mpagealloc_64bit.go

     1  // Copyright 2019 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build amd64 || arm64 || mips64 || mips64le || ppc64 || ppc64le || riscv64 || s390x
     6  
     7  package runtime
     8  
     9  import "unsafe"
    10  
    11  const (
    12  	// The number of levels in the radix tree.
    13  	summaryLevels = 5
    14  
    15  	// Constants for testing.
    16  	pageAlloc32Bit = 0
    17  	pageAlloc64Bit = 1
    18  
    19  	// Number of bits needed to represent all indices into the L1 of the
    20  	// chunks map.
    21  	//
    22  	// See (*pageAlloc).chunks for more details. Update the documentation
    23  	// there should this number change.
    24  	pallocChunksL1Bits = 13
    25  )
    26  
    27  // levelBits is the number of bits in the radix for a given level in the super summary
    28  // structure.
    29  //
    30  // The sum of all the entries of levelBits should equal heapAddrBits.
    31  var levelBits = [summaryLevels]uint{
    32  	summaryL0Bits,
    33  	summaryLevelBits,
    34  	summaryLevelBits,
    35  	summaryLevelBits,
    36  	summaryLevelBits,
    37  }
    38  
    39  // levelShift is the number of bits to shift to acquire the radix for a given level
    40  // in the super summary structure.
    41  //
    42  // With levelShift, one can compute the index of the summary at level l related to a
    43  // pointer p by doing:
    44  //   p >> levelShift[l]
    45  var levelShift = [summaryLevels]uint{
    46  	heapAddrBits - summaryL0Bits,
    47  	heapAddrBits - summaryL0Bits - 1*summaryLevelBits,
    48  	heapAddrBits - summaryL0Bits - 2*summaryLevelBits,
    49  	heapAddrBits - summaryL0Bits - 3*summaryLevelBits,
    50  	heapAddrBits - summaryL0Bits - 4*summaryLevelBits,
    51  }
    52  
    53  // levelLogPages is log2 the maximum number of runtime pages in the address space
    54  // a summary in the given level represents.
    55  //
    56  // The leaf level always represents exactly log2 of 1 chunk's worth of pages.
    57  var levelLogPages = [summaryLevels]uint{
    58  	logPallocChunkPages + 4*summaryLevelBits,
    59  	logPallocChunkPages + 3*summaryLevelBits,
    60  	logPallocChunkPages + 2*summaryLevelBits,
    61  	logPallocChunkPages + 1*summaryLevelBits,
    62  	logPallocChunkPages,
    63  }
    64  
    65  // sysInit performs architecture-dependent initialization of fields
    66  // in pageAlloc. pageAlloc should be uninitialized except for sysStat
    67  // if any runtime statistic should be updated.
    68  func (p *pageAlloc) sysInit() {
    69  	// Reserve memory for each level. This will get mapped in
    70  	// as R/W by setArenas.
    71  	for l, shift := range levelShift {
    72  		entries := 1 << (heapAddrBits - shift)
    73  
    74  		// Reserve b bytes of memory anywhere in the address space.
    75  		b := alignUp(uintptr(entries)*pallocSumBytes, physPageSize)
    76  		r := sysReserve(nil, b)
    77  		if r == nil {
    78  			throw("failed to reserve page summary memory")
    79  		}
    80  
    81  		// Put this reservation into a slice.
    82  		sl := notInHeapSlice{(*notInHeap)(r), 0, entries}
    83  		p.summary[l] = *(*[]pallocSum)(unsafe.Pointer(&sl))
    84  	}
    85  }
    86  
    87  // sysGrow performs architecture-dependent operations on heap
    88  // growth for the page allocator, such as mapping in new memory
    89  // for summaries. It also updates the length of the slices in
    90  // [.summary.
    91  //
    92  // base is the base of the newly-added heap memory and limit is
    93  // the first address past the end of the newly-added heap memory.
    94  // Both must be aligned to pallocChunkBytes.
    95  //
    96  // The caller must update p.start and p.end after calling sysGrow.
