xpcom/base/nsMemoryImpl.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "nsMemory.h"
   8 #include "nsThreadUtils.h"
   9
  10 #include "nsIObserver.h"
  11 #include "nsIObserverService.h"
  12 #include "nsIRunnable.h"
  13 #include "nsISimpleEnumerator.h"
  14
  15 #include "nsCOMPtr.h"
  16 #include "mozilla/Services.h"
  17 #include "mozilla/Atomics.h"
  18 #include "mozilla/IntegerPrintfMacros.h"
  19
  20 #ifdef ANDROID
  21 #  include <stdio.h>
  22
  23 // Minimum memory threshold for a device to be considered
  24 // a low memory platform. This value has be in sync with
  25 // Java's equivalent threshold, defined in HardwareUtils.java
  26 #  define LOW_MEMORY_THRESHOLD_KB (384 * 1024)
  27 #endif
  28
  29 static mozilla::Atomic<bool> sIsFlushing;
  30 static PRIntervalTime sLastFlushTime = 0;
  31
  32 // static
  33 bool nsMemory::IsLowMemoryPlatform() {
  34 #ifdef ANDROID
  35   static int sLowMemory =
  36       -1;  // initialize to unknown, lazily evaluate to 0 or 1
  37   if (sLowMemory == -1) {
  38     sLowMemory = 0;  // assume "not low memory" in case file operations fail
  39
  40     // check if MemTotal from /proc/meminfo is less than LOW_MEMORY_THRESHOLD_KB
  41     FILE* fd = fopen("/proc/meminfo", "r");
  42     if (!fd) {
  43       return false;
  44     }
  45     uint64_t mem = 0;
  46     int rv = fscanf(fd, "MemTotal: %" PRIu64 " kB", &mem);
  47     if (fclose(fd)) {
  48       return false;
  49     }
  50     if (rv != 1) {
  51       return false;
  52     }
  53     sLowMemory = (mem < LOW_MEMORY_THRESHOLD_KB) ? 1 : 0;
  54   }
  55   return (sLowMemory == 1);
  56 #else
  57   return false;
  58 #endif
  59 }
  60
  61 static void RunFlushers(const char16_t* aReason) {
  62   nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
  63   if (os) {
  64     // Instead of:
  65     //  os->NotifyObservers(this, "memory-pressure", aReason);
  66     // we are going to do this manually to see who/what is
  67     // deallocating.
  68
  69     nsCOMPtr<nsISimpleEnumerator> e;
  70     os->EnumerateObservers("memory-pressure", getter_AddRefs(e));
  71
  72     if (e) {
  73       nsCOMPtr<nsIObserver> observer;
  74       bool loop = true;
  75
  76       while (NS_SUCCEEDED(e->HasMoreElements(&loop)) && loop) {
  77         nsCOMPtr<nsISupports> supports;
  78         e->GetNext(getter_AddRefs(supports));
  79
  80         if (!supports) {
  81           continue;
  82         }
  83
  84         observer = do_QueryInterface(supports);
  85         observer->Observe(observer, "memory-pressure", aReason);
  86       }
  87     }
  88   }
  89
  90   sIsFlushing = false;
  91 }
  92
  93 static nsresult FlushMemory(const char16_t* aReason, bool aImmediate) {
  94   if (aImmediate) {
  95     // They've asked us to run the flusher *immediately*. We've
  96     // got to be on the UI main thread for us to be able to do
  97     // that...are we?
  98     if (!NS_IsMainThread()) {
  99       NS_ERROR("can't synchronously flush memory: not on UI thread");
 100       return NS_ERROR_FAILURE;
 101     }
 102   }
 103
 104   bool lastVal = sIsFlushing.exchange(true);
 105   if (lastVal) {
 106     return NS_OK;
 107   }
 108
 109   PRIntervalTime now = PR_IntervalNow();
 110
 111   // Run the flushers immediately if we can; otherwise, proxy to the
 112   // UI thread and run 'em asynchronously.
 113   nsresult rv = NS_OK;
 114   if (aImmediate) {
 115     RunFlushers(aReason);
 116   } else {
 117     // Don't broadcast more than once every 1000ms to avoid being noisy
 118     if (PR_IntervalToMicroseconds(now - sLastFlushTime) > 1000) {
 119       nsCOMPtr<nsIRunnable> runnable(NS_NewRunnableFunction(
 120           "FlushMemory",
 121           [reason = aReason]() -> void { RunFlushers(reason); }));
 122       NS_DispatchToMainThread(runnable.forget());
 123     }
 124   }
 125
 126   sLastFlushTime = now;
 127   return rv;
 128 }
 129
 130 nsresult nsMemory::HeapMinimize(bool aImmediate) {
 131   return FlushMemory(u"heap-minimize", aImmediate);
 132 }