commit 2eb99af37475ff8ff2b4757ff0fdebc5a821a9da
parent 6f863d55e907da4b6c612941a8939dad9f9840e0
Author: Paul Bone <paul@bone.id.au>
Date: Thu, 16 Oct 2025 22:26:50 +0000
Bug 1984011 - pt 8. Simplify the arena_t constructor r=glandium
Use more:
* initialisers in the class definition,
* initialiser lists in the constructor and
* default constructors for class members
so that code can be removed from the body of the constructor.
Differential Revision: https://phabricator.services.mozilla.com/D263511
Diffstat:
1 file changed, 29 insertions(+), 59 deletions(-)
diff --git a/memory/build/mozjemalloc.cpp b/memory/build/mozjemalloc.cpp
@@ -223,18 +223,18 @@ MOZ_CONSTINIT StaticMutex gInitLock MOZ_UNANNOTATED;
struct arena_stats_t {
// Number of bytes currently mapped.
- size_t mapped;
+ size_t mapped = 0;
// Current number of committed pages (non madvised/decommitted)
- size_t committed;
+ size_t committed = 0;
// Per-size-category statistics.
- size_t allocated_small;
+ size_t allocated_small = 0;
- size_t allocated_large;
+ size_t allocated_large = 0;
// The number of "memory operations" aka mallocs/frees.
- uint64_t operations;
+ uint64_t operations = 0;
};
// Describe size classes to which allocations are rounded up to.
@@ -473,8 +473,8 @@ enum PurgeCondition { PurgeIfThreshold, PurgeUnconditional };
struct arena_t {
#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
- uint32_t mMagic;
# define ARENA_MAGIC 0x947d3d24
+ uint32_t mMagic = ARENA_MAGIC;
#endif
// Linkage for the tree of arenas by id.
@@ -485,7 +485,7 @@ struct arena_t {
// Arena id, that we keep away from the beginning of the struct so that
// free list pointers in TypedBaseAlloc<arena_t> don't overflow in it,
// and it keeps the value it had after the destructor.
- arena_id_t mId;
+ arena_id_t mId = 0;
// Operations on this arena require that lock be locked. The MaybeMutex
// class will elude locking if the arena is accessed from a single thread
@@ -528,7 +528,7 @@ struct arena_t {
// There is one spare chunk per arena, rather than one spare total, in
// order to avoid interactions between multiple threads that could make
// a single spare inadequate.
- arena_chunk_t* mSpare MOZ_GUARDED_BY(mLock);
+ arena_chunk_t* mSpare MOZ_GUARDED_BY(mLock) = nullptr;
// A per-arena opt-in to randomize the offset of small allocations
// Needs no lock, read-only.
@@ -537,8 +537,9 @@ struct arena_t {
// A pseudorandom number generator. Initially null, it gets initialized
// on first use to avoid recursive malloc initialization (e.g. on OSX
// arc4random allocates memory).
- mozilla::non_crypto::XorShift128PlusRNG* mPRNG MOZ_GUARDED_BY(mLock);
- bool mIsPRNGInitializing MOZ_GUARDED_BY(mLock);
+ mozilla::non_crypto::XorShift128PlusRNG* mPRNG MOZ_GUARDED_BY(mLock) =
+ nullptr;
+ bool mIsPRNGInitializing MOZ_GUARDED_BY(mLock) = false;
public:
// Whether this is a private arena. Multiple public arenas are just a
@@ -555,23 +556,23 @@ struct arena_t {
// dirty, and for which madvise(... MADV_FREE) has not been called. By
// tracking this, we can institute a limit on how much dirty unused
// memory is mapped for each arena.
- size_t mNumDirty MOZ_GUARDED_BY(mLock);
+ size_t mNumDirty MOZ_GUARDED_BY(mLock) = 0;
// Precalculated value for faster checks.
size_t mMaxDirty MOZ_GUARDED_BY(mLock);
// The current number of pages that are available without a system call (but
// probably a page fault).
- size_t mNumMAdvised MOZ_GUARDED_BY(mLock);
- size_t mNumFresh MOZ_GUARDED_BY(mLock);
+ size_t mNumMAdvised MOZ_GUARDED_BY(mLock) = 0;
+ size_t mNumFresh MOZ_GUARDED_BY(mLock) = 0;
// Maximum value allowed for mNumDirty.
// Needs no lock, read-only.
size_t mMaxDirtyBase;
// Needs no lock, read-only.
- int32_t mMaxDirtyIncreaseOverride;
- int32_t mMaxDirtyDecreaseOverride;
+ int32_t mMaxDirtyIncreaseOverride = 0;
+ int32_t mMaxDirtyDecreaseOverride = 0;
// The link to gArenas.mOutstandingPurges.
