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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
commit | e6918187568dbd01842d8d1d2c808ce16a894239 (patch) | |
tree | 64f88b554b444a49f656b6c656111a145cbbaa28 /src/rocksdb/cache/cache_entry_roles.h | |
parent | Initial commit. (diff) | |
download | ceph-e6918187568dbd01842d8d1d2c808ce16a894239.tar.xz ceph-e6918187568dbd01842d8d1d2c808ce16a894239.zip |
Adding upstream version 18.2.2.upstream/18.2.2
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/rocksdb/cache/cache_entry_roles.h')
-rw-r--r-- | src/rocksdb/cache/cache_entry_roles.h | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/src/rocksdb/cache/cache_entry_roles.h b/src/rocksdb/cache/cache_entry_roles.h new file mode 100644 index 000000000..5a49fdfd4 --- /dev/null +++ b/src/rocksdb/cache/cache_entry_roles.h @@ -0,0 +1,103 @@ +// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved. +// This source code is licensed under both the GPLv2 (found in the +// COPYING file in the root directory) and Apache 2.0 License +// (found in the LICENSE.Apache file in the root directory). + +#pragma once + +#include <array> +#include <cstdint> +#include <memory> +#include <type_traits> + +#include "rocksdb/cache.h" +#include "util/hash_containers.h" + +namespace ROCKSDB_NAMESPACE { + +extern std::array<std::string, kNumCacheEntryRoles> + kCacheEntryRoleToCamelString; +extern std::array<std::string, kNumCacheEntryRoles> + kCacheEntryRoleToHyphenString; + +// To associate cache entries with their role, we use a hack on the +// existing Cache interface. Because the deleter of an entry can authenticate +// the code origin of an entry, we can elaborate the choice of deleter to +// also encode role information, without inferring false role information +// from entries not choosing to encode a role. +// +// The rest of this file is for handling mappings between deleters and +// roles. + +// To infer a role from a deleter, the deleter must be registered. This +// can be done "manually" with this function. This function is thread-safe, +// and the registration mappings go into private but static storage. (Note +// that DeleterFn is a function pointer, not std::function. Registrations +// should not be too many.) +void RegisterCacheDeleterRole(Cache::DeleterFn fn, CacheEntryRole role); + +// Gets a copy of the registered deleter -> role mappings. This is the only +// function for reading the mappings made with RegisterCacheDeleterRole. +// Why only this interface for reading? +// * This function has to be thread safe, which could incur substantial +// overhead. We should not pay this overhead for every deleter look-up. +// * This is suitable for preparing for batch operations, like with +// CacheEntryStatsCollector. +// * The number of mappings should be sufficiently small (dozens). +UnorderedMap<Cache::DeleterFn, CacheEntryRole> CopyCacheDeleterRoleMap(); + +// ************************************************************** // +// An automatic registration infrastructure. This enables code +// to simply ask for a deleter associated with a particular type +// and role, and registration is automatic. In a sense, this is +// a small dependency injection infrastructure, because linking +// in new deleter instantiations is essentially sufficient for +// making stats collection (using CopyCacheDeleterRoleMap) aware +// of them. + +namespace cache_entry_roles_detail { + +template <typename T, CacheEntryRole R> +struct RegisteredDeleter { + RegisteredDeleter() { RegisterCacheDeleterRole(Delete, R); } + + // These have global linkage to help ensure compiler optimizations do not + // break uniqueness for each <T,R> + static void Delete(const Slice& /* key */, void* value) { + // Supports T == Something[], unlike delete operator + std::default_delete<T>()( + static_cast<typename std::remove_extent<T>::type*>(value)); + } +}; + +template <CacheEntryRole R> +struct RegisteredNoopDeleter { + RegisteredNoopDeleter() { RegisterCacheDeleterRole(Delete, R); } + + static void Delete(const Slice& /* key */, void* /* value */) { + // Here was `assert(value == nullptr);` but we can also put pointers + // to static data in Cache, for testing at least. + } +}; + +} // namespace cache_entry_roles_detail + +// Get an automatically registered deleter for value type T and role R. +// Based on C++ semantics, registration is invoked exactly once in a +// thread-safe way on first call to this function, for each <T, R>. +template <typename T, CacheEntryRole R> +Cache::DeleterFn GetCacheEntryDeleterForRole() { + static cache_entry_roles_detail::RegisteredDeleter<T, R> reg; + return reg.Delete; +} + +// Get an automatically registered no-op deleter (value should be nullptr) +// and associated with role R. This is used for Cache "reservation" entries +// such as for WriteBufferManager. +template <CacheEntryRole R> +Cache::DeleterFn GetNoopDeleterForRole() { + static cache_entry_roles_detail::RegisteredNoopDeleter<R> reg; + return reg.Delete; +} + +} // namespace ROCKSDB_NAMESPACE |