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// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build 386 || arm || mips || mipsle || wasm
// wasm is a treated as a 32-bit architecture for the purposes of the page
// allocator, even though it has 64-bit pointers. This is because any wasm
// pointer always has its top 32 bits as zero, so the effective heap address
// space is only 2^32 bytes in size (see heapAddrBits).
package runtime
import (
"runtime/internal/atomic"
"unsafe"
)
const (
// The number of levels in the radix tree.
summaryLevels = 4
// Constants for testing.
pageAlloc32Bit = 1
pageAlloc64Bit = 0
// Number of bits needed to represent all indices into the L1 of the
// chunks map.
//
// See (*pageAlloc).chunks for more details. Update the documentation
// there should this number change.
pallocChunksL1Bits = 0
)
// See comment in mpagealloc_64bit.go.
var levelBits = [summaryLevels]uint{
summaryL0Bits,
summaryLevelBits,
summaryLevelBits,
summaryLevelBits,
}
// See comment in mpagealloc_64bit.go.
var levelShift = [summaryLevels]uint{
heapAddrBits - summaryL0Bits,
heapAddrBits - summaryL0Bits - 1*summaryLevelBits,
heapAddrBits - summaryL0Bits - 2*summaryLevelBits,
heapAddrBits - summaryL0Bits - 3*summaryLevelBits,
}
// See comment in mpagealloc_64bit.go.
var levelLogPages = [summaryLevels]uint{
logPallocChunkPages + 3*summaryLevelBits,
logPallocChunkPages + 2*summaryLevelBits,
logPallocChunkPages + 1*summaryLevelBits,
logPallocChunkPages,
}
// scavengeIndexArray is the backing store for p.scav.index.chunks.
// On 32-bit platforms, it's small enough to just be a global.
var scavengeIndexArray [((1 << heapAddrBits) / pallocChunkBytes) / 8]atomic.Uint8
// See mpagealloc_64bit.go for details.
func (p *pageAlloc) sysInit() {
// Calculate how much memory all our entries will take up.
//
// This should be around 12 KiB or less.
totalSize := uintptr(0)
for l := 0; l < summaryLevels; l++ {
totalSize += (uintptr(1) << (heapAddrBits - levelShift[l])) * pallocSumBytes
}
totalSize = alignUp(totalSize, physPageSize)
// Reserve memory for all levels in one go. There shouldn't be much for 32-bit.
reservation := sysReserve(nil, totalSize)
if reservation == nil {
throw("failed to reserve page summary memory")
}
// There isn't much. Just map it and mark it as used immediately.
sysMap(reservation, totalSize, p.sysStat)
sysUsed(reservation, totalSize, totalSize)
p.summaryMappedReady += totalSize
// Iterate over the reservation and cut it up into slices.
//
// Maintain i as the byte offset from reservation where
// the new slice should start.
for l, shift := range levelShift {
entries := 1 << (heapAddrBits - shift)
// Put this reservation into a slice.
sl := notInHeapSlice{(*notInHeap)(reservation), 0, entries}
p.summary[l] = *(*[]pallocSum)(unsafe.Pointer(&sl))
reservation = add(reservation, uintptr(entries)*pallocSumBytes)
}
// Set up the scavenge index.
p.scav.index.chunks = scavengeIndexArray[:]
}
// See mpagealloc_64bit.go for details.
func (p *pageAlloc) sysGrow(base, limit uintptr) {
if base%pallocChunkBytes != 0 || limit%pallocChunkBytes != 0 {
print("runtime: base = ", hex(base), ", limit = ", hex(limit), "\n")
throw("sysGrow bounds not aligned to pallocChunkBytes")
}
// Walk up the tree and update the summary slices.
for l := len(p.summary) - 1; l >= 0; l-- {
// Figure out what part of the summary array this new address space needs.
// Note that we need to align the ranges to the block width (1<<levelBits[l])
// at this level because the full block is needed to compute the summary for
// the next level.
lo, hi := addrsToSummaryRange(l, base, limit)
_, hi = blockAlignSummaryRange(l, lo, hi)
if hi > len(p.summary[l]) {
p.summary[l] = p.summary[l][:hi]
}
}
}
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