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Overhaul MallocSizeOf and related things.

Browse source 
This patch makes the MallocSizeOf stuff in Stylo work more like the HeapSizeOf
stuff already in Servo, except better. In particular, it adds deriving support
for MallocSizeOf, which will make it easier to improve coverage.

The patch does the following.

- Combines servo/components/style/stylesheets/memory.rs and the heapsize crate
  into a new crate, malloc_size_of.

- Forks the heapsize_derive crate, calling it malloc_size_of, so that
  MallocSizeOf can be derived.

- Both the new crates have MIT/Apache licenses, like heapsize, in case they are
  incorporated into heapsize in the future.

- Renames the methods within MallocSizeOf and the related traits so they are
  more concise.

- Removes MallocSizeOfWithGuard.

- Adds `derive(MallocSizeOf)` to a lot of types, in some cases replacing an
  equivalent or almost-equivalent hand-written implementation.

- Adds stuff so that Rc/Arc can be handled properly.
This commit is contained in:
Nicholas Nethercote 2017-09-12 12:03:01 +10:00
parent 24b2d8d9cf
commit 32548e5312
44 changed files with 1188 additions and 486 deletions
Download patch file Download diff file Expand all files Collapse all files

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[package]
name = "malloc_size_of"
version = "0.0.1"
authors = ["The Servo Project Developers"]
license = "MIT/Apache-2.0"
publish = false
[lib]
path = "lib.rs"
[dependencies]
hashglobe = { path = "../hashglobe" }
servo_arc = { path = "../servo_arc" }
smallbitvec = "1.0.3"
smallvec = "0.4"

