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67a43f4a6a
When memory-pressure events were first used in an e10s environment it was to implement memory minimization from about:memory. However when low memory detection was first introduced in Firefox OS an issue arised with this scheme: every process was using a kernel-based low-latency mechanism to detect low memory scenarios and send memory-pressure events; but the main process events were also being forwarded to all child processes causing listeners to be triggered twice. Because of this -no-forward events were introduced and used. Currently however low-memory is detected via polling, so there will always be a significant delay between the beginning of the low-memory scenario and its detection. Because of this there is no value in having content processes poll on their own and it's best to have only the main process do it and then forward the memory-pressure events to all child processes. MozReview-Commit-ID: AMQOsEgECme --HG-- extra : rebase_source : 1b408b31dd27940981407f50f2e5f07e354b16d7
64 lines
2.5 KiB
Plaintext
64 lines
2.5 KiB
Plaintext
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "nsISupports.idl"
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/**
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*
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* nsIMemory: interface to allocate and deallocate memory. Also provides
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* for notifications in low-memory situations.
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*
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* The frozen exported symbols moz_xmalloc, moz_xrealloc, and free
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* provide a more efficient way to access XPCOM memory allocation. Using
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* those symbols is preferred to using the methods on this interface.
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*
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* A client that wishes to be notified of low memory situations (for
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* example, because the client maintains a large memory cache that
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* could be released when memory is tight) should register with the
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* observer service (see nsIObserverService) using the topic
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* "memory-pressure". There are specific types of notications
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* that can occur. These types will be passed as the |aData|
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* parameter of the of the "memory-pressure" notification:
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*
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* "low-memory"
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* This will be passed as the extra data when the pressure
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* observer is being asked to flush for low-memory conditions.
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*
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* "low-memory-ongoing"
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* This will be passed when we continue to be in a low-memory
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* condition and we want to flush caches and do other cheap
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* forms of memory minimization, but heavy handed approaches like
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* a GC are unlikely to succeed.
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*
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* "heap-minimize"
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* This will be passed as the extra data when the pressure
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* observer is being asked to flush because of a heap minimize
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* call.
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*/
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[scriptable, uuid(1e004834-6d8f-425a-bc9c-a2812ed43bb7)]
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interface nsIMemory : nsISupports
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{
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/**
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* Attempts to shrink the heap.
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* @param immediate - if true, heap minimization will occur
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* immediately if the call was made on the main thread. If
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* false, the flush will be scheduled to happen when the app is
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* idle.
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* @throws NS_ERROR_FAILURE if 'immediate' is set an the call
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* was not on the application's main thread.
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*/
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void heapMinimize(in boolean immediate);
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/**
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* This predicate can be used to determine if the platform is a "low-memory"
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* platform. Callers may use this to dynamically tune their behaviour
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* to favour reduced memory usage at the expense of performance. The value
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* returned by this function will not change over the lifetime of the process.
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*/
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boolean isLowMemoryPlatform();
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};
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