traceallocfree.go

     1  // Copyright 2024 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  // Runtime -> tracer API for memory events.
     6  
     7  package runtime
     8  
     9  import (
    10  	"internal/abi"
    11  	"internal/runtime/sys"
    12  	"internal/trace/tracev2"
    13  )
    14  
    15  // Batch type values for the alloc/free experiment.
    16  const (
    17  	traceAllocFreeTypesBatch = iota // Contains types. [{id, address, size, ptrspan, name length, name string} ...]
    18  	traceAllocFreeInfoBatch         // Contains info for interpreting events. [min heap addr, page size, min heap align, min stack align]
    19  )
    20  
    21  // traceSnapshotMemory takes a snapshot of all runtime memory that there are events for
    22  // (heap spans, heap objects, goroutine stacks, etc.) and writes out events for them.
    23  //
    24  // The world must be stopped and tracing must be enabled when this function is called.
    25  func traceSnapshotMemory(gen uintptr) {
    26  	assertWorldStopped()
    27  
    28  	// Write a batch containing information that'll be necessary to
    29  	// interpret the events.
    30  	var flushed bool
    31  	w := unsafeTraceExpWriter(gen, nil, tracev2.AllocFree)
    32  	w, flushed = w.ensure(1 + 4*traceBytesPerNumber)
    33  	if flushed {
    34  		// Annotate the batch as containing additional info.
    35  		w.byte(byte(traceAllocFreeInfoBatch))
    36  	}
    37  
    38  	// Emit info.
    39  	w.varint(uint64(trace.minPageHeapAddr))
    40  	w.varint(uint64(pageSize))
    41  	w.varint(uint64(minHeapAlign))
    42  	w.varint(uint64(fixedStack))
    43  
    44  	// Finish writing the batch.
    45  	w.flush().end()
    46  
    47  	// Start tracing.
    48  	trace := traceAcquire()
    49  	if !trace.ok() {
    50  		throw("traceSnapshotMemory: tracing is not enabled")
    51  	}
    52  
    53  	// Write out all the heap spans and heap objects.
    54  	for _, s := range mheap_.allspans {
    55  		if s.state.get() == mSpanDead {
    56  			continue
    57  		}
    58  		// It's some kind of span, so trace that it exists.
    59  		trace.SpanExists(s)
    60  
    61  		// Write out allocated objects if it's a heap span.
    62  		if s.state.get() != mSpanInUse {
    63  			continue
    64  		}
    65  
    66  		// Find all allocated objects.
    67  		abits := s.allocBitsForIndex(0)
    68  		for i := uintptr(0); i < uintptr(s.nelems); i++ {
    69  			if abits.index < uintptr(s.freeindex) || abits.isMarked() {
    70  				x := s.base() + i*s.elemsize
    71  				trace.HeapObjectExists(x, s.typePointersOfUnchecked(x).typ)
    72  			}
    73  			abits.advance()
    74  		}
    75  	}
    76  
    77  	// Write out all the goroutine stacks.
    78  	forEachGRace(func(gp *g) {
    79  		trace.GoroutineStackExists(gp.stack.lo, gp.stack.hi-gp.stack.lo)
    80  	})
    81  	traceRelease(trace)
    82  }
    83  
    84  func traceSpanTypeAndClass(s *mspan) traceArg {
    85  	if s.state.get() == mSpanInUse {
    86  		return traceArg(s.spanclass) << 1
    87  	}
    88  	return traceArg(1)
    89  }
    90  
    91  // SpanExists records an event indicating that the span exists.
    92  func (tl traceLocker) SpanExists(s *mspan) {
    93  	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvSpan, traceSpanID(s), traceArg(s.npages), traceSpanTypeAndClass(s))
    94  }
    95  
    96  // SpanAlloc records an event indicating that the span has just been allocated.
    97  func (tl traceLocker) SpanAlloc(s *mspan) {
    98  	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvSpanAlloc, traceSpanID(s), traceArg(s.npages), traceSpanTypeAndClass(s))
    99  }
   100  
   101  // SpanFree records an event indicating that the span is about to be freed.
   102  func (tl traceLocker) SpanFree(s *mspan) {
   103  	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvSpanFree, traceSpanID(s))
   104  }
   105  
   106  // traceSpanID creates a trace ID for the span s for the trace.
   107  func traceSpanID(s *mspan) traceArg {
   108  	return traceArg(uint64(s.base())-trace.minPageHeapAddr) / pageSize
   109  }
   110  
   111  // HeapObjectExists records that an object already exists at addr with the provided type.
   112  // The type is optional, and the size of the slot occupied the object is inferred from the
   113  // span containing it.
   114  func (tl traceLocker) HeapObjectExists(addr uintptr, typ *abi.Type) {
   115  	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvHeapObject, traceHeapObjectID(addr), tl.rtype(typ))
   116  }
   117  
   118  // HeapObjectAlloc records that an object was newly allocated at addr with the provided type.
   119  // The type is optional, and the size of the slot occupied the object is inferred from the
   120  // span containing it.
   121  func (tl traceLocker) HeapObjectAlloc(addr uintptr, typ *abi.Type) {
   122  	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvHeapObjectAlloc, traceHeapObjectID(addr), tl.rtype(typ))
   123  }
   124  
   125  // HeapObjectFree records that an object at addr is about to be freed.
   126  func (tl traceLocker) HeapObjectFree(addr uintptr) {
   127  	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvHeapObjectFree, traceHeapObjectID(addr))
   128  }
   129  
   130  // traceHeapObjectID creates a trace ID for a heap object at address addr.
   131  func traceHeapObjectID(addr uintptr) traceArg {
   132  	return traceArg(uint64(addr)-trace.minPageHeapAddr) / minHeapAlign
   133  }
   134  
   135  // GoroutineStackExists records that a goroutine stack already exists at address base with the provided size.
   136  func (tl traceLocker) GoroutineStackExists(base, size uintptr) {
   137  	order := traceCompressStackSize(size)
   138  	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGoroutineStack, traceGoroutineStackID(base), order)
   139  }
   140  
   141  // GoroutineStackAlloc records that a goroutine stack was newly allocated at address base with the provided size..
   142  func (tl traceLocker) GoroutineStackAlloc(base, size uintptr) {
   143  	order := traceCompressStackSize(size)
   144  	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGoroutineStackAlloc, traceGoroutineStackID(base), order)
   145  }
   146  
   147  // GoroutineStackFree records that a goroutine stack at address base is about to be freed.
   148  func (tl traceLocker) GoroutineStackFree(base uintptr) {
   149  	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGoroutineStackFree, traceGoroutineStackID(base))
   150  }
   151  
   152  // traceGoroutineStackID creates a trace ID for the goroutine stack from its base address.
   153  func traceGoroutineStackID(base uintptr) traceArg {
   154  	return traceArg(uint64(base)-trace.minPageHeapAddr) / fixedStack
   155  }
   156  
   157  // traceCompressStackSize assumes size is a power of 2 and returns log2(size).
   158  func traceCompressStackSize(size uintptr) traceArg {
   159  	if size&(size-1) != 0 {
   160  		throw("goroutine stack size is not a power of 2")
   161  	}
   162  	return traceArg(sys.Len64(uint64(size)))
   163  }
   164
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