michael@0: // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
michael@0: // Use of this source code is governed by a BSD-style license that can be
michael@0: // found in the LICENSE file.
michael@0: 
michael@0: #include "base/stats_table.h"
michael@0: 
michael@0: #include "base/logging.h"
michael@0: #include "base/platform_thread.h"
michael@0: #include "base/process_util.h"
michael@0: #include "base/scoped_ptr.h"
michael@0: #include "base/shared_memory.h"
michael@0: #include "base/string_piece.h"
michael@0: #include "base/string_util.h"
michael@0: #include "base/sys_string_conversions.h"
michael@0: #include "base/thread_local_storage.h"
michael@0: 
michael@0: #if defined(OS_POSIX)
michael@0: #include "errno.h"
michael@0: #endif
michael@0: 
michael@0: // The StatsTable uses a shared memory segment that is laid out as follows
michael@0: //
michael@0: // +-------------------------------------------+
michael@0: // | Version | Size | MaxCounters | MaxThreads |
michael@0: // +-------------------------------------------+
michael@0: // | Thread names table                        |
michael@0: // +-------------------------------------------+
michael@0: // | Thread TID table                          |
michael@0: // +-------------------------------------------+
michael@0: // | Thread PID table                          |
michael@0: // +-------------------------------------------+
michael@0: // | Counter names table                       |
michael@0: // +-------------------------------------------+
michael@0: // | Data                                      |
michael@0: // +-------------------------------------------+
michael@0: //
michael@0: // The data layout is a grid, where the columns are the thread_ids and the
michael@0: // rows are the counter_ids.
michael@0: //
michael@0: // If the first character of the thread_name is '\0', then that column is
michael@0: // empty.
michael@0: // If the first character of the counter_name is '\0', then that row is
michael@0: // empty.
michael@0: //
michael@0: // About Locking:
michael@0: // This class is designed to be both multi-thread and multi-process safe.
michael@0: // Aside from initialization, this is done by partitioning the data which
michael@0: // each thread uses so that no locking is required.  However, to allocate
michael@0: // the rows and columns of the table to particular threads, locking is
michael@0: // required.
michael@0: //
michael@0: // At the shared-memory level, we have a lock.  This lock protects the
michael@0: // shared-memory table only, and is used when we create new counters (e.g.
michael@0: // use rows) or when we register new threads (e.g. use columns).  Reading
michael@0: // data from the table does not require any locking at the shared memory
michael@0: // level.
michael@0: //
michael@0: // Each process which accesses the table will create a StatsTable object.
michael@0: // The StatsTable maintains a hash table of the existing counters in the
michael@0: // table for faster lookup.  Since the hash table is process specific,
michael@0: // each process maintains its own cache.  We avoid complexity here by never
michael@0: // de-allocating from the hash table.  (Counters are dynamically added,
michael@0: // but not dynamically removed).
michael@0: 
michael@0: // In order for external viewers to be able to read our shared memory,
michael@0: // we all need to use the same size ints.
michael@0: COMPILE_ASSERT(sizeof(int)==4, expect_4_byte_ints);
michael@0: 
michael@0: namespace {
michael@0: 
michael@0: // An internal version in case we ever change the format of this
michael@0: // file, and so that we can identify our table.
michael@0: const int kTableVersion = 0x13131313;
michael@0: 
michael@0: // The name for un-named counters and threads in the table.
michael@0: const char kUnknownName[] = "<unknown>";
michael@0: 
michael@0: // Calculates delta to align an offset to the size of an int
michael@0: inline int AlignOffset(int offset) {
michael@0:   return (sizeof(int) - (offset % sizeof(int))) % sizeof(int);
michael@0: }
michael@0: 
michael@0: inline int AlignedSize(int size) {
michael@0:   return size + AlignOffset(size);
michael@0: }
michael@0: 
michael@0: // StatsTableTLSData carries the data stored in the TLS slots for the
michael@0: // StatsTable.  This is used so that we can properly cleanup when the
michael@0: // thread exits and return the table slot.
