425 lines
15 KiB
C++
425 lines
15 KiB
C++
//===-- release.h -----------------------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef SCUDO_RELEASE_H_
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#define SCUDO_RELEASE_H_
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#include "common.h"
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#include "list.h"
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#include "mutex.h"
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namespace scudo {
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class ReleaseRecorder {
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public:
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ReleaseRecorder(uptr Base, MapPlatformData *Data = nullptr)
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: Base(Base), Data(Data) {}
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uptr getReleasedRangesCount() const { return ReleasedRangesCount; }
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uptr getReleasedBytes() const { return ReleasedBytes; }
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uptr getBase() const { return Base; }
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// Releases [From, To) range of pages back to OS.
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void releasePageRangeToOS(uptr From, uptr To) {
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const uptr Size = To - From;
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releasePagesToOS(Base, From, Size, Data);
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ReleasedRangesCount++;
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ReleasedBytes += Size;
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}
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private:
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uptr ReleasedRangesCount = 0;
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uptr ReleasedBytes = 0;
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uptr Base = 0;
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MapPlatformData *Data = nullptr;
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};
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// A Region page map is used to record the usage of pages in the regions. It
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// implements a packed array of Counters. Each counter occupies 2^N bits, enough
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// to store counter's MaxValue. Ctor will try to use a static buffer first, and
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// if that fails (the buffer is too small or already locked), will allocate the
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// required Buffer via map(). The caller is expected to check whether the
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// initialization was successful by checking isAllocated() result. For
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// performance sake, none of the accessors check the validity of the arguments,
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// It is assumed that Index is always in [0, N) range and the value is not
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// incremented past MaxValue.
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class RegionPageMap {
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public:
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RegionPageMap()
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: Regions(0),
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NumCounters(0),
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CounterSizeBitsLog(0),
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CounterMask(0),
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PackingRatioLog(0),
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BitOffsetMask(0),
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SizePerRegion(0),
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BufferSize(0),
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Buffer(nullptr) {}
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RegionPageMap(uptr NumberOfRegions, uptr CountersPerRegion, uptr MaxValue) {
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reset(NumberOfRegions, CountersPerRegion, MaxValue);
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}
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~RegionPageMap() {
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if (!isAllocated())
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return;
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if (Buffer == &StaticBuffer[0])
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Mutex.unlock();
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else
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unmap(reinterpret_cast<void *>(Buffer),
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roundUpTo(BufferSize, getPageSizeCached()));
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Buffer = nullptr;
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}
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void reset(uptr NumberOfRegion, uptr CountersPerRegion, uptr MaxValue) {
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DCHECK_GT(NumberOfRegion, 0);
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DCHECK_GT(CountersPerRegion, 0);
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DCHECK_GT(MaxValue, 0);
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Regions = NumberOfRegion;
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NumCounters = CountersPerRegion;
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constexpr uptr MaxCounterBits = sizeof(*Buffer) * 8UL;
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// Rounding counter storage size up to the power of two allows for using
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// bit shifts calculating particular counter's Index and offset.
