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Profiler: Cache and reuse mapped ELF objects

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In multi-process profiles, the same ELF objects tend to occur many
times (everyone has libc.so for example) so we will quickly run out
of VM if we map each object once per process that uses it.

Fix this by adding a "mapped object cache" that maps the path of
an ELF object to a cached memory mapping and wrapping ELF::Image.
This commit is contained in:
Andreas Kling 2021-03-03 21:17:32 +01:00
parent faed0e63dc
commit 0fc3983c8d
3 changed files with 44 additions and 13 deletions
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45
Userland/DevTools/Profiler/Profile.cpp
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@ -316,7 +316,11 @@ Result<NonnullOwnPtr<Profile>, String> Profile::load_from_perfcore_file(const St
library_metadata = it->library_metadata.ptr();
if (auto* library = library_metadata ? library_metadata->library_containing(ptr) : nullptr) {
object_name = library->name;
symbol = library->elf.symbolicate(ptr - library->base, &offset);
if (library->object) {
symbol = library->object->elf.symbolicate(ptr - library->base, &offset);
} else {
symbol = "??";
}
} else {
symbol = "??";
}
@ -401,6 +405,32 @@ GUI::Model* Profile::disassembly_model()
return m_disassembly_model;
}
HashMap<String, OwnPtr<MappedObject>> g_mapped_object_cache;
static MappedObject* get_or_create_mapped_object(const String& path)
{
if (auto it = g_mapped_object_cache.find(path); it != g_mapped_object_cache.end())
return it->value.ptr();
auto file_or_error = MappedFile::map(path);
if (file_or_error.is_error()) {
g_mapped_object_cache.set(path, {});
return nullptr;
}
auto elf = ELF::Image(file_or_error.value()->bytes());
if (!elf.is_valid()) {
g_mapped_object_cache.set(path, {});
return nullptr;
}
auto new_mapped_object = adopt_own(*new MappedObject {
.file = file_or_error.release_value(),
.elf = move(elf),
});
auto* ptr = new_mapped_object.ptr();
g_mapped_object_cache.set(path, move(new_mapped_object));
return ptr;
}
LibraryMetadata::LibraryMetadata(JsonArray regions)
: m_regions(move(regions))
{
@ -421,16 +451,11 @@ LibraryMetadata::LibraryMetadata(JsonArray regions)
if (name.contains(".so"))
path = String::formatted("/usr/lib/{}", path);
auto file_or_error = MappedFile::map(path);
if (file_or_error.is_error()) {
m_libraries.set(name, {});
auto* mapped_object = get_or_create_mapped_object(path);
if (!mapped_object)
continue;
}
auto elf = ELF::Image(file_or_error.value()->bytes());
if (!elf.is_valid())
continue;
auto library = adopt_own(*new Library { base, size, name, file_or_error.release_value(), move(elf) });
m_libraries.set(name, move(library));
m_libraries.set(name, adopt_own(*new Library { base, size, name, mapped_object }));
}
}