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Bug 1414155 - Factor out size classes logic for tiny, quantum and sub-page classes. r=njn
We create a new helper class that rounds up allocations sizes and categorizes them. Compilers are smart enough to elide what they don't need, like in malloc_good_size, they elide the code related to the class type enum. --HG-- extra : rebase_source : 61381e600587b045e720a85a7b46673edeb691b9
This commit is contained in:
Mike Hommey
parent
161c7d7841
commit
1c4a4f48fa
@ -574,6 +574,50 @@ struct ExtentTreeBoundsTrait : public ExtentTreeTrait
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}
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};
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// Describe size classes to which allocations are rounded up to.
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// TODO: add large and huge types when the arena allocation code
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// changes in a way that allows it to be beneficial.
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class SizeClass
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{
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public:
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enum ClassType
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{
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Tiny,
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Quantum,
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SubPage,
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};
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explicit inline SizeClass(size_t aSize)
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{
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if (aSize < small_min) {
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mType = Tiny;
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mSize = std::max(RoundUpPow2(aSize), size_t(1U << TINY_MIN_2POW));
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} else if (aSize <= small_max) {
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mType = Quantum;
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mSize = QUANTUM_CEILING(aSize);
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} else if (aSize <= bin_maxclass) {
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mType = SubPage;
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mSize = RoundUpPow2(aSize);
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} else {
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MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Invalid size");
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}
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}
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SizeClass& operator=(const SizeClass& aOther) = default;
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bool operator==(const SizeClass& aOther) { return aOther.mSize == mSize; }
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size_t Size() { return mSize; }
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ClassType Type() { return mType; }
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SizeClass Next() { return SizeClass(mSize + 1); }
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private:
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ClassType mType;
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size_t mSize;
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};
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// ***************************************************************************
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// Radix tree data structures.
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//
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@ -2984,23 +3028,22 @@ arena_t::MallocSmall(size_t aSize, bool aZero)
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void* ret;
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arena_bin_t* bin;
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arena_run_t* run;
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SizeClass sizeClass(aSize);
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aSize = sizeClass.Size();
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if (aSize < small_min) {
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// Tiny.
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aSize = RoundUpPow2(aSize);
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if (aSize < (1U << TINY_MIN_2POW)) {
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aSize = 1U << TINY_MIN_2POW;
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}
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bin = &mBins[FloorLog2(aSize >> TINY_MIN_2POW)];
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} else if (aSize <= small_max) {
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// Quantum-spaced.
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aSize = QUANTUM_CEILING(aSize);
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bin = &mBins[ntbins + (aSize >> QUANTUM_2POW_MIN) - 1];
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} else {
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// Sub-page.
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aSize = RoundUpPow2(aSize);
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bin = &mBins[ntbins + nqbins +
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(FloorLog2(aSize >> SMALL_MAX_2POW_DEFAULT) - 1)];
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switch (sizeClass.Type()) {
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case SizeClass::Tiny:
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bin = &mBins[FloorLog2(aSize >> TINY_MIN_2POW)];
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break;
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case SizeClass::Quantum:
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bin = &mBins[ntbins + (aSize >> QUANTUM_2POW_MIN) - 1];
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break;
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case SizeClass::SubPage:
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bin = &mBins[ntbins + nqbins +
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(FloorLog2(aSize >> SMALL_MAX_2POW_DEFAULT) - 1)];
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break;
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default:
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MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Unexpected size class type");
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}
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MOZ_DIAGNOSTIC_ASSERT(aSize == bin->mSizeClass);
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@ -3686,22 +3729,15 @@ arena_ralloc(void* aPtr, size_t aSize, size_t aOldSize, arena_t* aArena)
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size_t copysize;
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// Try to avoid moving the allocation.
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if (aSize < small_min) {
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if (aOldSize < small_min &&
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(RoundUpPow2(aSize) >> (TINY_MIN_2POW + 1) ==
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RoundUpPow2(aOldSize) >> (TINY_MIN_2POW + 1))) {
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goto IN_PLACE; // Same size class.
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}
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} else if (aSize <= small_max) {
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if (aOldSize >= small_min && aOldSize <= small_max &&
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(QUANTUM_CEILING(aSize) >> QUANTUM_2POW_MIN) ==
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(QUANTUM_CEILING(aOldSize) >> QUANTUM_2POW_MIN)) {
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goto IN_PLACE; // Same size class.
