Various memory measurement improvements (#36834)

The two significant changes here are 1) a commit that frees memory used
to perform memory reporting once the reporting is complete, 2) memory
reporting for the system font service. There are various other commits
that remove `#[ignore_malloc_size_of]` attributes for data that we are
now able to measure, but they do not significantly change our
measurements when testing servo.org.

Testing: Comparing the output of about:memory on servo.org.

---------

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

2 files changed, 7 insertions, 2 deletions

diff --git a/components/shared/compositing/lib.rs b/components/shared/compositing/lib.rs
index 31371f87529..2bc2cc74d50 100644
--- a/components/shared/compositing/lib.rs
+++ b/components/shared/compositing/lib.rs
@@ -14,6 +14,7 @@ use embedder_traits::{
 use euclid::Rect;
 use ipc_channel::ipc::IpcSender;
 use log::warn;
+use malloc_size_of_derive::MallocSizeOf;
 use pixels::Image;
 use strum_macros::IntoStaticStr;
 use style_traits::CSSPixel;
@@ -188,7 +189,7 @@ pub struct CompositionPipeline {
 }
 
 /// A mechanism to send messages from ScriptThread to the parent process' WebRender instance.
-#[derive(Clone, Deserialize, Serialize)]
+#[derive(Clone, Deserialize, MallocSizeOf, Serialize)]
 pub struct CrossProcessCompositorApi(pub IpcSender<CompositorMsg>);
 
 impl CrossProcessCompositorApi {
diff --git a/components/shared/profile/mem.rs b/components/shared/profile/mem.rs
index 1be4eb5abc4..b626facd042 100644
--- a/components/shared/profile/mem.rs
+++ b/components/shared/profile/mem.rs
@@ -279,7 +279,6 @@ thread_local!(static SEEN_POINTERS: LazyCell<RefCell<HashSet<*const c_void>>> =
 /// The function is expected to call all the desired [MallocSizeOf::size_of]
 /// for allocations reachable from the current thread.
 pub fn perform_memory_report<F: FnOnce(&mut MallocSizeOfOps)>(f: F) {
-    SEEN_POINTERS.with(|pointers| pointers.borrow_mut().clear());
     let seen_pointer = move |ptr| SEEN_POINTERS.with(|pointers| !pointers.borrow_mut().insert(ptr));
     let mut ops = MallocSizeOfOps::new(
         servo_allocator::usable_size,
@@ -287,4 +286,9 @@ pub fn perform_memory_report<F: FnOnce(&mut MallocSizeOfOps)>(f: F) {
         Some(Box::new(seen_pointer)),
     );
     f(&mut ops);
+    SEEN_POINTERS.with(|pointers| {
+        let mut pointers = pointers.borrow_mut();
+        pointers.clear();
+        pointers.shrink_to_fit();
+    });
 }