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const uptr CounterSizeBits =
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roundUpToPowerOfTwo(getMostSignificantSetBitIndex(MaxValue) + 1);
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DCHECK_LE(CounterSizeBits, MaxCounterBits);
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CounterSizeBitsLog = getLog2(CounterSizeBits);
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CounterMask = ~(static_cast<uptr>(0)) >> (MaxCounterBits - CounterSizeBits);
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const uptr PackingRatio = MaxCounterBits >> CounterSizeBitsLog;
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DCHECK_GT(PackingRatio, 0);
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PackingRatioLog = getLog2(PackingRatio);
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BitOffsetMask = PackingRatio - 1;
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SizePerRegion =
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roundUpTo(NumCounters, static_cast<uptr>(1U) << PackingRatioLog) >>
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PackingRatioLog;
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BufferSize = SizePerRegion * sizeof(*Buffer) * Regions;
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if (BufferSize <= (StaticBufferCount * sizeof(Buffer[0])) &&
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Mutex.tryLock()) {
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Buffer = &StaticBuffer[0];
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memset(Buffer, 0, BufferSize);
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} else {
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Buffer = reinterpret_cast<uptr *>(
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map(nullptr, roundUpTo(BufferSize, getPageSizeCached()),
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"scudo:counters", MAP_ALLOWNOMEM, &MapData));
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}
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}
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bool isAllocated() const { return !!Buffer; }
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uptr getCount() const { return NumCounters; }
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uptr get(uptr Region, uptr I) const {
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DCHECK_LT(Region, Regions);
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DCHECK_LT(I, NumCounters);
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const uptr Index = I >> PackingRatioLog;
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const uptr BitOffset = (I & BitOffsetMask) << CounterSizeBitsLog;
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return (Buffer[Region * SizePerRegion + Index] >> BitOffset) & CounterMask;
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}
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void inc(uptr Region, uptr I) const {
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DCHECK_LT(get(Region, I), CounterMask);
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const uptr Index = I >> PackingRatioLog;
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const uptr BitOffset = (I & BitOffsetMask) << CounterSizeBitsLog;
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DCHECK_LT(BitOffset, SCUDO_WORDSIZE);
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DCHECK_EQ(isAllCounted(Region, I), false);
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Buffer[Region * SizePerRegion + Index] += static_cast<uptr>(1U)
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<< BitOffset;
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}
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void incRange(uptr Region, uptr From, uptr To) const {
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DCHECK_LE(From, To);
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const uptr Top = Min(To + 1, NumCounters);
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for (uptr I = From; I < Top; I++)
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inc(Region, I);
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}
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// Set the counter to the max value. Note that the max number of blocks in a
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// page may vary. To provide an easier way to tell if all the blocks are
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// counted for different pages, set to the same max value to denote the
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// all-counted status.
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void setAsAllCounted(uptr Region, uptr I) const {
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DCHECK_LE(get(Region, I), CounterMask);
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const uptr Index = I >> PackingRatioLog;
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const uptr BitOffset = (I & BitOffsetMask) << CounterSizeBitsLog;
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DCHECK_LT(BitOffset, SCUDO_WORDSIZE);
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Buffer[Region * SizePerRegion + Index] |= CounterMask << BitOffset;
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}
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bool isAllCounted(uptr Region, uptr I) const {
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return get(Region, I) == CounterMask;
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}
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uptr getBufferSize() const { return BufferSize; }
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static const uptr StaticBufferCount = 2048U;
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private:
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uptr Regions;
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uptr NumCounters;
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uptr CounterSizeBitsLog;
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uptr CounterMask;
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uptr PackingRatioLog;
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uptr BitOffsetMask;
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uptr SizePerRegion;
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uptr BufferSize;
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uptr *Buffer;
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[[no_unique_address]] MapPlatformData MapData = {};
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static HybridMutex Mutex;
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static uptr StaticBuffer[StaticBufferCount];
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};
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template <class ReleaseRecorderT> class FreePagesRangeTracker {
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public:
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explicit FreePagesRangeTracker(ReleaseRecorderT &Recorder)
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: Recorder(Recorder), PageSizeLog(getLog2(getPageSizeCached())) {}
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void processNextPage(bool Released) {
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if (Released) {
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if (!InRange) {
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CurrentRangeStatePage = CurrentPage;
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InRange = true;
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}
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} else {
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closeOpenedRange();
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}
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CurrentPage++;
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}
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void skipPages(uptr N) {
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closeOpenedRange();
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CurrentPage += N;
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}
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void finish() { closeOpenedRange(); }
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private:
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void closeOpenedRange() {
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if (InRange) {
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Recorder.releasePageRangeToOS((CurrentRangeStatePage << PageSizeLog),
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(CurrentPage << PageSizeLog));
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InRange = false;
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}
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}
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ReleaseRecorderT &Recorder;
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const uptr PageSizeLog;
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bool InRange = false;
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uptr CurrentPage = 0;
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uptr CurrentRangeStatePage = 0;
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};
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struct PageReleaseContext {
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PageReleaseContext(uptr BlockSize, uptr RegionSize, uptr NumberOfRegions) :
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BlockSize(BlockSize),
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RegionSize(RegionSize),
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NumberOfRegions(NumberOfRegions) {
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PageSize = getPageSizeCached();
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if (BlockSize <= PageSize) {
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if (PageSize % BlockSize == 0) {
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// Same number of chunks per page, no cross overs.
