mem_plan9.go

Documentation: runtime

     1  // Copyright 2010 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  package runtime
     6  
     7  import "unsafe"
     8  
     9  const memDebug = false
    10  
    11  var bloc uintptr
    12  var blocMax uintptr
    13  var memlock mutex
    14  
    15  type memHdr struct {
    16  	next memHdrPtr
    17  	size uintptr
    18  }
    19  
    20  var memFreelist memHdrPtr // sorted in ascending order
    21  
    22  type memHdrPtr uintptr
    23  
    24  func (p memHdrPtr) ptr() *memHdr   { return (*memHdr)(unsafe.Pointer(p)) }
    25  func (p *memHdrPtr) set(x *memHdr) { *p = memHdrPtr(unsafe.Pointer(x)) }
    26  
    27  func memAlloc(n uintptr) unsafe.Pointer {
    28  	n = memRound(n)
    29  	var prevp *memHdr
    30  	for p := memFreelist.ptr(); p != nil; p = p.next.ptr() {
    31  		if p.size >= n {
    32  			if p.size == n {
    33  				if prevp != nil {
    34  					prevp.next = p.next
    35  				} else {
    36  					memFreelist = p.next
    37  				}
    38  			} else {
    39  				p.size -= n
    40  				p = (*memHdr)(add(unsafe.Pointer(p), p.size))
    41  			}
    42  			*p = memHdr{}
    43  			return unsafe.Pointer(p)
    44  		}
    45  		prevp = p
    46  	}
    47  	return sbrk(n)
    48  }
    49  
    50  func memFree(ap unsafe.Pointer, n uintptr) {
    51  	n = memRound(n)
    52  	memclrNoHeapPointers(ap, n)
    53  	bp := (*memHdr)(ap)
    54  	bp.size = n
    55  	bpn := uintptr(ap)
    56  	if memFreelist == 0 {
    57  		bp.next = 0
    58  		memFreelist.set(bp)
    59  		return
    60  	}
    61  	p := memFreelist.ptr()
    62  	if bpn < uintptr(unsafe.Pointer(p)) {
    63  		memFreelist.set(bp)
    64  		if bpn+bp.size == uintptr(unsafe.Pointer(p)) {
    65  			bp.size += p.size
    66  			bp.next = p.next
    67  			*p = memHdr{}
    68  		} else {
    69  			bp.next.set(p)
    70  		}
    71  		return
    72  	}
    73  	for ; p.next != 0; p = p.next.ptr() {
    74  		if bpn > uintptr(unsafe.Pointer(p)) && bpn < uintptr(unsafe.Pointer(p.next)) {
    75  			break
    76  		}
    77  	}
    78  	if bpn+bp.size == uintptr(unsafe.Pointer(p.next)) {
    79  		bp.size += p.next.ptr().size
    80  		bp.next = p.next.ptr().next
    81  		*p.next.ptr() = memHdr{}
    82  	} else {
    83  		bp.next = p.next
    84  	}
    85  	if uintptr(unsafe.Pointer(p))+p.size == bpn {
    86  		p.size += bp.size
    87  		p.next = bp.next
    88  		*bp = memHdr{}
    89  	} else {
    90  		p.next.set(bp)
    91  	}
    92  }
    93  
    94  func memCheck() {
    95  	if memDebug == false {
    96  		return
    97  	}
    98  	for p := memFreelist.ptr(); p != nil && p.next != 0; p = p.next.ptr() {
    99  		if uintptr(unsafe.Pointer(p)) == uintptr(unsafe.Pointer(p.next)) {
   100  			print("runtime: ", unsafe.Pointer(p), " == ", unsafe.Pointer(p.next), "\n")
   101  			throw("mem: infinite loop")
   102  		}
   103  		if uintptr(unsafe.Pointer(p)) > uintptr(unsafe.Pointer(p.next)) {
   104  			print("runtime: ", unsafe.Pointer(p), " > ", unsafe.Pointer(p.next), "\n")
   105  			throw("mem: unordered list")
   106  		}
   107  		if uintptr(unsafe.Pointer(p))+p.size > uintptr(unsafe.Pointer(p.next)) {
   108  			print("runtime: ", unsafe.Pointer(p), "+", p.size, " > ", unsafe.Pointer(p.next), "\n")
   109  			throw("mem: overlapping blocks")
   110  		}
   111  		for b := add(unsafe.Pointer(p), unsafe.Sizeof(memHdr{})); uintptr(b) < uintptr(unsafe.Pointer(p))+p.size; b = add(b, 1) {
   112  			if *(*byte)(b) != 0 {
   113  				print("runtime: value at addr ", b, " with offset ", uintptr(b)-uintptr(unsafe.Pointer(p)), " in block ", p, " of size ", p.size, " is not zero\n")
   114  				throw("mem: uninitialised memory")
   115  			}
   116  		}
   117  	}
   118  }
   119  
   120  func memRound(p uintptr) uintptr {
   121  	return (p + _PAGESIZE - 1) &^ (_PAGESIZE - 1)
   122  }
   123  
   124  func initBloc() {
   125  	bloc = memRound(firstmoduledata.end)
   126  	blocMax = bloc
   127  }
   128  
   129  func sbrk(n uintptr) unsafe.Pointer {
   130  	// Plan 9 sbrk from /sys/src/libc/9sys/sbrk.c
   131  	bl := bloc
   132  	n = memRound(n)
   133  	if bl+n > blocMax {
   134  		if brk_(unsafe.Pointer(bl+n)) < 0 {
   135  			return nil
   136  		}
   137  		blocMax = bl + n
   138  	}
   139  	bloc += n
   140  	return unsafe.Pointer(bl)
   141  }
   142  
   143  func sysAlloc(n uintptr, sysStat *sysMemStat) unsafe.Pointer {
   144  	lock(&memlock)
   145  	p := memAlloc(n)
   146  	memCheck()
   147  	unlock(&memlock)
   148  	if p != nil {
   149  		sysStat.add(int64(n))
   150  	}
   151  	return p
   152  }
   153  
   154  func sysFree(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
   155  	sysStat.add(-int64(n))
   156  	lock(&memlock)
   157  	if uintptr(v)+n == bloc {
   158  		// Address range being freed is at the end of memory,
   159  		// so record a new lower value for end of memory.
   160  		// Can't actually shrink address space because segment is shared.
   161  		memclrNoHeapPointers(v, n)
   162  		bloc -= n
   163  	} else {
   164  		memFree(v, n)
   165  		memCheck()
   166  	}
   167  	unlock(&memlock)
   168  }
   169  
   170  func sysUnused(v unsafe.Pointer, n uintptr) {
   171  }
   172  
   173  func sysUsed(v unsafe.Pointer, n uintptr) {
   174  }
   175  
   176  func sysHugePage(v unsafe.Pointer, n uintptr) {
   177  }
   178  
   179  func sysMap(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
   180  	// sysReserve has already allocated all heap memory,
   181  	// but has not adjusted stats.
   182  	sysStat.add(int64(n))
   183  }
   184  
   185  func sysFault(v unsafe.Pointer, n uintptr) {
   186  }
   187  
   188  func sysReserve(v unsafe.Pointer, n uintptr) unsafe.Pointer {
   189  	lock(&memlock)
   190  	var p unsafe.Pointer
   191  	if uintptr(v) == bloc {
   192  		// Address hint is the current end of memory,
   193  		// so try to extend the address space.
   194  		p = sbrk(n)
   195  	}
   196  	if p == nil && v == nil {
   197  		p = memAlloc(n)
   198  		memCheck()
   199  	}
   200  	unlock(&memlock)
   201  	return p
   202  }
   203
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