michael@0: //
michael@0: // Each thread that calls RegisterThread in the StatsTable will have
michael@0: // a StatsTableTLSData stored in its TLS.
michael@0: struct StatsTableTLSData {
michael@0:   StatsTable* table;
michael@0:   int slot;
michael@0: };
michael@0: 
michael@0: }  // namespace
michael@0: 
michael@0: // The StatsTablePrivate maintains convenience pointers into the
michael@0: // shared memory segment.  Use this class to keep the data structure
michael@0: // clean and accessible.
michael@0: class StatsTablePrivate {
michael@0:  public:
michael@0:   // Various header information contained in the memory mapped segment.
michael@0:   struct TableHeader {
michael@0:     int version;
michael@0:     int size;
michael@0:     int max_counters;
michael@0:     int max_threads;
michael@0:   };
michael@0: 
michael@0:   // Construct a new StatsTablePrivate based on expected size parameters, or
michael@0:   // return NULL on failure.
michael@0:   static StatsTablePrivate* New(const std::string& name, int size,
michael@0:                                 int max_threads, int max_counters);
michael@0: 
michael@0:   base::SharedMemory* shared_memory() { return &shared_memory_; }
michael@0: 
michael@0:   // Accessors for our header pointers
michael@0:   TableHeader* table_header() const { return table_header_; }
michael@0:   int version() const { return table_header_->version; }
michael@0:   int size() const { return table_header_->size; }
michael@0:   int max_counters() const { return table_header_->max_counters; }
michael@0:   int max_threads() const { return table_header_->max_threads; }
michael@0: 
michael@0:   // Accessors for our tables
michael@0:   char* thread_name(int slot_id) const {
michael@0:     return &thread_names_table_[
michael@0:       (slot_id-1) * (StatsTable::kMaxThreadNameLength)];
michael@0:   }
michael@0:   PlatformThreadId* thread_tid(int slot_id) const {
michael@0:     return &(thread_tid_table_[slot_id-1]);
michael@0:   }
michael@0:   int* thread_pid(int slot_id) const {
michael@0:     return &(thread_pid_table_[slot_id-1]);
michael@0:   }
michael@0:   char* counter_name(int counter_id) const {
michael@0:     return &counter_names_table_[
michael@0:       (counter_id-1) * (StatsTable::kMaxCounterNameLength)];
michael@0:   }
michael@0:   int* row(int counter_id) const {
michael@0:     return &data_table_[(counter_id-1) * max_threads()];
michael@0:   }
michael@0: 
michael@0:  private:
michael@0:   // Constructor is private because you should use New() instead.
michael@0:   StatsTablePrivate() {}
michael@0: 
michael@0:   // Initializes the table on first access.  Sets header values
michael@0:   // appropriately and zeroes all counters.
michael@0:   void InitializeTable(void* memory, int size, int max_counters,
michael@0:                        int max_threads);
michael@0: 
michael@0:   // Initializes our in-memory pointers into a pre-created StatsTable.
michael@0:   void ComputeMappedPointers(void* memory);
michael@0: 
michael@0:   base::SharedMemory shared_memory_;
michael@0:   TableHeader* table_header_;
michael@0:   char* thread_names_table_;
michael@0:   PlatformThreadId* thread_tid_table_;
michael@0:   int* thread_pid_table_;
michael@0:   char* counter_names_table_;
michael@0:   int* data_table_;
michael@0: };
michael@0: 
michael@0: // static
michael@0: StatsTablePrivate* StatsTablePrivate::New(const std::string& name,
michael@0:                                           int size,
michael@0:                                           int max_threads,
michael@0:                                           int max_counters) {
michael@0:   scoped_ptr<StatsTablePrivate> priv(new StatsTablePrivate());
michael@0:   if (!priv->shared_memory_.Create(name, false, true, size))
michael@0:     return NULL;
michael@0:   if (!priv->shared_memory_.Map(size))
michael@0:     return NULL;
michael@0:   void* memory = priv->shared_memory_.memory();
michael@0: 
michael@0:   TableHeader* header = static_cast<TableHeader*>(memory);
michael@0: 
michael@0:   // If the version does not match, then assume the table needs
michael@0:   // to be initialized.