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FullPagesBlockCountMax = PageSize / BlockSize;
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SameBlockCountPerPage = true;
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} else if (BlockSize % (PageSize % BlockSize) == 0) {
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// Some chunks are crossing page boundaries, which means that the page
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// contains one or two partial chunks, but all pages contain the same
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// number of chunks.
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FullPagesBlockCountMax = PageSize / BlockSize + 1;
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SameBlockCountPerPage = true;
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} else {
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// Some chunks are crossing page boundaries, which means that the page
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// contains one or two partial chunks.
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FullPagesBlockCountMax = PageSize / BlockSize + 2;
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SameBlockCountPerPage = false;
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}
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} else {
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if (BlockSize % PageSize == 0) {
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// One chunk covers multiple pages, no cross overs.
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FullPagesBlockCountMax = 1;
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SameBlockCountPerPage = true;
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} else {
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// One chunk covers multiple pages, Some chunks are crossing page
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// boundaries. Some pages contain one chunk, some contain two.
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FullPagesBlockCountMax = 2;
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SameBlockCountPerPage = false;
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}
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}
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PagesCount = roundUpTo(RegionSize, PageSize) / PageSize;
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PageSizeLog = getLog2(PageSize);
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RoundedRegionSize = PagesCount << PageSizeLog;
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RoundedSize = NumberOfRegions * RoundedRegionSize;
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}
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// PageMap is lazily allocated when markFreeBlocks() is invoked.
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bool hasBlockMarked() const {
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return PageMap.isAllocated();
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}
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void ensurePageMapAllocated() {
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if (PageMap.isAllocated())
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return;
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PageMap.reset(NumberOfRegions, PagesCount, FullPagesBlockCountMax);
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DCHECK(PageMap.isAllocated());
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}
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template<class TransferBatchT, typename DecompactPtrT>
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void markFreeBlocks(const IntrusiveList<TransferBatchT> &FreeList,
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DecompactPtrT DecompactPtr, uptr Base) {
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ensurePageMapAllocated();
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// Iterate over free chunks and count how many free chunks affect each
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// allocated page.
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if (BlockSize <= PageSize && PageSize % BlockSize == 0) {
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// Each chunk affects one page only.
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for (const auto &It : FreeList) {
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for (u16 I = 0; I < It.getCount(); I++) {
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const uptr P = DecompactPtr(It.get(I)) - Base;
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if (P >= RoundedSize)
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continue;
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const uptr RegionIndex = NumberOfRegions == 1U ? 0 : P / RegionSize;
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const uptr PInRegion = P - RegionIndex * RegionSize;
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PageMap.inc(RegionIndex, PInRegion >> PageSizeLog);
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}
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}
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} else {
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// In all other cases chunks might affect more than one page.
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DCHECK_GE(RegionSize, BlockSize);
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const uptr LastBlockInRegion =
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((RegionSize / BlockSize) - 1U) * BlockSize;
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for (const auto &It : FreeList) {
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for (u16 I = 0; I < It.getCount(); I++) {
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const uptr P = DecompactPtr(It.get(I)) - Base;
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if (P >= RoundedSize)
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continue;
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const uptr RegionIndex = NumberOfRegions == 1U ? 0 : P / RegionSize;
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uptr PInRegion = P - RegionIndex * RegionSize;
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PageMap.incRange(RegionIndex, PInRegion >> PageSizeLog,
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(PInRegion + BlockSize - 1) >> PageSizeLog);
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// The last block in a region might straddle a page, so if it's
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// free, we mark the following "pretend" memory block(s) as free.
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if (PInRegion == LastBlockInRegion) {
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PInRegion += BlockSize;
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while (PInRegion < RoundedRegionSize) {
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PageMap.incRange(RegionIndex, PInRegion >> PageSizeLog,
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(PInRegion + BlockSize - 1) >> PageSizeLog);
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PInRegion += BlockSize;
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}
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}
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}
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}
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}
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}
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uptr BlockSize;
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uptr RegionSize;
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uptr NumberOfRegions;
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uptr PageSize;
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uptr PagesCount;
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uptr PageSizeLog;
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uptr RoundedRegionSize;
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uptr RoundedSize;
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uptr FullPagesBlockCountMax;
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bool SameBlockCountPerPage;
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RegionPageMap PageMap;
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};
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// Try to release the page which doesn't have any in-used block, i.e., they are
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// all free blocks. The `PageMap` will record the number of free blocks in each
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// page.
