gecko-dev/xpcom/base/nsIMemoryReporter.idl

/* -*- Mode: C++; tab-width: 50; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"

interface nsISimpleEnumerator;
interface nsIRunnable;
interface nsICancelableRunnable;

/*
 * Memory reporters measure Firefox's memory usage.  They are mainly used to
 * generate the about:memory page.  You should read
 * https://wiki.mozilla.org/Memory_Reporting before writing a memory
 * reporter.
 */

/*
 * An nsIMemoryReporter reports a single memory measurement as an object.
 * Use this when it makes sense to gather this measurement without gathering
 * related measurements at the same time.
 *
 * Note that the |amount| field may be implemented as a function, and so
 * accessing it can trigger significant computation;  the other fields can
 * be accessed without triggering this computation.  (Compare and contrast
 * this with nsIMemoryMultiReporter.)  
 *
 * aboutMemory.js is the most important consumer of memory reports.  It
 * places the following constraints on reports.
 *
 * - There must be an "explicit" tree.  It represents non-overlapping
 *   regions of memory that have been explicitly allocated with an
 *   OS-level allocation (e.g. mmap/VirtualAlloc/vm_allocate) or a
 *   heap-level allocation (e.g. malloc/calloc/operator new).  Reporters
 *   in this tree must have kind HEAP or NONHEAP, units BYTES, and a
 *   description that is a sentence (i.e. starts with a capital letter and
 *   ends with a period, or similar).
 *
 * - The "size", "rss", "pss" and "swap" trees are optional.  They
 *   represent regions of virtual memory that the process has mapped.
 *   Reporters in this category must have kind NONHEAP, units BYTES, and a
 *   non-empty description.
 *
 * - The "compartments" and "ghost-windows" trees are optional.  They are
 *   used by about:compartments.  Reporters in these trees must have kind
 *   OTHER, units COUNT, an amount of 1, and a description that's an empty
 *   string.
 *
 * - All other reports are unconstrained except that they must have a
 *   description that is a sentence.
 */
[scriptable, uuid(b2c39f65-1799-4b92-a806-ab3cf6af3cfa)]
interface nsIMemoryReporter : nsISupports
{
  /*
   * The name of the process containing this reporter.  Each reporter initially
   * has "" in this field, indicating that it applies to the current process.
   * (This is true even for reporters in a child process.)  When a reporter
   * from a child process is copied into the main process, the copy has its
   * 'process' field set appropriately.
   */
  readonly attribute ACString process;

  /*
   * The path that this memory usage should be reported under.  Paths are
   * '/'-delimited, eg. "a/b/c".  
   *
   * Each reporter can be viewed as representing a leaf node in a tree.
   * Internal nodes of the tree don't have reporters.  So, for example, the
   * reporters "explicit/a/b", "explicit/a/c", "explicit/d/e", and
   * "explicit/d/f" define this tree:
   *
   *   explicit
   *   |--a
   *   |  |--b [*]
   *   |  \--c [*]
   *   \--d
   *      |--e [*]
   *      \--f [*]
   *
   * Nodes marked with a [*] have a reporter.  Notice that the internal
   * nodes are implicitly defined by the paths.
   *
   * Nodes within a tree should not overlap measurements, otherwise the
   * parent node measurements will be double-counted.  So in the example
   * above, |b| should not count any allocations counted by |c|, and vice
   * versa.
   *
   * All nodes within each tree must have the same units.
   *
   * If you want to include a '/' not as a path separator, e.g. because the
   * path contains a URL, you need to convert each '/' in the URL to a '\'.
   * Consumers of the path will undo this change.  Any other '\' character
   * in a path will also be changed.  This is clumsy but hasn't caused any
   * problems so far.
   *
   * The paths of all reporters form a set of trees.  Trees can be
   * "degenerate", i.e. contain a single entry with no '/'.
   */
  readonly attribute AUTF8String path;

  /*
   * There are three kinds of memory reporters.
   *
   *  - HEAP: reporters measuring memory allocated by the heap allocator,
   *    e.g. by calling malloc, calloc, realloc, memalign, operator new, or
   *    operator new[].  Reporters in this category must have units
   *    UNITS_BYTES.
   *
   *  - NONHEAP: reporters measuring memory which the program explicitly
   *    allocated, but does not live on the heap.  Such memory is commonly
   *    allocated by calling one of the OS's memory-mapping functions (e.g.
   *    mmap, VirtualAlloc, or vm_allocate).  Reporters in this category
   *    must have units UNITS_BYTES.
   *
   *  - OTHER: reporters which don't fit into either of these categories.
   *    They can have any units.
   *
   * The kind only matters for reporters in the "explicit" tree;
   * aboutMemory.js uses it to calculate "heap-unclassified".
   */
  const int32_t KIND_NONHEAP = 0;
  const int32_t KIND_HEAP    = 1;
  const int32_t KIND_OTHER   = 2;