michael@0:   if (header->version != kTableVersion)
michael@0:     priv->InitializeTable(memory, size, max_counters, max_threads);
michael@0: 
michael@0:   // We have a valid table, so compute our pointers.
michael@0:   priv->ComputeMappedPointers(memory);
michael@0: 
michael@0:   return priv.release();
michael@0: }
michael@0: 
michael@0: void StatsTablePrivate::InitializeTable(void* memory, int size,
michael@0:                                         int max_counters,
michael@0:                                         int max_threads) {
michael@0:   // Zero everything.
michael@0:   memset(memory, 0, size);
michael@0: 
michael@0:   // Initialize the header.
michael@0:   TableHeader* header = static_cast<TableHeader*>(memory);
michael@0:   header->version = kTableVersion;
michael@0:   header->size = size;
michael@0:   header->max_counters = max_counters;
michael@0:   header->max_threads = max_threads;
michael@0: }
michael@0: 
michael@0: void StatsTablePrivate::ComputeMappedPointers(void* memory) {
michael@0:   char* data = static_cast<char*>(memory);
michael@0:   int offset = 0;
michael@0: 
michael@0:   table_header_ = reinterpret_cast<TableHeader*>(data);
michael@0:   offset += sizeof(*table_header_);
michael@0:   offset += AlignOffset(offset);
michael@0: 
michael@0:   // Verify we're looking at a valid StatsTable.
michael@0:   DCHECK_EQ(table_header_->version, kTableVersion);
michael@0: 
michael@0:   thread_names_table_ = reinterpret_cast<char*>(data + offset);
michael@0:   offset += sizeof(char) *
michael@0:             max_threads() * StatsTable::kMaxThreadNameLength;
michael@0:   offset += AlignOffset(offset);
michael@0: 
michael@0:   thread_tid_table_ = reinterpret_cast<PlatformThreadId*>(data + offset);
michael@0:   offset += sizeof(int) * max_threads();
michael@0:   offset += AlignOffset(offset);
michael@0: 
michael@0:   thread_pid_table_ = reinterpret_cast<int*>(data + offset);
michael@0:   offset += sizeof(int) * max_threads();
michael@0:   offset += AlignOffset(offset);
michael@0: 
michael@0:   counter_names_table_ = reinterpret_cast<char*>(data + offset);
michael@0:   offset += sizeof(char) *
michael@0:             max_counters() * StatsTable::kMaxCounterNameLength;
michael@0:   offset += AlignOffset(offset);
michael@0: 
michael@0:   data_table_ = reinterpret_cast<int*>(data + offset);
michael@0:   offset += sizeof(int) * max_threads() * max_counters();
michael@0: 
michael@0:   DCHECK_EQ(offset, size());
michael@0: }
michael@0: 
michael@0: 
michael@0: 
michael@0: // We keep a singleton table which can be easily accessed.
michael@0: StatsTable* StatsTable::global_table_ = NULL;
michael@0: 
michael@0: StatsTable::StatsTable(const std::string& name, int max_threads,
michael@0:                        int max_counters)
michael@0:     : impl_(NULL),
michael@0:       tls_index_(SlotReturnFunction) {
michael@0:   int table_size =
michael@0:     AlignedSize(sizeof(StatsTablePrivate::TableHeader)) +
michael@0:     AlignedSize((max_counters * sizeof(char) * kMaxCounterNameLength)) +
michael@0:     AlignedSize((max_threads * sizeof(char) * kMaxThreadNameLength)) +
michael@0:     AlignedSize(max_threads * sizeof(int)) +
michael@0:     AlignedSize(max_threads * sizeof(int)) +
michael@0:     AlignedSize((sizeof(int) * (max_counters * max_threads)));
michael@0: 
michael@0:   impl_ = StatsTablePrivate::New(name, table_size, max_threads, max_counters);
michael@0: 
michael@0:   // TODO(port): clean up this error reporting.
