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075ad87a40
Also, do this for the initial slab for the task's allocator itself. This avoids memory allocations for async-lets. In case the async-task's memory demand does not exceed the initial slab size, it is now completely malloc-free. The refcount bits of an async-let task are initialized to "immortal" so that ARC operations don't have an effect on the task.
90 lines
2.8 KiB
C++
90 lines
2.8 KiB
C++
//===--- TaskAlloc.cpp - Task-local stack allocator -----------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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//
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// A task-local allocator that obeys a stack discipline.
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//
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// Because allocation is task-local, and there's at most one thread
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// running a task at once, no synchronization is required.
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//
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//===----------------------------------------------------------------------===//
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#include "swift/Runtime/Concurrency.h"
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#include "swift/ABI/Task.h"
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#include "TaskPrivate.h"
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#include "../runtime/StackAllocator.h"
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#include <stdlib.h>
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using namespace swift;
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namespace {
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/// The size of an allocator slab.
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///
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/// TODO: find the optimal value by experiment.
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static constexpr size_t SlabCapacity = 1024;
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using TaskAllocator = StackAllocator<SlabCapacity>;
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struct GlobalAllocator {
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TaskAllocator allocator;
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void *spaceForFirstSlab[64];
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GlobalAllocator() : allocator(spaceForFirstSlab, sizeof(spaceForFirstSlab)) {}
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};
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static_assert(alignof(TaskAllocator) <= alignof(decltype(AsyncTask::AllocatorPrivate)),
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"task allocator must not be more aligned than "
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"allocator-private slot");
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} // end anonymous namespace
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void swift::_swift_task_alloc_initialize(AsyncTask *task) {
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new (task->AllocatorPrivate) TaskAllocator();
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}
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void swift::_swift_task_alloc_initialize_with_slab(AsyncTask *task,
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void *firstSlabBuffer,
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size_t bufferCapacity) {
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new (task->AllocatorPrivate) TaskAllocator(firstSlabBuffer, bufferCapacity);
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}
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static TaskAllocator &allocator(AsyncTask *task) {
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if (task)
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return reinterpret_cast<TaskAllocator &>(task->AllocatorPrivate);
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// FIXME: this fall-back shouldn't be necessary, but it's useful
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// for now, since the current execution tests aren't setting up a task
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// properly.
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static GlobalAllocator global;
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return global.allocator;
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}
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void swift::_swift_task_alloc_destroy(AsyncTask *task) {
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allocator(task).~TaskAllocator();
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}
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void *swift::swift_task_alloc(size_t size) {
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return allocator(swift_task_getCurrent()).alloc(size);
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}
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void *swift::_swift_task_alloc_specific(AsyncTask *task, size_t size) {
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return allocator(task).alloc(size);
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}
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void swift::swift_task_dealloc(void *ptr) {
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allocator(swift_task_getCurrent()).dealloc(ptr);
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}
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void swift::_swift_task_dealloc_specific(AsyncTask *task, void *ptr) {
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allocator(task).dealloc(ptr);
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}
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