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}
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} else if (aSize <= bin_maxclass) {
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if (aOldSize > small_max && aOldSize <= bin_maxclass &&
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RoundUpPow2(aSize) == RoundUpPow2(aOldSize)) {
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goto IN_PLACE; // Same size class.
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if (aSize <= bin_maxclass) {
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if (aOldSize <= bin_maxclass && SizeClass(aSize) == SizeClass(aOldSize)) {
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if (aSize < aOldSize) {
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memset(
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(void*)(uintptr_t(aPtr) + aSize), kAllocPoison, aOldSize - aSize);
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} else if (opt_zero && aSize > aOldSize) {
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memset((void*)(uintptr_t(aPtr) + aOldSize), 0, aSize - aOldSize);
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}
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return aPtr;
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}
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} else if (aOldSize > bin_maxclass && aOldSize <= arena_maxclass) {
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MOZ_ASSERT(aSize > bin_maxclass);
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@ -3731,13 +3767,6 @@ arena_ralloc(void* aPtr, size_t aSize, size_t aOldSize, arena_t* aArena)
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}
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idalloc(aPtr);
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return ret;
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IN_PLACE:
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if (aSize < aOldSize) {
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memset((void*)(uintptr_t(aPtr) + aSize), kAllocPoison, aOldSize - aSize);
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} else if (opt_zero && aSize > aOldSize) {
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memset((void*)(uintptr_t(aPtr) + aOldSize), 0, aSize - aOldSize);
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}
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return aPtr;
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}
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static inline void*
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@ -3781,45 +3810,26 @@ arena_t::arena_t()
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// Initialize bins.
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prev_run_size = pagesize;
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SizeClass sizeClass(1);
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// (2^n)-spaced tiny bins.
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for (i = 0; i < ntbins; i++) {
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for (i = 0;; i++) {
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bin = &mBins[i];
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bin->mCurrentRun = nullptr;
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bin->mNonFullRuns.Init();
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bin->mSizeClass = (1ULL << (TINY_MIN_2POW + i));
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prev_run_size = arena_bin_run_size_calc(bin, prev_run_size);
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bin->mNumRuns = 0;
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}
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// Quantum-spaced bins.
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for (; i < ntbins + nqbins; i++) {
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bin = &mBins[i];
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bin->mCurrentRun = nullptr;
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bin->mNonFullRuns.Init();
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bin->mSizeClass = quantum * (i - ntbins + 1);
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prev_run_size = arena_bin_run_size_calc(bin, prev_run_size);
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bin->mNumRuns = 0;
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}
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// (2^n)-spaced sub-page bins.
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for (; i < ntbins + nqbins + nsbins; i++) {
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bin = &mBins[i];
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bin->mCurrentRun = nullptr;
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bin->mNonFullRuns.Init();
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bin->mSizeClass = (small_max << (i - (ntbins + nqbins) + 1));
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bin->mSizeClass = sizeClass.Size();
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prev_run_size = arena_bin_run_size_calc(bin, prev_run_size);
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bin->mNumRuns = 0;
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// SizeClass doesn't want sizes larger than bin_maxclass for now.
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if (sizeClass.Size() == bin_maxclass) {
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break;
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}
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sizeClass = sizeClass.Next();
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}
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MOZ_ASSERT(i == ntbins + nqbins + nsbins - 1);
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#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
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mMagic = ARENA_MAGIC;
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@ -4476,24 +4486,9 @@ template<>
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inline size_t
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MozJemalloc::malloc_good_size(size_t aSize)
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{
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// This duplicates the logic in imalloc(), arena_malloc() and
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// arena_t::MallocSmall().
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if (aSize < small_min) {
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// Small (tiny).
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aSize = RoundUpPow2(aSize);
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// We omit the #ifdefs from arena_t::MallocSmall() --
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// it can be inaccurate with its size in some cases, but this
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// function must be accurate.
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if (aSize < (1U << TINY_MIN_2POW)) {
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aSize = (1U << TINY_MIN_2POW);
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}
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} else if (aSize <= small_max) {
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// Small (quantum-spaced).
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aSize = QUANTUM_CEILING(aSize);
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} else if (aSize <= bin_maxclass) {
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// Small (sub-page).
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aSize = RoundUpPow2(aSize);
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if (aSize <= bin_maxclass) {
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// Small
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aSize = SizeClass(aSize).Size();
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} else if (aSize <= arena_maxclass) {
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// Large.
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aSize = PAGE_CEILING(aSize);
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