  /*
   * The reporter kind.  See KIND_* above.
   */
  readonly attribute int32_t kind;

  /*
   * The amount reported by a memory reporter must have one of the following
   * units, but you may of course add new units as necessary:
   *
   *  - BYTES: The amount contains a number of bytes.
   *
   *  - COUNT: The amount is an instantaneous count of things currently in
   *    existence.  For instance, the number of tabs currently open would have
   *    units COUNT.
   *
   *  - COUNT_CUMULATIVE: The amount contains the number of times some event
   *    has occurred since the application started up.  For instance, the
   *    number of times the user has opened a new tab would have units
   *    COUNT_CUMULATIVE.
   *
   *    The amount returned by a reporter with units COUNT_CUMULATIVE must
   *    never decrease over the lifetime of the application.
   *
   *  - PERCENTAGE: The amount contains a fraction that should be expressed as
   *    a percentage.  NOTE!  The |amount| field should be given a value 100x
   *    the actual percentage;  this number will be divided by 100 when shown.
   *    This allows a fractional percentage to be shown even though |amount| is
   *    an integer.  E.g. if the actual percentage is 12.34%, |amount| should
   *    be 1234.
   *
   *    Values greater than 100% are allowed.
   */
  const int32_t UNITS_BYTES = 0;
  const int32_t UNITS_COUNT = 1;
  const int32_t UNITS_COUNT_CUMULATIVE = 2;
  const int32_t UNITS_PERCENTAGE = 3;

  /*
   * The units on the reporter's amount.  See UNITS_* above.
   */
  readonly attribute int32_t units;

  /*
   * The numeric value reported by this memory reporter.  Accesses can fail if
   * something goes wrong when getting the amount.
   */
  readonly attribute int64_t amount;

  /*
   * A human-readable description of this memory usage report.
   */
  readonly attribute AUTF8String description;
};

[scriptable, function, uuid(5b15f3fa-ba15-443c-8337-7770f5f0ce5d)]
interface nsIMemoryMultiReporterCallback : nsISupports
{
  void callback(in ACString process, in AUTF8String path, in int32_t kind,
                in int32_t units, in int64_t amount,
                in AUTF8String description, in nsISupports closure);
};

/*
 * An nsIMemoryMultiReporter reports multiple memory measurements via a
 * callback function which is called once for each measurement.  Use this
 * when you want to gather multiple measurements in a single operation (eg.
 * a single traversal of a large data structure).
 *
 * The arguments to the callback deliberately match the fields in
 * nsIMemoryReporter, but note that seeing any of these arguments requires
 * calling collectReports which will trigger all relevant computation.
 * (Compare and contrast this with nsIMemoryReporter, which allows all
 * fields except |amount| to be accessed without triggering computation.)
 */
[scriptable, uuid(61d498d5-b460-4398-a8ea-7f75208534b4)]
interface nsIMemoryMultiReporter : nsISupports
{
  /*
   * The name of the multi-reporter.  Useful when only one multi-reporter
   * needs to be run.  Must be unique;  if multi-reporters share names it's
   * likely the wrong one will be called in certain circumstances.
   */
  readonly attribute ACString name;

  /*
   * Run the multi-reporter.
   */
  void collectReports(in nsIMemoryMultiReporterCallback callback,
                      in nsISupports closure);

  /*
   * Return the sum of all this multi-reporter's measurements that have a
   * path that starts with "explicit" and are KIND_NONHEAP.
   *
   * This is a hack that's required to implement
   * nsIMemoryReporterManager::explicit efficiently, which is important --
   * multi-reporters can special-case this operation so it's much faster
   * than getting all the reports, filtering out the unneeded ones, and
   * summing the remainder.
   */
  readonly attribute int64_t explicitNonHeap;
};

[scriptable, builtinclass, uuid(0baaa958-3112-4952-b557-2a0c57eabb8f)]
interface nsIMemoryReporterManager : nsISupports
{
  /*
   * Return an enumerator of nsIMemoryReporters that are currently registered.
   */
  nsISimpleEnumerator enumerateReporters ();

  /*
   * Return an enumerator of nsIMemoryMultiReporters that are currently
   * registered.
   */
  nsISimpleEnumerator enumerateMultiReporters ();

