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Optimize symbol lookup

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Do not run symbol lookup on already visited soinfos
 Not taking into account already visited libraries
 dramatically slows down dlsym in cases when there
 are multiple occurrences of a large library in
 dependency tree.

Bug: 16977077

(cherry picked from commit 042426ba6375f5c145379e598486ec6d675533c9)

Change-Id: I69d59e395e8112f119343e8a4d72fe31cd449f31
This commit is contained in:
Dmitriy Ivanov 2014-08-12 21:02:13 -07:00
parent d332bc6878
commit 8a84d383fb
2 changed files with 17 additions and 0 deletions
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9
linker/linked_list.h
View File

@ -100,6 +100,15 @@ class LinkedList {
}
}
bool contains(const T* el) {
for (LinkedListEntry<T>* e = head_; e != nullptr; e = e->next) {
if (e->element != nullptr && e->element == el) {
return true;
}
}
return false;
}
private:
LinkedListEntry<T>* head_;
LinkedListEntry<T>* tail_;

8
linker/linker.cpp
View File

@ -607,17 +607,24 @@ class SoinfoListAllocatorRW {
// specified soinfo object and its dependencies in breadth first order.
ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name, soinfo* caller) {
LinkedList<soinfo, SoinfoListAllocatorRW> visit_list;
LinkedList<soinfo, SoinfoListAllocatorRW> visited;
visit_list.push_back(si);
soinfo* current_soinfo;
while ((current_soinfo = visit_list.pop_front()) != nullptr) {
if (visited.contains(current_soinfo)) {
continue;
}
ElfW(Sym)* result = soinfo_elf_lookup(current_soinfo, elfhash(name), name,
caller == current_soinfo ? SymbolLookupScope::kAllowLocal : SymbolLookupScope::kExcludeLocal);
if (result != nullptr) {
*found = current_soinfo;
visit_list.clear();
visited.clear();
return result;
}
visited.push_back(current_soinfo);
current_soinfo->get_children().for_each([&](soinfo* child) {
visit_list.push_back(child);
@ -625,6 +632,7 @@ ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name, soi
}
visit_list.clear();
visited.clear();
return nullptr;
}