michael@0: #if defined(OS_WIN)
michael@0:   if (!impl_)
michael@0:     CHROMIUM_LOG(ERROR) << "StatsTable did not initialize:" << GetLastError();
michael@0: #elif defined(OS_POSIX)
michael@0:   if (!impl_)
michael@0:     CHROMIUM_LOG(ERROR) << "StatsTable did not initialize:" << strerror(errno);
michael@0: #endif
michael@0: }
michael@0: 
michael@0: StatsTable::~StatsTable() {
michael@0:   // Before we tear down our copy of the table, be sure to
michael@0:   // unregister our thread.
michael@0:   UnregisterThread();
michael@0: 
michael@0:   // Return ThreadLocalStorage.  At this point, if any registered threads
michael@0:   // still exist, they cannot Unregister.
michael@0:   tls_index_.Free();
michael@0: 
michael@0:   // Cleanup our shared memory.
michael@0:   delete impl_;
michael@0: 
michael@0:   // If we are the global table, unregister ourselves.
michael@0:   if (global_table_ == this)
michael@0:     global_table_ = NULL;
michael@0: }
michael@0: 
michael@0: int StatsTable::RegisterThread(const std::string& name) {
michael@0:   int slot = 0;
michael@0: 
michael@0:   // Registering a thread requires that we lock the shared memory
michael@0:   // so that two threads don't grab the same slot.  Fortunately,
michael@0:   // thread creation shouldn't happen in inner loops.
michael@0:   {
michael@0:     base::SharedMemoryAutoLock lock(impl_->shared_memory());
michael@0:     slot = FindEmptyThread();
michael@0:     if (!slot) {
michael@0:       return 0;
michael@0:     }
michael@0: 
michael@0:     DCHECK(impl_);
michael@0: 
michael@0:     // We have space, so consume a column in the table.
michael@0:     std::string thread_name = name;
michael@0:     if (name.empty())
michael@0:       thread_name = kUnknownName;
michael@0:     base::strlcpy(impl_->thread_name(slot), thread_name.c_str(),
michael@0:                   kMaxThreadNameLength);
michael@0:     *(impl_->thread_tid(slot)) = PlatformThread::CurrentId();
michael@0:     *(impl_->thread_pid(slot)) = base::GetCurrentProcId();
michael@0:   }
michael@0: 
michael@0:   // Set our thread local storage.
michael@0:   StatsTableTLSData* data = new StatsTableTLSData;
michael@0:   data->table = this;
michael@0:   data->slot = slot;
michael@0:   tls_index_.Set(data);
michael@0:   return slot;
michael@0: }
michael@0: 
michael@0: StatsTableTLSData* StatsTable::GetTLSData() const {
michael@0:   StatsTableTLSData* data =
michael@0:     static_cast<StatsTableTLSData*>(tls_index_.Get());
michael@0:   if (!data)
michael@0:     return NULL;
michael@0: 
michael@0:   DCHECK(data->slot);
michael@0:   DCHECK_EQ(data->table, this);
michael@0:   return data;
michael@0: }
michael@0: 
michael@0: void StatsTable::UnregisterThread() {
michael@0:   UnregisterThread(GetTLSData());
michael@0: }
michael@0: 
michael@0: void StatsTable::UnregisterThread(StatsTableTLSData* data) {
michael@0:   if (!data)
michael@0:     return;
michael@0:   DCHECK(impl_);
michael@0: 
michael@0:   // Mark the slot free by zeroing out the thread name.
michael@0:   char* name = impl_->thread_name(data->slot);
michael@0:   *name = '\0';
michael@0: 
michael@0:   // Remove the calling thread's TLS so that it cannot use the slot.
michael@0:   tls_index_.Set(NULL);
michael@0:   delete data;
michael@0: }
michael@0: 
michael@0: void StatsTable::SlotReturnFunction(void* data) {
michael@0:   // This is called by the TLS destructor, which on some platforms has
michael@0:   // already cleared the TLS info, so use the tls_data argument
michael@0:   // rather than trying to fetch it ourselves.