  /*
   * Register the given nsIMemoryReporter.  After a reporter is registered,
   * it will be available via enumerateReporters().  The Manager service
   * will hold a strong reference to the given reporter.
   */
  void registerReporter (in nsIMemoryReporter reporter);

  /*
   * Register the given nsIMemoryMultiReporter.  After a multi-reporter is
   * registered, it will be available via enumerateMultiReporters().  The
   * Manager service will hold a strong reference to the given
   * multi-reporter.
   */
  void registerMultiReporter (in nsIMemoryMultiReporter reporter);

  /*
   * Unregister the given memory reporter.
   */
  void unregisterReporter (in nsIMemoryReporter reporter);

  /*
   * Unregister the given memory multi-reporter.
   */
  void unregisterMultiReporter (in nsIMemoryMultiReporter reporter);

  /*
   * Initialize.
   */
  void init ();

  /*
   * Get the resident size (aka. RSS, physical memory used).  This reporter
   * is special-cased because it's interesting, is available on all
   * platforms, and returns a meaningful result on all common platforms.
   * Accesses can fail.
   */
  readonly attribute int64_t resident;

  /*
   * Get the total size of explicit memory allocations, both at the OS-level
   * (eg. via mmap, VirtualAlloc) and at the heap level (eg. via malloc,
   * calloc, operator new).  (Nb: it covers all heap allocations, but will
   * miss any OS-level ones not covered by memory reporters.)  This reporter
   * is special-cased because it's interesting, and is moderately difficult
   * to compute in JS.  Accesses can fail.
   */
  readonly attribute int64_t explicit;

  /*
   * This attribute indicates if moz_malloc_usable_size() works.
   */
  [infallible] readonly attribute boolean hasMozMallocUsableSize;

  /*
   * Run a series of GC/CC's in an attempt to minimize the application's memory
   * usage.  When we're finished, we invoke the given runnable if it's not
   * null.  Returns a reference to the runnable used for carrying out the task.
   */
  nsICancelableRunnable minimizeMemoryUsage(in nsIRunnable callback);
};

%{C++

/*
 * Note that this defaults 'process' to "", which is usually what's desired.
 */
#define NS_MEMORY_REPORTER_IMPLEMENT_HELPER(_classname, _path, _kind, _units, _amountFunction, _desc, _ts) \
    class MemoryReporter_##_classname MOZ_FINAL : public nsIMemoryReporter {                  \
    public:                                                                                   \
      NS_DECL_ISUPPORTS                                                                       \
      NS_IMETHOD GetProcess(nsACString &process) { process.Truncate(); return NS_OK; }        \
      NS_IMETHOD GetPath(nsACString &memoryPath) { memoryPath.AssignLiteral(_path); return NS_OK; }  \
      NS_IMETHOD GetKind(int *kind) { *kind = _kind; return NS_OK; }                          \
      NS_IMETHOD GetUnits(int *units) { *units = _units; return NS_OK; }                      \
      NS_IMETHOD GetAmount(int64_t *amount) { *amount = _amountFunction(); return NS_OK; }    \
      NS_IMETHOD GetDescription(nsACString &desc) { desc.AssignLiteral(_desc); return NS_OK; }       \
    };                                                                                        \
    NS_IMPL##_ts##ISUPPORTS1(MemoryReporter_##_classname, nsIMemoryReporter)

/*
 * The only difference between this and NS_MEMORY_REPORTER_IMPLEMENT_HELPER
 * is that the function used to implement GetAmount is fallible.
 */
#define NS_FALLIBLE_MEMORY_REPORTER_IMPLEMENT_HELPER(_classname, _path, _kind, _units, _amountFunction, _desc, _ts) \
    class MemoryReporter_##_classname MOZ_FINAL : public nsIMemoryReporter {                  \
    public:                                                                                   \
      NS_DECL_ISUPPORTS                                                                       \
      NS_IMETHOD GetProcess(nsACString &process) { process.Truncate(); return NS_OK; }        \
      NS_IMETHOD GetPath(nsACString &memoryPath) { memoryPath.AssignLiteral(_path); return NS_OK; }  \
      NS_IMETHOD GetKind(int *kind) { *kind = _kind; return NS_OK; }                          \
      NS_IMETHOD GetUnits(int *units) { *units = _units; return NS_OK; }                      \
      NS_IMETHOD GetAmount(int64_t *amount) { return _amountFunction(amount); }               \
      NS_IMETHOD GetDescription(nsACString &desc) { desc.AssignLiteral(_desc); return NS_OK; }       \
    };                                                                                        \
    NS_IMPL##_ts##ISUPPORTS1(MemoryReporter_##_classname, nsIMemoryReporter)

