Refactor common infrastructure for creating memory reports. (#36579)

This removes a bunch of duplicated code needed to support
ConditionalMallocSizeOf correctly, and fixes multiple places where that
code was subtly wrong (the seen pointers hashset was never cleared).

Testing: Measuring https://www.nist.gov/image-gallery lots of times.

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

components/shared/net/image_cache.rs

@@ -8,6 +8,7 @@ use base::id::PipelineId;
 use compositing_traits::CrossProcessCompositorApi;
 use ipc_channel::ipc::IpcSender;
 use log::debug;
+use malloc_size_of::MallocSizeOfOps;
 use malloc_size_of_derive::MallocSizeOf;
 use pixels::{Image, ImageMetadata};
 use profile_traits::mem::Report;
@@ -116,7 +117,7 @@ pub trait ImageCache: Sync + Send {
     where
         Self: Sized;
 
-    fn memory_report(&self, prefix: &str) -> Report;
+    fn memory_report(&self, prefix: &str, ops: &mut MallocSizeOfOps) -> Report;
 
     /// Definitively check whether there is a cached, fully loaded image available.
     fn get_image(

components/shared/profile/Cargo.toml

@@ -22,6 +22,7 @@ log = { workspace = true }
 malloc_size_of = { workspace = true }
 malloc_size_of_derive = { workspace = true }
 serde = { workspace = true }
+servo_allocator = { path = "../../allocator" }
 servo_config = { path = "../../config" }
 signpost = { git = "https://github.com/pcwalton/signpost.git" }
 strum_macros = { workspace = true }

components/shared/profile/mem.rs

@@ -6,12 +6,16 @@
 
 #![deny(missing_docs)]
 
+use std::cell::{LazyCell, RefCell};
+use std::collections::HashSet;
+use std::ffi::c_void;
 use std::marker::Send;
 
 use crossbeam_channel::Sender;
 use ipc_channel::ipc::{self, IpcSender};
 use ipc_channel::router::ROUTER;
 use log::warn;
+use malloc_size_of::MallocSizeOfOps;
 use serde::{Deserialize, Serialize};
 
 /// A trait to abstract away the various kinds of message senders we use.
@@ -266,3 +270,21 @@ pub enum ProfilerMsg {
     /// Triggers sending back the memory profiling metrics,
     Report(IpcSender<MemoryReportResult>),
 }
+
+thread_local!(static SEEN_POINTERS: LazyCell<RefCell<HashSet<*const c_void>>> = const {
+    LazyCell::new(Default::default)
+});
+
+/// Invoke the provided function after initializing the memory profile tools.
+/// 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,
+        None,
+        Some(Box::new(seen_pointer)),
+    );
+    f(&mut ops);
+}

components/shared/script_layout/lib.rs

@@ -27,6 +27,7 @@ use fonts::{FontContext, SystemFontServiceProxy};
 use fxhash::FxHashMap;
 use ipc_channel::ipc::IpcSender;
 use libc::c_void;
+use malloc_size_of::MallocSizeOfOps;
 use malloc_size_of_derive::MallocSizeOf;
 use net_traits::image_cache::{ImageCache, PendingImageId};
 use pixels::Image;
@@ -217,7 +218,7 @@ pub trait Layout {
 
     /// Requests that layout measure its memory usage. The resulting reports are sent back
     /// via the supplied channel.
-    fn collect_reports(&self, reports: &mut Vec<Report>);
+    fn collect_reports(&self, reports: &mut Vec<Report>, ops: &mut MallocSizeOfOps);
 
     /// Sets quirks mode for the document, causing the quirks mode stylesheet to be used.
     fn set_quirks_mode(&mut self, quirks_mode: QuirksMode);