michael@0:   StatsTableTLSData* tls_data = static_cast<StatsTableTLSData*>(data);
michael@0:   if (tls_data) {
michael@0:     DCHECK(tls_data->table);
michael@0:     tls_data->table->UnregisterThread(tls_data);
michael@0:   }
michael@0: }
michael@0: 
michael@0: int StatsTable::CountThreadsRegistered() const {
michael@0:   if (!impl_)
michael@0:     return 0;
michael@0: 
michael@0:   // Loop through the shared memory and count the threads that are active.
michael@0:   // We intentionally do not lock the table during the operation.
michael@0:   int count = 0;
michael@0:   for (int index = 1; index <= impl_->max_threads(); index++) {
michael@0:     char* name = impl_->thread_name(index);
michael@0:     if (*name != '\0')
michael@0:       count++;
michael@0:   }
michael@0:   return count;
michael@0: }
michael@0: 
michael@0: int StatsTable::GetSlot() const {
michael@0:   StatsTableTLSData* data = GetTLSData();
michael@0:   if (!data)
michael@0:     return 0;
michael@0:   return data->slot;
michael@0: }
michael@0: 
michael@0: int StatsTable::FindEmptyThread() const {
michael@0:   // Note: the API returns slots numbered from 1..N, although
michael@0:   // internally, the array is 0..N-1.  This is so that we can return
michael@0:   // zero as "not found".
michael@0:   //
michael@0:   // The reason for doing this is because the thread 'slot' is stored
michael@0:   // in TLS, which is always initialized to zero, not -1.  If 0 were
michael@0:   // returned as a valid slot number, it would be confused with the
michael@0:   // uninitialized state.
michael@0:   if (!impl_)
michael@0:     return 0;
michael@0: 
michael@0:   int index = 1;
michael@0:   for (; index <= impl_->max_threads(); index++) {
michael@0:     char* name = impl_->thread_name(index);
michael@0:     if (!*name)
michael@0:       break;
michael@0:   }
michael@0:   if (index > impl_->max_threads())
michael@0:     return 0;  // The table is full.
michael@0:   return index;
michael@0: }
michael@0: 
michael@0: int StatsTable::FindCounterOrEmptyRow(const std::string& name) const {
michael@0:   // Note: the API returns slots numbered from 1..N, although
michael@0:   // internally, the array is 0..N-1.  This is so that we can return
michael@0:   // zero as "not found".
michael@0:   //
michael@0:   // There isn't much reason for this other than to be consistent
michael@0:   // with the way we track columns for thread slots.  (See comments
michael@0:   // in FindEmptyThread for why it is done this way).
michael@0:   if (!impl_)
michael@0:     return 0;
michael@0: 
michael@0:   int free_slot = 0;
michael@0:   for (int index = 1; index <= impl_->max_counters(); index++) {
michael@0:     char* row_name = impl_->counter_name(index);
michael@0:     if (!*row_name && !free_slot)
michael@0:       free_slot = index;  // save that we found a free slot
michael@0:     else if (!strncmp(row_name, name.c_str(), kMaxCounterNameLength))
michael@0:       return index;
michael@0:   }
michael@0:   return free_slot;
michael@0: }
michael@0: 
michael@0: int StatsTable::FindCounter(const std::string& name) {
michael@0:   // Note: the API returns counters numbered from 1..N, although
michael@0:   // internally, the array is 0..N-1.  This is so that we can return
michael@0:   // zero as "not found".
michael@0:   if (!impl_)
michael@0:     return 0;
michael@0: 
michael@0:   // Create a scope for our auto-lock.
michael@0:   {
michael@0:     AutoLock scoped_lock(counters_lock_);
michael@0: 
michael@0:     // Attempt to find the counter.
michael@0:     CountersMap::const_iterator iter;
michael@0:     iter = counters_.find(name);
michael@0:     if (iter != counters_.end())
michael@0:       return iter->second;
michael@0:   }
michael@0: 
michael@0:   // Counter does not exist, so add it.
michael@0:   return AddCounter(name);
michael@0: }
michael@0: 
michael@0: int StatsTable::AddCounter(const std::string& name) {
michael@0:   DCHECK(impl_);
michael@0: 
michael@0:   if (!impl_)
michael@0:     return 0;
michael@0: 
michael@0:   int counter_id = 0;
michael@0:   {
michael@0:     // To add a counter to the shared memory, we need the
michael@0:     // shared memory lock.
