X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=folly%2FIndexedMemPool.h;h=d9e84935a077cedec6acc8fd75fe729d0507fed1;hb=49399f7cf36dfdda58e1bc01f2c9a1bc7a4ed400;hp=bf35b559162e074b7b7ff7ba4e4e7daeb02712c5;hpb=35fcff936a0ba58986269fb05689843f99e89eb5;p=folly.git diff --git a/folly/IndexedMemPool.h b/folly/IndexedMemPool.h index bf35b559..d9e84935 100644 --- a/folly/IndexedMemPool.h +++ b/folly/IndexedMemPool.h @@ -1,5 +1,5 @@ /* - * Copyright 2016 Facebook, Inc. + * Copyright 2017 Facebook, Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. @@ -17,8 +17,9 @@ #pragma once #include -#include #include +#include +#include #include #include #include @@ -83,12 +84,13 @@ struct IndexedMemPoolRecycler; /// constructed, but delays element construction. This means that only /// elements that are actually returned to the caller get paged into the /// process's resident set (RSS). -template class Atom = std::atomic, - bool EagerRecycleWhenTrivial = false, - bool EagerRecycleWhenNotTrivial = true> +template < + typename T, + uint32_t NumLocalLists_ = 32, + uint32_t LocalListLimit_ = 200, + template class Atom = std::atomic, + bool EagerRecycleWhenTrivial = false, + bool EagerRecycleWhenNotTrivial = true> struct IndexedMemPool : boost::noncopyable { typedef T value_type; @@ -111,9 +113,11 @@ struct IndexedMemPool : boost::noncopyable { // of bits required to hold indices from a pool, given its capacity static constexpr uint32_t maxIndexForCapacity(uint32_t capacity) { - // index of uint32_t(-1) == UINT32_MAX is reserved for isAllocated tracking - return std::min(uint64_t(capacity) + (NumLocalLists - 1) * LocalListLimit, - uint64_t(uint32_t(-1) - 1)); + // index of std::numeric_limits::max() is reserved for isAllocated + // tracking + return uint32_t(std::min( + uint64_t(capacity) + (NumLocalLists - 1) * LocalListLimit, + uint64_t(std::numeric_limits::max() - 1))); } static constexpr uint32_t capacityForMaxIndex(uint32_t maxIndex) { @@ -129,7 +133,7 @@ struct IndexedMemPool : boost::noncopyable { , globalHead_(TaggedPtr{}) { const size_t needed = sizeof(Slot) * (actualCapacity_ + 1); - size_t pagesize = sysconf(_SC_PAGESIZE); + size_t pagesize = size_t(sysconf(_SC_PAGESIZE)); mmapLength_ = ((needed - 1) & ~(pagesize - 1)) + pagesize; assert(needed <= mmapLength_ && mmapLength_ < needed + pagesize); assert((mmapLength_ % pagesize) == 0); @@ -146,7 +150,11 @@ struct IndexedMemPool : boost::noncopyable { /// Destroys all of the contained elements ~IndexedMemPool() { if (!eagerRecycle()) { - for (size_t i = size_; i > 0; --i) { + // Take the minimum since it is possible that size_ > actualCapacity_. + // This can happen if there are multiple concurrent requests + // when size_ == actualCapacity_ - 1. + uint32_t last = std::min(uint32_t(size_), uint32_t(actualCapacity_)); + for (uint32_t i = last; i > 0; --i) { slots_[i].~Slot(); } } @@ -157,7 +165,7 @@ struct IndexedMemPool : boost::noncopyable { /// simultaneously allocated and not yet recycled. Because of the /// local lists it is possible that more elements than this are returned /// successfully - size_t capacity() { + uint32_t capacity() { return capacityForMaxIndex(actualCapacity_); } @@ -217,7 +225,7 @@ struct IndexedMemPool : boost::noncopyable { auto slot = reinterpret_cast( reinterpret_cast(elem) - offsetof(Slot, elem)); - auto rv = slot - slots_; + auto rv = uint32_t(slot - slots_); // this assert also tests that rv is in range assert(elem == &(*this)[rv]); @@ -226,7 +234,7 @@ struct IndexedMemPool : boost::noncopyable { /// Returns true iff idx has been alloc()ed and not recycleIndex()ed bool isAllocated(uint32_t idx) const { - return slot(idx).localNext == uint32_t(-1); + return slot(idx).localNext.load(std::memory_order_relaxed) == uint32_t(-1); } @@ -235,8 +243,8 @@ struct IndexedMemPool : boost::noncopyable { struct Slot { T elem; - uint32_t localNext; - uint32_t globalNext; + Atom localNext; + Atom globalNext; Slot() : localNext{}, globalNext{} {} }; @@ -291,15 +299,15 @@ struct IndexedMemPool : boost::noncopyable { ////////// fields + /// the number of bytes allocated from mmap, which is a multiple of + /// the page size of the machine + size_t mmapLength_; + /// the actual number of slots that we will allocate, to guarantee /// that we will satisfy the capacity requested at construction time. /// They will be numbered 1..actualCapacity_ (note the 1-based counting), /// and occupy slots_[1..actualCapacity_]. - size_t actualCapacity_; - - /// the number of bytes allocated from mmap, which is a multiple of - /// the page size of the machine - size_t mmapLength_; + uint32_t actualCapacity_; /// this records the number of slots that have actually been constructed. /// To allow use of atomic ++ instead of CAS, we let this overflow. @@ -322,7 +330,7 @@ struct IndexedMemPool : boost::noncopyable { ///////////// private methods - size_t slotIndex(uint32_t idx) const { + uint32_t slotIndex(uint32_t idx) const { assert(0 < idx && idx <= actualCapacity_ && idx <= size_.load(std::memory_order_acquire)); @@ -342,7 +350,7 @@ struct IndexedMemPool : boost::noncopyable { void globalPush(Slot& s, uint32_t localHead) { while (true) { TaggedPtr gh = globalHead_.load(std::memory_order_acquire); - s.globalNext = gh.idx; + s.globalNext.store(gh.idx, std::memory_order_relaxed); if (globalHead_.compare_exchange_strong(gh, gh.withIdx(localHead))) { // success return; @@ -355,7 +363,7 @@ struct IndexedMemPool : boost::noncopyable { Slot& s = slot(idx); TaggedPtr h = head.load(std::memory_order_acquire); while (true) { - s.localNext = h.idx; + s.localNext.store(h.idx, std::memory_order_relaxed); if (h.size() == LocalListLimit) { // push will overflow local list, steal it instead @@ -379,8 +387,11 @@ struct IndexedMemPool : boost::noncopyable { uint32_t globalPop() { while (true) { TaggedPtr gh = globalHead_.load(std::memory_order_acquire); - if (gh.idx == 0 || globalHead_.compare_exchange_strong( - gh, gh.withIdx(slot(gh.idx).globalNext))) { + if (gh.idx == 0 || + globalHead_.compare_exchange_strong( + gh, + gh.withIdx( + slot(gh.idx).globalNext.load(std::memory_order_relaxed)))) { // global list is empty, or pop was successful return gh.idx; } @@ -394,10 +405,10 @@ struct IndexedMemPool : boost::noncopyable { if (h.idx != 0) { // local list is non-empty, try to pop Slot& s = slot(h.idx); - if (head.compare_exchange_strong( - h, h.withIdx(s.localNext).withSizeDecr())) { + auto next = s.localNext.load(std::memory_order_relaxed); + if (head.compare_exchange_strong(h, h.withIdx(next).withSizeDecr())) { // success - s.localNext = uint32_t(-1); + s.localNext.store(uint32_t(-1), std::memory_order_relaxed); return h.idx; } continue; @@ -417,15 +428,16 @@ struct IndexedMemPool : boost::noncopyable { T* ptr = &slot(idx).elem; new (ptr) T(); } - slot(idx).localNext = uint32_t(-1); + slot(idx).localNext.store(uint32_t(-1), std::memory_order_relaxed); return idx; } Slot& s = slot(idx); + auto next = s.localNext.load(std::memory_order_relaxed); if (head.compare_exchange_strong( - h, h.withIdx(s.localNext).withSize(LocalListLimit))) { + h, h.withIdx(next).withSize(LocalListLimit))) { // global list moved to local list, keep head for us - s.localNext = uint32_t(-1); + s.localNext.store(uint32_t(-1), std::memory_order_relaxed); return idx; } // local bulk push failed, return idx to the global list and try again