5611f70b3d
This is a reland of bc33f5aeba
Contributed by titzer@chromium.org
Original change's description:
> [arraybuffer] Rearchitect backing store ownership
>
> This CL completely rearchitects the ownership of array buffer backing stores,
> consolidating ownership into a {BackingStore} C++ object that is tracked
> throughout V8 using unique_ptr and shared_ptr where appropriate.
>
> Overall, lifetime management is simpler and more explicit. The numerous
> ways that array buffers were initialized have been streamlined to one
> Attach() method on JSArrayBuffer. The array buffer tracker in the
> GC implementation now manages std::shared_ptr<BackingStore> pointers,
> and the construction and destruction of the BackingStore object itself
> handles the underlying page or embedder-allocated memory.
>
> The embedder API remains unchanged for now. We use the
> v8::ArrayBuffer::Contents struct to hide an additional shared_ptr to
> keep the backing store alive properly, even in the case of aliases
> from live heap objects. Thus the embedder has a lower chance of making
> a mistake. Long-term, we should move the embedder to a model where they
> manage backing stores using shared_ptr to an opaque backing store object.
TBR=yangguo@chromium.org
BUG=v8:9380,v8:9221,chromium:986318
Change-Id: If671a4a9ca0476e8f084efae46e0d2bf99ed99ef
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1731005
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63041}
38 lines
1.0 KiB
JavaScript
38 lines
1.0 KiB
JavaScript
// Copyright 2019 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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function AllocMemory(pages, max = pages) {
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let m =
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new WebAssembly.Memory({initial : pages, maximum : max, shared : true});
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let v = new Int32Array(m.buffer);
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return {memory : m, view : v};
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}
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function RunSomeAllocs(total, retained, pages, max = pages) {
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print(`-------iterations = ${total}, retained = ${retained} -------`);
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var array = new Array(retained);
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for (var i = 0; i < total; i++) {
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if ((i % 25) == 0)
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print(`iteration ${i}`);
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let pair = AllocMemory(pages, max);
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// For some iterations, retain the memory, view, or both.
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switch (i % 3) {
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case 0:
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pair.memory = null;
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break;
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case 1:
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pair.view = null;
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break;
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case 2:
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break;
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}
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array[i % retained] = pair;
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}
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}
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RunSomeAllocs(10, 1, 1, 1);
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RunSomeAllocs(100, 3, 1, 1);
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RunSomeAllocs(1000, 10, 1, 1);
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RunSomeAllocs(10000, 20, 1, 1);
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