michael@0:     base::SharedMemoryAutoLock lock(impl_->shared_memory());
michael@0: 
michael@0:     // We have space, so create a new counter.
michael@0:     counter_id = FindCounterOrEmptyRow(name);
michael@0:     if (!counter_id)
michael@0:       return 0;
michael@0: 
michael@0:     std::string counter_name = name;
michael@0:     if (name.empty())
michael@0:       counter_name = kUnknownName;
michael@0:     base::strlcpy(impl_->counter_name(counter_id), counter_name.c_str(),
michael@0:                   kMaxCounterNameLength);
michael@0:   }
michael@0: 
michael@0:   // now add to our in-memory cache
michael@0:   {
michael@0:     AutoLock lock(counters_lock_);
michael@0:     counters_[name] = counter_id;
michael@0:   }
michael@0:   return counter_id;
michael@0: }
michael@0: 
michael@0: int* StatsTable::GetLocation(int counter_id, int slot_id) const {
michael@0:   if (!impl_)
michael@0:     return NULL;
michael@0:   if (slot_id > impl_->max_threads())
michael@0:     return NULL;
michael@0: 
michael@0:   int* row = impl_->row(counter_id);
michael@0:   return &(row[slot_id-1]);
michael@0: }
michael@0: 
michael@0: const char* StatsTable::GetRowName(int index) const {
michael@0:   if (!impl_)
michael@0:     return NULL;
michael@0: 
michael@0:   return impl_->counter_name(index);
michael@0: }
michael@0: 
michael@0: int StatsTable::GetRowValue(int index, int pid) const {
michael@0:   if (!impl_)
michael@0:     return 0;
michael@0: 
michael@0:   int rv = 0;
michael@0:   int* row = impl_->row(index);
michael@0:   for (int slot_id = 0; slot_id < impl_->max_threads(); slot_id++) {
michael@0:     if (pid == 0 || *impl_->thread_pid(slot_id) == pid)
michael@0:       rv += row[slot_id];
michael@0:   }
michael@0:   return rv;
michael@0: }
michael@0: 
michael@0: int StatsTable::GetRowValue(int index) const {
michael@0:   return GetRowValue(index, 0);
michael@0: }
michael@0: 
michael@0: int StatsTable::GetCounterValue(const std::string& name, int pid) {
michael@0:   if (!impl_)
michael@0:     return 0;
michael@0: 
michael@0:   int row = FindCounter(name);
michael@0:   if (!row)
michael@0:     return 0;
michael@0:   return GetRowValue(row, pid);
michael@0: }
michael@0: 
michael@0: int StatsTable::GetCounterValue(const std::string& name) {
michael@0:   return GetCounterValue(name, 0);
michael@0: }
michael@0: 
michael@0: int StatsTable::GetMaxCounters() const {
michael@0:   if (!impl_)
michael@0:     return 0;
michael@0:   return impl_->max_counters();
michael@0: }
michael@0: 
michael@0: int StatsTable::GetMaxThreads() const {
michael@0:   if (!impl_)
michael@0:     return 0;
michael@0:   return impl_->max_threads();
michael@0: }
michael@0: 
michael@0: int* StatsTable::FindLocation(const char* name) {
michael@0:   // Get the static StatsTable
michael@0:   StatsTable *table = StatsTable::current();
michael@0:   if (!table)
michael@0:     return NULL;
michael@0: 
michael@0:   // Get the slot for this thread.  Try to register
michael@0:   // it if none exists.
michael@0:   int slot = table->GetSlot();
michael@0:   if (!slot && !(slot = table->RegisterThread("")))
michael@0:       return NULL;
michael@0: 
michael@0:   // Find the counter id for the counter.
michael@0:   std::string str_name(name);
michael@0:   int counter = table->FindCounter(str_name);
michael@0: 
michael@0:   // Now we can find the location in the table.
michael@0:   return table->GetLocation(counter, slot);
michael@0: }