public void GCRootsIndirectHandles()
{
using DataTarget dataTarget = TestTargets.GCRoot2.LoadFullDump();
ClrRuntime runtime = dataTarget.ClrVersions.Single().CreateRuntime();
ClrHeap heap = runtime.Heap;
GCRoot gcroot = new GCRoot(heap);
ulong target = heap.GetObjectsOfType("IndirectTarget").Single();
_ = Assert.Single(gcroot.EnumerateGCRoots(target, unique: true, CancellationToken.None));
Assert.Equal(2, gcroot.EnumerateGCRoots(target, unique: false, CancellationToken.None).Count());
}
private void GCRootsImpl(GCRoot gcroot)
{
ClrHeap heap = gcroot.Heap;
ulong target = heap.GetObjectsOfType("TargetType").Single();
RootPath[] rootPaths = gcroot.EnumerateGCRoots(target, false, CancellationToken.None).ToArray();
Assert.IsTrue(rootPaths.Length >= 2);
foreach (RootPath rootPath in rootPaths)
{
AssertPathIsCorrect(heap, rootPath.Path.ToArray(), rootPath.Path.First().Address, target);
}
bool hasThread = false, hasStatic = false;
foreach (RootPath rootPath in rootPaths)
{
if (rootPath.Root.Kind == GCRootKind.Pinning)
{
hasStatic = true;
}
else if (rootPath.Root.Kind == GCRootKind.LocalVar)
{
hasThread = true;
}
}
Assert.IsTrue(hasThread);
Assert.IsTrue(hasStatic);
}
private void GCRootsImpl(GCRoot gcroot, ClrHeap heap, ulong target, int parallelism, bool unique)
{
GCRootPath[] rootPaths = gcroot.EnumerateGCRoots(target, unique: unique, parallelism, CancellationToken.None).ToArray();
// In the case where we say we only want unique rooting chains AND we want to look in parallel,
// we cannot guarantee that we will pick the static roots over the stack ones. Hence we don't
// ensure that the static variable is enumerated when unique == true.
CheckRootPaths(heap, target, rootPaths, mustContainStatic: !unique);
}
/// <summary>
///
/// </summary>
/// <param name="objects"></param>
/// <param name="topn"></param>
/// <returns></returns>
private IEnumerable <(string objectAddress, string GCRoot)> GetGCRoot
(IEnumerable <ClrObject> objects, int topn = 3)
{
GCRoot gCRoot = new GCRoot(Runtime.Heap);
var topObjs = objects.Take(topn);
return(topObjs.Select(o => (objectAddress: o.Address.ToString(),
GCRoot: gCRoot.EnumerateGCRoots(o, false, Environment.ProcessorCount).First().ToString())));
}
private void GCStaticRootsImpl(GCRoot gcroot)
{
ulong target = gcroot.Heap.GetObjectsOfType("TargetType").Single();
RootPath[] paths = gcroot.EnumerateGCRoots(target, false, CancellationToken.None).ToArray();
Assert.AreEqual(1, paths.Length);
RootPath rootPath = paths[0];
AssertPathIsCorrect(gcroot.Heap, rootPath.Path.ToArray(), rootPath.Path.First().Address, target);
}
private void GCRootsImpl(GCRoot gcroot)
{
ClrHeap heap = gcroot.Heap;
ulong target = heap.GetObjectsOfType("TargetType").Single();
GCRootPath[] rootPaths = gcroot.EnumerateGCRoots(target, unique: false, 1, CancellationToken.None).ToArray();
CheckRootPaths(heap, target, rootPaths, mustContainStatic: true);
rootPaths = gcroot.EnumerateGCRoots(target, unique: false, 16, CancellationToken.None).ToArray();
CheckRootPaths(heap, target, rootPaths, mustContainStatic: true);
rootPaths = gcroot.EnumerateGCRoots(target, unique: true, 1, CancellationToken.None).ToArray();
CheckRootPaths(heap, target, rootPaths, mustContainStatic: true);
// In the case where we say we only want unique rooting chains AND we want to look in parallel,
// we cannot guarantee that we will pick the static roots over the stack ones. Hence we don't
// ensure that the static variable is enumerated.