    97  func (p *pageAlloc) sysGrow(base, limit uintptr) {
    98  	if base%pallocChunkBytes != 0 || limit%pallocChunkBytes != 0 {
    99  		print("runtime: base = ", hex(base), ", limit = ", hex(limit), "\n")
   100  		throw("sysGrow bounds not aligned to pallocChunkBytes")
   101  	}
   102  
   103  	// addrRangeToSummaryRange converts a range of addresses into a range
   104  	// of summary indices which must be mapped to support those addresses
   105  	// in the summary range.
   106  	addrRangeToSummaryRange := func(level int, r addrRange) (int, int) {
   107  		sumIdxBase, sumIdxLimit := addrsToSummaryRange(level, r.base.addr(), r.limit.addr())
   108  		return blockAlignSummaryRange(level, sumIdxBase, sumIdxLimit)
   109  	}
   110  
   111  	// summaryRangeToSumAddrRange converts a range of indices in any
   112  	// level of p.summary into page-aligned addresses which cover that
   113  	// range of indices.
   114  	summaryRangeToSumAddrRange := func(level, sumIdxBase, sumIdxLimit int) addrRange {
   115  		baseOffset := alignDown(uintptr(sumIdxBase)*pallocSumBytes, physPageSize)
   116  		limitOffset := alignUp(uintptr(sumIdxLimit)*pallocSumBytes, physPageSize)
   117  		base := unsafe.Pointer(&p.summary[level][0])
   118  		return addrRange{
   119  			offAddr{uintptr(add(base, baseOffset))},
   120  			offAddr{uintptr(add(base, limitOffset))},
   121  		}
   122  	}
   123  
   124  	// addrRangeToSumAddrRange is a convienience function that converts
   125  	// an address range r to the address range of the given summary level
   126  	// that stores the summaries for r.
   127  	addrRangeToSumAddrRange := func(level int, r addrRange) addrRange {
   128  		sumIdxBase, sumIdxLimit := addrRangeToSummaryRange(level, r)
   129  		return summaryRangeToSumAddrRange(level, sumIdxBase, sumIdxLimit)
   130  	}
   131  
   132  	// Find the first inUse index which is strictly greater than base.
   133  	//
   134  	// Because this function will never be asked remap the same memory
   135  	// twice, this index is effectively the index at which we would insert
   136  	// this new growth, and base will never overlap/be contained within
   137  	// any existing range.
   138  	//
   139  	// This will be used to look at what memory in the summary array is already
   140  	// mapped before and after this new range.
   141  	inUseIndex := p.inUse.findSucc(base)
   142  
   143  	// Walk up the radix tree and map summaries in as needed.
   144  	for l := range p.summary {
   145  		// Figure out what part of the summary array this new address space needs.
   146  		needIdxBase, needIdxLimit := addrRangeToSummaryRange(l, makeAddrRange(base, limit))
   147  
   148  		// Update the summary slices with a new upper-bound. This ensures
   149  		// we get tight bounds checks on at least the top bound.
   150  		//
   151  		// We must do this regardless of whether we map new memory.
   152  		if needIdxLimit > len(p.summary[l]) {
   153  			p.summary[l] = p.summary[l][:needIdxLimit]
   154  		}
   155  
   156  		// Compute the needed address range in the summary array for level l.
   157  		need := summaryRangeToSumAddrRange(l, needIdxBase, needIdxLimit)
   158  
   159  		// Prune need down to what needs to be newly mapped. Some parts of it may
   160  		// already be mapped by what inUse describes due to page alignment requirements
   161  		// for mapping. prune's invariants are guaranteed by the fact that this
   162  		// function will never be asked to remap the same memory twice.
   163  		if inUseIndex > 0 {
   164  			need = need.subtract(addrRangeToSumAddrRange(l, p.inUse.ranges[inUseIndex-1]))
   165  		}
   166  		if inUseIndex < len(p.inUse.ranges) {
   167  			need = need.subtract(addrRangeToSumAddrRange(l, p.inUse.ranges[inUseIndex]))
   168  		}
   169  		// It's possible that after our pruning above, there's nothing new to map.
   170  		if need.size() == 0 {
   171  			continue
   172  		}
   173  
   174  		// Map and commit need.
   175  		sysMap(unsafe.Pointer(need.base.addr()), need.size(), p.sysStat)
   176  		sysUsed(unsafe.Pointer(need.base.addr()), need.size())
   177  	}
   178  }
   179
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