// Note that this must only be accessed while holding gArenas.mPurgeListLock
@@ -595,7 +596,7 @@ struct arena_t {
// completely done. This is used to avoid accessing the list (and list lock)
// on every call to ShouldStartPurge() and to avoid deleting arenas that
// another thread is purging.
- bool mIsPurgePending MOZ_GUARDED_BY(mLock);
+ bool mIsPurgePending MOZ_GUARDED_BY(mLock) = false;
// A mirror of ArenaCollection::mIsDeferredPurgeEnabled, here only to
// optimize memory reads in ShouldStartPurge().
@@ -609,7 +610,7 @@ struct arena_t {
// fixed size area including a null terminating byte. The actual maximum
// length of the string is one less than LABEL_MAX_CAPACITY;
static constexpr size_t LABEL_MAX_CAPACITY = 128;
- char mLabel[LABEL_MAX_CAPACITY];
+ char mLabel[LABEL_MAX_CAPACITY] = {};
private:
// Size/address-ordered tree of this arena's available runs. This tree
@@ -3496,20 +3497,15 @@ void arena_t::operator delete(void* aPtr) {
TypedBaseAlloc<arena_t>::dealloc((arena_t*)aPtr);
}
-arena_t::arena_t(arena_params_t* aParams, bool aIsPrivate) {
- unsigned i;
-
- memset(&mLink, 0, sizeof(mLink));
- memset(&mStats, 0, sizeof(arena_stats_t));
- mId = 0;
-
- // Initialize chunks.
-#ifdef MALLOC_DOUBLE_PURGE
- new (&mChunksMAdvised) DoublyLinkedList<arena_chunk_t>();
-#endif
- mSpare = nullptr;
-
- mRandomizeSmallAllocations = opt_randomize_small;
+arena_t::arena_t(arena_params_t* aParams, bool aIsPrivate)
+ : mRandomizeSmallAllocations(opt_randomize_small),
+ mIsPrivate(aIsPrivate),
+ // The default maximum amount of dirty pages allowed on arenas is a
+ // fraction of opt_dirty_max.
+ mMaxDirtyBase((aParams && aParams->mMaxDirty) ? aParams->mMaxDirty
+ : (opt_dirty_max / 8)),
+ mLastSignificantReuseNS(GetTimestampNS()),
+ mIsDeferredPurgeEnabled(gArenas.IsDeferredPurgeEnabled()) {
MaybeMutex::DoLock doLock = MaybeMutex::MUST_LOCK;
if (aParams) {
uint32_t randFlags = aParams->mFlags & ARENA_FLAG_RANDOMIZE_SMALL_MASK;
@@ -3551,45 +3547,23 @@ arena_t::arena_t(arena_params_t* aParams, bool aIsPrivate) {
strncpy(mLabel, aParams->mLabel, LABEL_MAX_CAPACITY - 1);
mLabel[LABEL_MAX_CAPACITY - 1] = 0;
- // If the string was trucated, then replace it's end with "..."
+ // If the string was truncated, then replace its end with "..."
if (strlen(aParams->mLabel) >= LABEL_MAX_CAPACITY) {
for (int i = 0; i < 3; i++) {
mLabel[LABEL_MAX_CAPACITY - 2 - i] = '.';
}
}
- } else {
- mLabel[0] = 0;
}
- } else {
- mMaxDirtyIncreaseOverride = 0;
- mMaxDirtyDecreaseOverride = 0;
-
- mLabel[0] = 0;
}
- mLastSignificantReuseNS = GetTimestampNS();
- mIsPurgePending = false;
- mIsDeferredPurgeEnabled = gArenas.IsDeferredPurgeEnabled();
-
MOZ_RELEASE_ASSERT(mLock.Init(doLock));
- mPRNG = nullptr;
- mIsPRNGInitializing = false;
-
- mIsPrivate = aIsPrivate;
-
- mNumDirty = 0;
- mNumFresh = 0;
- mNumMAdvised = 0;
- // The default maximum amount of dirty pages allowed on arenas is a fraction
- // of opt_dirty_max.
- mMaxDirtyBase = (aParams && aParams->mMaxDirty) ? aParams->mMaxDirty
- : (opt_dirty_max / 8);
UpdateMaxDirty();
// Initialize bins.
SizeClass sizeClass(1);
+ unsigned i;
for (i = 0;; i++) {
arena_bin_t& bin = mBins[i];
bin.Init(sizeClass);
@@ -3601,10 +3575,6 @@ arena_t::arena_t(arena_params_t* aParams, bool aIsPrivate) {
sizeClass = sizeClass.Next();
}
MOZ_ASSERT(i == NUM_SMALL_CLASSES - 1);
-
-#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
- mMagic = ARENA_MAGIC;
-#endif
}
arena_t::~arena_t() {
