mirror of https://github.com/facebook/rocksdb.git
78 lines
3.1 KiB
C++
78 lines
3.1 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#pragma once
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#include "rocksdb/status.h"
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#include <memory>
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namespace ROCKSDB_NAMESPACE {
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// MemoryAllocator is an interface that a client can implement to supply custom
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// memory allocation and deallocation methods. See rocksdb/cache.h for more
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// information.
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// All methods should be thread-safe.
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class MemoryAllocator {
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public:
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virtual ~MemoryAllocator() = default;
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// Name of the cache allocator, printed in the log
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virtual const char* Name() const = 0;
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// Allocate a block of at least size. Has to be thread-safe.
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virtual void* Allocate(size_t size) = 0;
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// Deallocate previously allocated block. Has to be thread-safe.
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virtual void Deallocate(void* p) = 0;
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// Returns the memory size of the block allocated at p. The default
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// implementation that just returns the original allocation_size is fine.
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virtual size_t UsableSize(void* /*p*/, size_t allocation_size) const {
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// default implementation just returns the allocation size
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return allocation_size;
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}
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};
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struct JemallocAllocatorOptions {
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// Jemalloc tcache cache allocations by size class. For each size class,
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// it caches between 20 (for large size classes) to 200 (for small size
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// classes). To reduce tcache memory usage in case the allocator is access
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// by large number of threads, we can control whether to cache an allocation
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// by its size.
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bool limit_tcache_size = false;
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// Lower bound of allocation size to use tcache, if limit_tcache_size=true.
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// When used with block cache, it is recommneded to set it to block_size/4.
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size_t tcache_size_lower_bound = 1024;
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// Upper bound of allocation size to use tcache, if limit_tcache_size=true.
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// When used with block cache, it is recommneded to set it to block_size.
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size_t tcache_size_upper_bound = 16 * 1024;
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};
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// Generate memory allocators which allocates through Jemalloc and utilize
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// MADV_DONTDUMP through madvice to exclude cache items from core dump.
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// Applications can use the allocator with block cache to exclude block cache
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// usage from core dump.
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//
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// Implementation details:
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// The JemallocNodumpAllocator creates a delicated jemalloc arena, and all
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// allocations of the JemallocNodumpAllocator is through the same arena.
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// The memory allocator hooks memory allocation of the arena, and call
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// madvice() with MADV_DONTDUMP flag to exclude the piece of memory from
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// core dump. Side benefit of using single arena would be reduce of jemalloc
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// metadata for some workload.
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//
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// To mitigate mutex contention for using one single arena, jemalloc tcache
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// (thread-local cache) is enabled to cache unused allocations for future use.
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// The tcache normally incur 0.5M extra memory usage per-thread. The usage
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// can be reduce by limitting allocation sizes to cache.
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extern Status NewJemallocNodumpAllocator(
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JemallocAllocatorOptions& options,
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std::shared_ptr<MemoryAllocator>* memory_allocator);
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} // namespace ROCKSDB_NAMESPACE
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