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template <class ReleaseRecorderT, typename SkipRegionT>
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NOINLINE void
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releaseFreeMemoryToOS(PageReleaseContext &Context,
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ReleaseRecorderT &Recorder, SkipRegionT SkipRegion) {
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const uptr PageSize = Context.PageSize;
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const uptr BlockSize = Context.BlockSize;
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const uptr PagesCount = Context.PagesCount;
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const uptr NumberOfRegions = Context.NumberOfRegions;
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const uptr FullPagesBlockCountMax = Context.FullPagesBlockCountMax;
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const bool SameBlockCountPerPage = Context.SameBlockCountPerPage;
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RegionPageMap &PageMap = Context.PageMap;
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// Iterate over pages detecting ranges of pages with chunk Counters equal
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// to the expected number of chunks for the particular page.
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FreePagesRangeTracker<ReleaseRecorderT> RangeTracker(Recorder);
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if (SameBlockCountPerPage) {
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// Fast path, every page has the same number of chunks affecting it.
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for (uptr I = 0; I < NumberOfRegions; I++) {
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if (SkipRegion(I)) {
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RangeTracker.skipPages(PagesCount);
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continue;
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}
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for (uptr J = 0; J < PagesCount; J++) {
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const bool CanRelease = PageMap.get(I, J) == FullPagesBlockCountMax;
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if (CanRelease)
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PageMap.setAsAllCounted(I, J);
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RangeTracker.processNextPage(CanRelease);
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}
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}
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} else {
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// Slow path, go through the pages keeping count how many chunks affect
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// each page.
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const uptr Pn = BlockSize < PageSize ? PageSize / BlockSize : 1;
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const uptr Pnc = Pn * BlockSize;
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// The idea is to increment the current page pointer by the first chunk
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// size, middle portion size (the portion of the page covered by chunks
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// except the first and the last one) and then the last chunk size, adding
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// up the number of chunks on the current page and checking on every step
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// whether the page boundary was crossed.
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for (uptr I = 0; I < NumberOfRegions; I++) {
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if (SkipRegion(I)) {
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RangeTracker.skipPages(PagesCount);
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continue;
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}
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uptr PrevPageBoundary = 0;
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uptr CurrentBoundary = 0;
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for (uptr J = 0; J < PagesCount; J++) {
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const uptr PageBoundary = PrevPageBoundary + PageSize;
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uptr BlocksPerPage = Pn;
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if (CurrentBoundary < PageBoundary) {
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if (CurrentBoundary > PrevPageBoundary)
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BlocksPerPage++;
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CurrentBoundary += Pnc;
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if (CurrentBoundary < PageBoundary) {
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BlocksPerPage++;
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CurrentBoundary += BlockSize;
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}
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}
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PrevPageBoundary = PageBoundary;
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const bool CanRelease = PageMap.get(I, J) == BlocksPerPage;
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if (CanRelease)
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PageMap.setAsAllCounted(I, J);
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RangeTracker.processNextPage(CanRelease);
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}
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}
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}
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RangeTracker.finish();
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}
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// An overload releaseFreeMemoryToOS which doesn't require the page usage
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// information after releasing.
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template <class TransferBatchT, class ReleaseRecorderT, typename DecompactPtrT,
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typename SkipRegionT>
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NOINLINE void
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releaseFreeMemoryToOS(const IntrusiveList<TransferBatchT> &FreeList,
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uptr RegionSize, uptr NumberOfRegions, uptr BlockSize,
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ReleaseRecorderT &Recorder, DecompactPtrT DecompactPtr,
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SkipRegionT SkipRegion) {
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PageReleaseContext Context(BlockSize, RegionSize, NumberOfRegions);
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Context.markFreeBlocks(FreeList, DecompactPtr, Recorder.getBase());
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releaseFreeMemoryToOS(Context, Recorder, SkipRegion);
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}
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} // namespace scudo
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#endif // SCUDO_RELEASE_H_
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