::string>& paths,
std::vector<std::string>* resolved_paths);
+// Resolve a single path. Return empty string when the path is invalid or can't
+// be resolved.
+std::string resolve_path(const std::string& path);
void split_path(const char* path, const char* delimiters, std::vector<std::string>* paths);