mirror of
https://github.com/facebook/rocksdb.git
synced 2024-11-25 22:44:05 +00:00
b81b430987
Summary: Using a TLS random instance for skiplist makes it smaller (useful for hash_skiplist_rep) and prepares skiplist for concurrent adds. This diff also modifies the branching factor math to avoid an unnecessary division. This diff has the effect of changing the sequence of skip list node height choices made by tests, so it has the potential to cause unit test failures for tests that implicitly rely on the exact structure of the skip list. Tests that try to exactly trigger a compaction are likely suspects for this problem (these tests have always been brittle to changes in the skiplist details). I've minimizes this risk by reseeding the main thread's Random at the beginning of each test, increasing the universal compaction size_ratio limit from 101% to 105% for some tests, and verifying that the tests pass many times. Test Plan: for i in `seq 0 9`; do make check; done Reviewers: sdong, igor Reviewed By: igor Subscribers: dhruba Differential Revision: https://reviews.facebook.net/D50439
40 lines
1,006 B
C++
40 lines
1,006 B
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
|
|
// This source code is licensed under the BSD-style license found in the
|
|
// LICENSE file in the root directory of this source tree. An additional grant
|
|
// of patent rights can be found in the PATENTS file in the same directory.
|
|
//
|
|
|
|
#include "util/random.h"
|
|
|
|
#include <pthread.h>
|
|
#include <stdint.h>
|
|
#include <string.h>
|
|
|
|
#include "port/likely.h"
|
|
#include "util/thread_local.h"
|
|
|
|
#if ROCKSDB_SUPPORT_THREAD_LOCAL
|
|
#define STORAGE_DECL static __thread
|
|
#else
|
|
#define STORAGE_DECL static
|
|
#endif
|
|
|
|
namespace rocksdb {
|
|
|
|
Random* Random::GetTLSInstance() {
|
|
STORAGE_DECL Random* tls_instance;
|
|
STORAGE_DECL std::aligned_storage<sizeof(Random)>::type tls_instance_bytes;
|
|
|
|
auto rv = tls_instance;
|
|
if (UNLIKELY(rv == nullptr)) {
|
|
const pthread_t self = pthread_self();
|
|
uint32_t seed = 0;
|
|
memcpy(&seed, &self, sizeof(seed));
|
|
rv = new (&tls_instance_bytes) Random(seed);
|
|
tls_instance = rv;
|
|
}
|
|
return rv;
|
|
}
|
|
|
|
} // namespace rocksdb
|