#define NS_MEMORY_REPORTER_IMPLEMENT(_c, _p, _k, _u, _a, _d) \
        NS_MEMORY_REPORTER_IMPLEMENT_HELPER(_c, _p, _k, _u, _a, _d, _)
#define NS_THREADSAFE_MEMORY_REPORTER_IMPLEMENT(_c, _p, _k, _u, _a, _d) \
        NS_MEMORY_REPORTER_IMPLEMENT_HELPER(_c, _p, _k, _u, _a, _d, _THREADSAFE_)
#define NS_FALLIBLE_MEMORY_REPORTER_IMPLEMENT(_c, _p, _k, _u, _a, _d) \
        NS_FALLIBLE_MEMORY_REPORTER_IMPLEMENT_HELPER(_c, _p, _k, _u, _a, _d, _)
#define NS_FALLIBLE_THREADSAFE_MEMORY_REPORTER_IMPLEMENT(_c, _p, _k, _u, _a, _d) \
        NS_FALLIBLE_MEMORY_REPORTER_IMPLEMENT_HELPER(_c, _p, _k, _u, _a, _d, _THREADSAFE_)

#define NS_MEMORY_REPORTER_NAME(_classname)  MemoryReporter_##_classname

// Note that the memory reporters are held in an nsCOMArray, which means
// that individual reporters should be referenced with |nsIMemoryReporter *|
// instead of nsCOMPtr<nsIMemoryReporter>.

nsresult NS_RegisterMemoryReporter(nsIMemoryReporter *reporter);
nsresult NS_RegisterMemoryMultiReporter(nsIMemoryMultiReporter *reporter);

nsresult NS_UnregisterMemoryReporter(nsIMemoryReporter *reporter);
nsresult NS_UnregisterMemoryMultiReporter(nsIMemoryMultiReporter *reporter);

#if defined(MOZ_DMD)
namespace mozilla {
namespace dmd {
// This runs all the memory reporters but does nothing with the results;  i.e.
// it does the minimal amount of work possible for DMD to do its thing.
void RunReporters();
}
}
#endif  // defined(MOZ_DMD)

#if defined(MOZ_DMD)

#if !defined(MOZ_MEMORY)
#error "MOZ_DMD requires MOZ_MEMORY"
#endif

#include "DMD.h"

#define MOZ_REPORT(ptr)          mozilla::dmd::Report(ptr)
#define MOZ_REPORT_ON_ALLOC(ptr) mozilla::dmd::ReportOnAlloc(ptr)

#else

#define MOZ_REPORT(ptr)
#define MOZ_REPORT_ON_ALLOC(ptr)

#endif  // defined(MOZ_DMD)

// Functions generated via this macro should be used by all traversal-based
// memory reporters.  Such functions return |moz_malloc_size_of(ptr)|;  this
// will always be zero on some obscure platforms.
//
// You might be wondering why we have a macro that creates multiple functions
// that differ only in their name, instead of a single
// MemoryReporterMallocSizeOf function.  It's mostly to help with DMD
// integration, though it sometimes also helps with debugging and temporary ad
// hoc profiling.  The function name chosen doesn't matter greatly, but it's
// best to make it similar to the path used by the relevant memory
// reporter(s).
#define NS_MEMORY_REPORTER_MALLOC_SIZEOF_FUN(fn)                              \
  static size_t fn(const void *ptr)                                           \
  {                                                                           \
      MOZ_REPORT(ptr);                                                        \
      return moz_malloc_size_of(ptr);                                         \
  }

// Functions generated by the next two macros should be used by wrapping
// allocators that report heap blocks as soon as they are allocated and
// unreport them as soon as they are freed.  Such allocators are used in cases
// where we have third-party code that we cannot modify.  The two functions
// must always be used in tandem.
#define NS_MEMORY_REPORTER_MALLOC_SIZEOF_ON_ALLOC_FUN(fn)                     \
  static size_t fn(const void *ptr)                                           \
  {                                                                           \
      MOZ_REPORT_ON_ALLOC(ptr);                                               \
      return moz_malloc_size_of(ptr);                                         \
  }
#define NS_MEMORY_REPORTER_MALLOC_SIZEOF_ON_FREE_FUN(fn)                      \
  static size_t fn(const void *ptr)                                           \
  {                                                                           \
      return moz_malloc_size_of(ptr);                                         \
  }

%}