rootPaths = gcroot.EnumerateGCRoots(target, unique: true, 16, CancellationToken.None).ToArray();
CheckRootPaths(heap, target, rootPaths, mustContainStatic: false);
}
public IEnumerable <dynamic> ExtractData(ClrRuntime clr, Action <string> actionLog = null)
{
if (!clr.Heap.CanWalkHeap)
{
throw new InvalidOperationException("Cannot extract gc roots, heap is not in a walkable state");
}
var gcRootHandle = new GCRoot(clr.Heap);
var currentObjectName = string.Empty;
try
{
gcRootHandle.ProgressUpdated += ReportGcRootEnumerationProgress;
foreach (var obj in clr.Heap.EnumerateObjects())
{
if (obj.Type == null)
{
continue;
}
currentObjectName = $"{obj.Type.Name} - #{obj.Address}";
actionLog?.Invoke($"Enumerating roots for ${currentObjectName}");
foreach (var rootPath in gcRootHandle.EnumerateGCRoots(obj.Address, true, Environment.ProcessorCount))
{
yield return(AutoMapper.Instance.Map <GcRoot>(rootPath,
opts => opts.AfterMap((_, dst) => {
var segment = clr.Heap.GetSegmentByAddress(rootPath.Root.Object);
dst.Generation = segment.GetGeneration(rootPath.Root.Object.Address);
})));
}
}
}
finally
{
gcRootHandle.ProgressUpdated -= ReportGcRootEnumerationProgress;
}
void ReportGcRootEnumerationProgress(GCRoot source, long processed) =>
actionLog?.Invoke($"Finding GC Roots for {currentObjectName}: {processed} objects processed.");
}
public void EnumerateGCRootsCancel()
{
using (DataTarget dataTarget = TestTargets.GCRoot.LoadFullDump())
{
ClrRuntime runtime = dataTarget.ClrVersions.Single().CreateRuntime();
ClrHeap heap = runtime.Heap;
heap.StackwalkPolicy = ClrRootStackwalkPolicy.SkipStack;
GCRoot gcroot = new GCRoot(runtime.Heap);
ulong target = gcroot.Heap.GetObjectsOfType("TargetType").Single();
CancellationTokenSource source = new CancellationTokenSource();
source.Cancel();
try
{
gcroot.EnumerateGCRoots(target, false, source.Token).ToArray();
Assert.Fail("Should have been cancelled!");
}
catch (OperationCanceledException)
{
}
}
}
public static void Main(string[] args)
{
ulong target = 0;
if (args.Length != 2)
{
PrintUsage();
Environment.Exit(1);
}
else if (!File.Exists(args[0]))
{
PrintUsage();
Console.WriteLine($"File not found: '{args[0]}'.");
Environment.Exit(1);
}
else if (!ulong.TryParse(args[1], System.Globalization.NumberStyles.HexNumber, null, out target))
{
PrintUsage();
Console.WriteLine($"Could not parse object address '{args[1]}'.");
Environment.Exit(1);
}
using DataTarget dt = DataTarget.LoadDump(args[0]);
using ClrRuntime runtime = dt.ClrVersions.Single().CreateRuntime();
ClrHeap heap = runtime.Heap;
/* At the most basic level, to implement !gcroot, simply create a GCRoot object. Then call
* EnumerateGCRoots to find unique paths from the root to the target object. This runs similarly
* to !gcroot. Please note you will receive all paths each time this code is run, but the order
* of roots from run to run are NOT guaranteed. Note that all operations take a cancellation token
* which you can use to cancel GCRoot at any time (it will throw an OperationCancelledException).