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// Copyright 2016-2017 The Servo Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! A crate for measuring the heap usage of data structures in a way that
//! integrates with Firefox's memory reporting, particularly the use of
//! mozjemalloc and DMD.
//!
//! This crate has a lot of overlap with the existing `heapsize` crate, and may
//! one day be merged into it. But for now, `heapsize` has the following
//! major shortcomings.
//! - It basically assumes that the `HeapSizeOf` trait can be used for every
//! type, which is not true. Sometimes more than a single size measurement
//! needs to be returned for a type, and sometimes additional synchronization
//! arguments (such as lock guards) need to be passed in.
//! - It has no proper way of measuring some common types, such as `HashSet`
//! and `HashMap`, that don't expose internal pointers.
//! - It has no proper way of handling values with multiple referents, such as
//! `Rc` and `Arc`.
//!
//! This crate solves those problems.
//! - It provides traits for both "shallow" and "deep" measurement, which gives
//! more flexibility in the cases where the traits can't be used.
//! - It allows for measuring blocks even when only an interior pointer can be
//! obtained for heap allocations, e.g. `HashSet` and `HashMap`. (This relies
//! on the heap allocator having suitable support, which mozjemalloc has.)
//! - It allows handling of types like `Rc` and `Arc` by providing special
//! traits that are different to the ones for non-graph structures.
//!
//! Suggested uses are as follows.
//! - When possible, use the `MallocSizeOf` trait. (Deriving support is
//! provided by the `malloc_size_of_derive` crate.)
//! - If you need an additional synchronization argument, provide a function
//! that is like the standard trait method, but with the extra argument.
//! - If you need multiple measurements for a type, provide a function named
//! `add_size_of_children` that takes a mutable reference to a struct that
//! contains the multiple measurement fields.
//! - When deep measurement (via `MallocSizeOf`) cannot be implemented for a
//! type, shallow measurement (via `MallocShallowSizeOf`) in combination with
//! iteration can be a useful substitute.
//! - `Rc` and `Arc` are always tricky, which is why `MallocSizeOf` is not (and
//! should not be) implemented for them.
//! - If an `Rc` or `Arc` is known to be a "primary" reference and can always
//! be measured, it should be measured via the `MallocUnconditionalSizeOf`
//! trait.
//! - If an `Rc` or `Arc` should be measured only if it hasn't been seen
//! before, it should be measured via the `MallocConditionalSizeOf` trait.
//! - Using universal function call syntax is a good idea when measuring boxed
//! fields in structs, because it makes it clear that the Box is being
//! measured as well as the thing it points to. E.g.
//! `<Box<_> as MallocSizeOf>::size_of(field, ops)`.
extern crate hashglobe;
extern crate servo_arc;
extern crate smallbitvec;
extern crate smallvec;
use hashglobe::hash_map::HashMap;
use servo_arc::Arc;
use smallbitvec::SmallBitVec;
use smallvec::{Array, SmallVec};
use std::collections::HashSet;
use std::hash::{BuildHasher, Hash};
use std::os::raw::c_void;
/// A C function that takes a pointer to a heap allocation and returns its size.
type VoidPtrToSizeFn = unsafe extern "C" fn(ptr: *const c_void) -> usize;
/// A closure implementing a stateful predicate on pointers.
type VoidPtrToBoolFnMut = FnMut(*const c_void) -> bool;
/// Operations used when measuring heap usage of data structures.
pub struct MallocSizeOfOps {
/// A function that returns the size of a heap allocation.
size_of_op: VoidPtrToSizeFn,
/// Like `size_of_op`, but can take an interior pointer. Optional, because
/// many places don't need it.
enclosing_size_of_op: Option<VoidPtrToSizeFn>,
/// Check if a pointer has been seen before, and remember it for next time.
/// Useful when measuring `Rc`s and `Arc`s. Optional, because many places
/// don't need it.
have_seen_ptr_op: Option<Box<VoidPtrToBoolFnMut>>,
}
impl MallocSizeOfOps {
pub fn new(size_of: VoidPtrToSizeFn,
malloc_enclosing_size_of: Option<VoidPtrToSizeFn>,
have_seen_ptr: Option<Box<VoidPtrToBoolFnMut>>) -> Self {
MallocSizeOfOps {
size_of_op: size_of,
enclosing_size_of_op: malloc_enclosing_size_of,
have_seen_ptr_op: have_seen_ptr,
}
}
/// Check if an allocation is empty. This relies on knowledge of how Rust
/// handles empty allocations, which may change in the future.
fn is_empty<T>(ptr: *const T) -> bool {
return ptr as usize <= ::std::mem::align_of::<T>();
}
/// Call `size_of_op` on `ptr`, first checking that the allocation isn't
/// empty, because some types (such as `Vec`) utilize empty allocations.
pub fn malloc_size_of<T>(&self, ptr: *const T) -> usize {
if MallocSizeOfOps::is_empty(ptr) {
0
} else {
unsafe { (self.size_of_op)(ptr as *const c_void) }
}
}
/// Call `enclosing_size_of_op` on `ptr`, which must not be empty.
pub fn malloc_enclosing_size_of<T>(&self, ptr: *const T) -> usize {
assert!(!MallocSizeOfOps::is_empty(ptr));
let enclosing_size_of_op = self.enclosing_size_of_op.expect("missing enclosing_size_of_op");
unsafe { enclosing_size_of_op(ptr as *const c_void) }
}
/// Call `have_seen_ptr_op` on `ptr`.
pub fn have_seen_ptr<T>(&mut self, ptr: *const T) -> bool {
let have_seen_ptr_op = self.have_seen_ptr_op.as_mut().expect("missing have_seen_ptr_op");
have_seen_ptr_op(ptr as *const c_void)
}
}
/// Trait for measuring the "deep" heap usage of a data structure. This is the
/// most commonly-used of the traits.
pub trait MallocSizeOf {
/// Measure the heap usage of all descendant heap-allocated structures, but
