toolkit/xre/AutoSQLiteLifetime.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "nsDebug.h"
   7 #include "AutoSQLiteLifetime.h"
   8 #include "sqlite3.h"
   9
  10 #ifdef MOZ_MEMORY
  11 #  include "mozmemory.h"
  12 #  ifdef MOZ_DMD
  13 #    include "nsIMemoryReporter.h"
  14 #    include "DMD.h"
  15
  16 namespace mozilla {
  17 namespace storage {
  18 extern mozilla::Atomic<size_t> gSqliteMemoryUsed;
  19 }
  20 }  // namespace mozilla
  21
  22 using mozilla::storage::gSqliteMemoryUsed;
  23
  24 #  endif
  25
  26 namespace {
  27
  28 // By default, SQLite tracks the size of all its heap blocks by adding an extra
  29 // 8 bytes at the start of the block to hold the size.  Unfortunately, this
  30 // causes a lot of 2^N-sized allocations to be rounded up by jemalloc
  31 // allocator, wasting memory.  For example, a request for 1024 bytes has 8
  32 // bytes added, becoming a request for 1032 bytes, and jemalloc rounds this up
  33 // to 2048 bytes, wasting 1012 bytes.  (See bug 676189 for more details.)
  34 //
  35 // So we register jemalloc as the malloc implementation, which avoids this
  36 // 8-byte overhead, and thus a lot of waste.  This requires us to provide a
  37 // function, sqliteMemRoundup(), which computes the actual size that will be
  38 // allocated for a given request.  SQLite uses this function before all
  39 // allocations, and may be able to use any excess bytes caused by the rounding.
  40 //
  41 // Note: the wrappers for malloc, realloc and moz_malloc_usable_size are
  42 // necessary because the sqlite_mem_methods type signatures differ slightly
  43 // from the standard ones -- they use int instead of size_t.  But we don't need
  44 // a wrapper for free.
  45
  46 #  ifdef MOZ_DMD
  47
  48 // sqlite does its own memory accounting, and we use its numbers in our memory
  49 // reporters.  But we don't want sqlite's heap blocks to show up in DMD's
  50 // output as unreported, so we mark them as reported when they're allocated and
  51 // mark them as unreported when they are freed.
  52 //
  53 // In other words, we are marking all sqlite heap blocks as reported even
  54 // though we're not reporting them ourselves.  Instead we're trusting that
  55 // sqlite is fully and correctly accounting for all of its heap blocks via its
  56 // own memory accounting.  Well, we don't have to trust it entirely, because
  57 // it's easy to keep track (while doing this DMD-specific marking) of exactly
  58 // how much memory SQLite is using.  And we can compare that against what
  59 // SQLite reports it is using.
  60
  61 MOZ_DEFINE_MALLOC_SIZE_OF_ON_ALLOC(SqliteMallocSizeOfOnAlloc)
  62 MOZ_DEFINE_MALLOC_SIZE_OF_ON_FREE(SqliteMallocSizeOfOnFree)
  63
  64 #  endif
  65
  66 static void* sqliteMemMalloc(int n) {
  67   void* p = ::malloc(n);
  68 #  ifdef MOZ_DMD
  69   gSqliteMemoryUsed += SqliteMallocSizeOfOnAlloc(p);
  70 #  endif
  71   return p;
  72 }
  73
  74 static void sqliteMemFree(void* p) {
  75 #  ifdef MOZ_DMD
  76   gSqliteMemoryUsed -= SqliteMallocSizeOfOnFree(p);
  77 #  endif
  78   ::free(p);
  79 }
  80
  81 static void* sqliteMemRealloc(void* p, int n) {
  82 #  ifdef MOZ_DMD
  83   gSqliteMemoryUsed -= SqliteMallocSizeOfOnFree(p);
  84   void* pnew = ::realloc(p, n);
  85   if (pnew) {
  86     gSqliteMemoryUsed += SqliteMallocSizeOfOnAlloc(pnew);
  87   } else {
  88     // realloc failed;  undo the SqliteMallocSizeOfOnFree from above
  89     gSqliteMemoryUsed += SqliteMallocSizeOfOnAlloc(p);
  90   }
  91   return pnew;
  92 #  else
  93   return ::realloc(p, n);
  94 #  endif
  95 }
  96
  97 static int sqliteMemSize(void* p) { return ::moz_malloc_usable_size(p); }
  98
  99 static int sqliteMemRoundup(int n) {
 100   n = malloc_good_size(n);
 101
 102   // jemalloc can return blocks of size 2 and 4, but SQLite requires that all
 103   // allocations be 8-aligned.  So we round up sub-8 requests to 8.  This
 104   // wastes a small amount of memory but is obviously safe.
 105   return n <= 8 ? 8 : n;
 106 }
 107
 108 static int sqliteMemInit(void* p) { return 0; }
 109
 110 static void sqliteMemShutdown(void* p) {}
 111
 112 const sqlite3_mem_methods memMethods = {
 113     &sqliteMemMalloc,  &sqliteMemFree, &sqliteMemRealloc,  &sqliteMemSize,
 114     &sqliteMemRoundup, &sqliteMemInit, &sqliteMemShutdown, nullptr};
 115
 116 }  // namespace
 117
 118 #endif  // MOZ_MEMORY
 119
 120 namespace mozilla {
 121
 122 AutoSQLiteLifetime::AutoSQLiteLifetime() {
 123   if (++AutoSQLiteLifetime::sSingletonEnforcer != 1) {
 124     MOZ_CRASH("multiple instances of AutoSQLiteLifetime constructed!");
 125   }
 126
 127 #ifdef MOZ_MEMORY
 128   sResult = ::sqlite3_config(SQLITE_CONFIG_MALLOC, &memMethods);
 129 #else
 130   sResult = SQLITE_OK;
 131 #endif
 132
 133   if (sResult == SQLITE_OK) {
 134     // TODO (bug 1191405): do not preallocate the connections caches until we
 135     // have figured the impact on our consumers and memory.
 136     sqlite3_config(SQLITE_CONFIG_PAGECACHE, NULL, 0, 0);
 137
 138     // Explicitly initialize sqlite3.  Although this is implicitly called by
 139     // various sqlite3 functions (and the sqlite3_open calls in our case),
 140     // the documentation suggests calling this directly.  So we do.
 141     sResult = ::sqlite3_initialize();
 142   }
 143 }
 144
 145 AutoSQLiteLifetime::~AutoSQLiteLifetime() {
 146   // Shutdown the sqlite3 API.  Warn if shutdown did not turn out okay, but
 147   // there is nothing actionable we can do in that case.
 148   sResult = ::sqlite3_shutdown();
 149   NS_WARNING_ASSERTION(sResult == SQLITE_OK,
 150                        "sqlite3 did not shutdown cleanly.");
 151 }
 152
 153 int AutoSQLiteLifetime::sSingletonEnforcer = 0;
 154 int AutoSQLiteLifetime::sResult = SQLITE_MISUSE;
 155
 156 }  // namespace mozilla