*/
GCRoot gcroot = new GCRoot(heap);
foreach (GCRootPath rootPath in gcroot.EnumerateGCRoots(target))
{
Console.Write($"{rootPath.Root} -> ");
Console.WriteLine(string.Join(" -> ", rootPath.Path.Select(obj => obj.Address)));
}
Console.WriteLine();
// ==========================================
/* Since GCRoot can take a long time to run, ClrMD provides an event to get progress updates on how far
* along GCRoot is.
*/
gcroot.ProgressUpdated += (GCRoot source, int current) =>
{
Console.WriteLine($"Current root {source} objects inspected={current:n0}");
};
// ==========================================
/* GCRoot can use parallel processing to use more of the CPU and work in parallel. This is done
* automatically (and is on by default)...but only if you use .BuildCache and build the *complete* GC heap
* in local memory. Since limitations in ClrMD and the APIs it's built on do not allow multithreading,
* we only do multithreaded processing if we never need to call into ClrMD while walking objects.
*
* One downside is that multithreaded processing means the order of roots enumerated is not stable from
* run to run. You can turn off multithreaded processing so that the results of GCRoot are stable between
* runs (though slower to run), but GCRoot makes NO guarantees about the order of roots you receive, and
* they may change from build to build of ClrMD or change depending on the other flags set on the GCRoot
* object.
*/
// This can be used to turn off multithreaded processing, this property is true by default:
// gcroot.AllowParallelSearch = false;
// ==========================================
/* Finally, we will run through the enumeration one more time, but this time using parallel processing
* and printing out a bunch of status messages for demonstration.
*/
Console.WriteLine("Get ready for a lot of output, since we are raw printing status updates!");
Console.WriteLine();
foreach (GCRootPath rootPath in gcroot.EnumerateGCRoots(target, false, Environment.ProcessorCount))
{
Console.Write($"{rootPath.Root} -> ");
Console.WriteLine(string.Join(" -> ", rootPath.Path.Select(obj => obj.Address)));
}
}
static void Main()
{
Helpers.TestWorkingDirectory = Environment.CurrentDirectory;
// Please see src\Microsoft.Diagnostics.Runtime.Tests\Targets\GCRoot.cs for the debuggee we
// are currently debugging.
DataTarget dt = TestTargets.GCRoot.LoadFullDump();
ClrRuntime runtime = dt.ClrVersions.Single().CreateRuntime();
ClrHeap heap = runtime.Heap;
// This is the object we are looking for. Let's say the address is 0x1234. The following
// demo will show you how to build output similar to SOS's "!gcroot 0x1234".
ulong target = GetTarget(heap);
/* At the most basic level, to implement !gcroot, simply create a GCRoot object. Then call
* EnumerateGCRoots to find unique paths from the root to the target object. This runs similarly
* to !gcroot. Please note you will receive all paths each time this code is run, but the order
* of roots from run to run are NOT guaranteed. Note that all operations take a cancellation token
* which you can use to cancel GCRoot at any time (it will throw an OperationCancelledException).
*/
GCRoot gcroot = new GCRoot(heap);
foreach (GCRootPath rootPath in gcroot.EnumerateGCRoots(target, CancellationToken.None))
{
Console.Write($"{rootPath.Root} -> ");
Console.WriteLine(string.Join(" -> ", rootPath.Path.Select(obj => obj.Address)));
}
Console.WriteLine();
// ==========================================
/* Since GCRoot can take a long time to run, ClrMD provides an event to get progress updates on how far
* along GCRoot is. There are some caveats here, in that you only get updates if you have cached the
* gc heap locally (more on that later). This is because without pre-fetching and compiling data ahead
* of time, we have no real way to know how many objects are on the heap. The intent of this delegate is
* to allow you to report to the user a rough percentage of how far along things are (such as a progress
* bar or console output).