/// not the space taken up by the value itself.
fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize;
}
/// Trait for measuring the "shallow" heap usage of a container.
pub trait MallocShallowSizeOf {
/// Measure the heap usage of direct descendant structures, but not the
/// space taken up by the value itself. Anything pointed to by the
/// immediate children must be measured separately, using iteration.
fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize;
}
/// Like `MallocSizeOf`, but with a different name so it cannot be used
/// accidentally with derive(MallocSizeOf). For use with types like `Rc` and
/// `Arc` when appropriate (e.g. when measuring a "primary" reference).
pub trait MallocUnconditionalSizeOf {
/// Measure the heap usage of all heap-allocated descendant structures, but
/// not the space taken up by the value itself.
fn unconditional_size_of(&self, ops: &mut MallocSizeOfOps) -> usize;
}
/// Like `MallocSizeOf`, but only measures if the value hasn't already been
/// measured. For use with types like `Rc` and `Arc` when appropriate (e.g.
/// when there is no "primary" reference).
pub trait MallocConditionalSizeOf {
/// Measure the heap usage of all heap-allocated descendant structures, but
/// not the space taken up by the value itself, and only if that heap usage
/// hasn't already been measured.
fn conditional_size_of(&self, ops: &mut MallocSizeOfOps) -> usize;
}
impl<T> MallocShallowSizeOf for Box<T> {
fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
ops.malloc_size_of(&**self)
}
}
impl<T: MallocSizeOf> MallocSizeOf for Box<T> {
fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
self.shallow_size_of(ops) + (**self).size_of(ops)
}
}
impl<A: MallocSizeOf, B: MallocSizeOf> MallocSizeOf for (A, B) {
fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
self.0.size_of(ops) + self.1.size_of(ops)
}
}
impl<T: MallocSizeOf> MallocSizeOf for Option<T> {
fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
if let Some(val) = self.as_ref() {
val.size_of(ops)
} else {
0
}
}
}
impl<T> MallocShallowSizeOf for Vec<T> {
fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
ops.malloc_size_of(self.as_ptr())
}
}
impl<T: MallocSizeOf> MallocSizeOf for Vec<T> {
fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
let mut n = self.shallow_size_of(ops);
for elem in self.iter() {
n += elem.size_of(ops);
}
n
}
}
impl<A: Array> MallocShallowSizeOf for SmallVec<A> {
fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
if self.spilled() {
ops.malloc_size_of(self.as_ptr())
} else {
0
}
}
}
impl<A> MallocSizeOf for SmallVec<A>
where A: Array,
A::Item: MallocSizeOf
{
fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
let mut n = self.shallow_size_of(ops);
for elem in self.iter() {
n += elem.size_of(ops);
}
n
}
}
impl<T, S> MallocShallowSizeOf for HashSet<T, S>
where T: Eq + Hash,
S: BuildHasher
{
fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
// The first value from the iterator gives us an interior pointer.
// `ops.malloc_enclosing_size_of()` then gives us the storage size.
// This assumes that the `HashSet`'s contents (values and hashes) are
// all stored in a single contiguous heap allocation.
self.iter().next().map_or(0, |t| ops.malloc_enclosing_size_of(t))
}
}
impl<T, S> MallocSizeOf for HashSet<T, S>
where T: Eq + Hash + MallocSizeOf,
S: BuildHasher,
{
fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
let mut n = self.shallow_size_of(ops);
for t in self.iter() {
n += t.size_of(ops);
}
n
}
}
impl<K, V, S> MallocShallowSizeOf for HashMap<K, V, S>
where K: Eq + Hash,
S: BuildHasher
{
fn shallow_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
// The first value from the iterator gives us an interior pointer.
// `ops.malloc_enclosing_size_of()` then gives us the storage size.
// This assumes that the `HashMap`'s contents (keys, values, and
// hashes) are all stored in a single contiguous heap allocation.
self.values().next().map_or(0, |v| ops.malloc_enclosing_size_of(v))
}
}
impl<K, V, S> MallocSizeOf for HashMap<K, V, S>
where K: Eq + Hash + MallocSizeOf,
V: MallocSizeOf,
S: BuildHasher,
{
fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
let mut n = self.shallow_size_of(ops);
for (k, v) in self.iter() {
n += k.size_of(ops);
n += v.size_of(ops);
}
n
}
}
// XXX: we don't want MallocSizeOf to be defined for Rc and Arc. If negative
// trait bounds are ever allowed, this code should be uncommented.
// (We do have a compile-fail test for this:
// rc_arc_must_not_derive_malloc_size_of.rs)
//impl<T> !MallocSizeOf for Arc<T> { }
//impl<T> !MallocShallowSizeOf for Arc<T> { }
impl<T: MallocSizeOf> MallocUnconditionalSizeOf for Arc<T> {
fn unconditional_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
ops.malloc_size_of(self.heap_ptr()) + (**self).size_of(ops)
}
}
impl<T: MallocSizeOf> MallocConditionalSizeOf for Arc<T> {
fn conditional_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
if ops.have_seen_ptr(self.heap_ptr()) {
0
} else {
self.unconditional_size_of(ops)
}
}
}
/// For use on types where size_of() returns 0.
#[macro_export]
macro_rules! size_of_is_0(
($($ty:ty),+) => (
$(
impl $crate::MallocSizeOf for $ty {
#[inline(always)]
fn size_of(&self, _: &mut $crate::MallocSizeOfOps) -> usize {
0
}
}
)+
);
($($ty:ident<$($gen:ident),+>),+) => (
$(
impl<$($gen: $crate::MallocSizeOf),+> $crate::MallocSizeOf for $ty<$($gen),+> {
#[inline(always)]
fn size_of(&self, _: &mut $crate::MallocSizeOfOps) -> usize {
0
}
}
)+
);
);
size_of_is_0!(char, str);
size_of_is_0!(u8, u16, u32, u64, usize);
size_of_is_0!(i8, i16, i32, i64, isize);
size_of_is_0!(bool, f32, f64);
// XXX: once we upgrade smallbitvec to 1.0.4, use the new heap_ptr() method to
// implement this properly
size_of_is_0!(SmallBitVec);