gecko-dev/xpcom/threads/nsMemoryPressure.cpp

54 lines
1.6 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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 "nsMemoryPressure.h"
#include "mozilla/Assertions.h"
#include "mozilla/Atomics.h"
#include "nsThreadUtils.h"
using namespace mozilla;
static Atomic<int32_t, Relaxed> sMemoryPressurePending;
static_assert(MemPressure_None == 0,
"Bad static initialization with the default constructor.");
MemoryPressureState
NS_GetPendingMemoryPressure()
{
int32_t value = sMemoryPressurePending.exchange(MemPressure_None);
return MemoryPressureState(value);
}
void
NS_DispatchEventualMemoryPressure(MemoryPressureState state)
{
/*
* A new memory pressure event erases an ongoing memory pressure, but an
* existing "new" memory pressure event takes precedence over a new "ongoing"
* memory pressure event.
*/
switch (state) {
case MemPressure_None:
sMemoryPressurePending = MemPressure_None;
break;
case MemPressure_New:
sMemoryPressurePending = MemPressure_New;
break;
case MemPressure_Ongoing:
sMemoryPressurePending.compareExchange(MemPressure_None, MemPressure_Ongoing);
break;
}
}
nsresult
NS_DispatchMemoryPressure(MemoryPressureState state)
{
NS_DispatchEventualMemoryPressure(state);
nsCOMPtr<nsIRunnable> event = new nsRunnable;
return NS_DispatchToMainThread(event);
}