*/
gcroot.ProgressUpdated += delegate(GCRoot source, long current, long total)
{
// Note that sometimes we don't know how many total items will be processed in the current
// phase. In that case, total will be -1. (For example, we don't know the total number
// of handles on the handle table until we enumerate them all.)
if (total > 0)
{
Console.WriteLine($"heap searched={(int)(100 * current / (float)total)}%");
}
else
{
Console.WriteLine($"objects inspected={current}");
}
};
// ==========================================
/* The next important concept is that GCRoot allows you to trade memory for a faster !gcroot.
* Due to how memory reads and the clr debugging layer are written, it can take 30-60 minutes
* to run the full GCRoot algorithm on large dumps using the code above! To fix that, ClrMD
* allows you to copy all relevant data into local memory, at which point all GCRoot runs should
* complete very fast. Even the worst crash dumps should take <60 seconds to complete. The
* downside is this will use a lot of memory (in some cases, multiple gigs of memory), so you have
* to wrap the cach function in a try/catch for OOM exceptions.
*/
try
{
gcroot.BuildCache(CancellationToken.None);
// Now GCRoot will run MUCH, MUCH faster for the following code.
}
catch (OutOfMemoryException)
{
// Whoops, the crash dump in question was too big to read all data into memory. We will continue
// on without cached GC data.
}
// ==========================================
/* The next thing to know about GCRoot is there are two ways we can walk the stack of threads looking for
* roots: Exact and Fast. You change this setting with ClrHeap.StackwalkPolicy. Using a stackwalk policy
* of exact will show you exactly what the GC sees, eliminating false roots, but it can be slow. Using the
* Fast stackwalk policy is very fast, but can over-report roots that are actually just old GC references
* left on the stack.
* Unfortunately due to the way that CLR's debugging layer is implemented, using Exact can take a *long*
* time (10s of minutes if the dump has 1000s of threads). The default is to let ClrMD decide which policy
* to use. Lastly, note that you can choose to omit stack roots entirely by setting StackwalkPolicy to
* "SkipStack".
*/
// Let's set a concrete example:
heap.StackwalkPolicy = ClrRootStackwalkPolicy.Exact;
// ==========================================
/* Finally, GCRoot can use parallel processing to use more of the CPU and work in parallel. This is done
* automatically (and is on by default)...but only if you use .BuildCache and build the *complete* GC heap
* in local memory. Since limitations in ClrMD and the APIs it's built on do not allow multithreading,
* we only do multithreaded processing if we never need to call into ClrMD while walking objects.
*
* One downside is that multithreaded processing means the order of roots enumerated is not stable from
* run to run. You can turn off multithreaded processing so that the results of GCRoot are stable between
* runs (though slower to run), but GCRoot makes NO guarantees about the order of roots you receive, and
* they may change from build to build of ClrMD or change depending on the other flags set on the GCRoot
* object.
*/
// This can be used to turn off multithreaded processing, this property is true by default:
// gcroot.AllowParallelSearch = false;
// You can set the maximum number of tasks using this. The default is Environment.ProcessorCount * 2:
gcroot.MaximumTasksAllowed = 20;
// ==========================================
/* Finally, we will run through the enumeration one more time, but this time using parallel processing
* and printing out a bunch of status messages for demonstration.
*/
Console.WriteLine("Get ready for a lot of output, since we are raw printing status updates!");
Console.WriteLine();
foreach (GCRootPath rootPath in gcroot.EnumerateGCRoots(target, CancellationToken.None))
{
Console.Write($"{rootPath.Root} -> ");
Console.WriteLine(string.Join(" -> ", rootPath.Path.Select(obj => obj.Address)));
}
}
/// <summary> /// Enumerates GCRoots of a given object. Similar to !gcroot. Note this function only returns paths that are fully /// unique. /// </summary> /// <param name="target">The target object to search for GC rooting.</param> /// <param name="cancelToken">A cancellation token to stop enumeration.</param> /// <returns>An enumeration of all GC roots found for target.</returns> /// <inheritdoc /> public IEnumerable <IRootPath> EnumerateGCRoots(ulong target, CancellationToken cancelToken) => Root.EnumerateGCRoots(target, cancelToken).Select(Converter.Convert);