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Revision df38c1ce660628f05b4686eeaf0b548295ce7967 authored by Mike Kolupaev on 22 April 2019, 15:17:45 UTC, committed by Facebook Github Bot on 22 April 2019, 15:20:35 UTC 
Add BlockBasedTableOptions::index_shortening (#5174)
 
Summary:
Introduce BlockBasedTableOptions::index_shortening to give users control on which key shortening techniques to be used in building index blocks. Before this patch, both separators and successor keys where shortened in indexes. With this patch, the default is set to kShortenSeparators to only shorten the separators. Since each index block has many separators and only one successor (last key), the change should not have negative impact on index block size. However it should prevent many unnecessary block loads where due to approximation introduced by shorted successor, seek would land us to the previous block and then fix it by moving to the next one.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5174

Differential Revision: D14884185

Pulled By: al13n321

fbshipit-source-id: 1b08bc8c03edcf09b6b8c16e9a7eea08ad4dd534
1 parent de76909
Raw File
concurrent_task_limiter_impl.cc 
//  Copyright (c) 2011-present, Facebook, Inc.  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).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.

#include "util/concurrent_task_limiter_impl.h"
#include "rocksdb/concurrent_task_limiter.h"

namespace rocksdb {

ConcurrentTaskLimiterImpl::ConcurrentTaskLimiterImpl(
    const std::string& name, int32_t max_outstanding_task)
    : name_(name),
      max_outstanding_tasks_{max_outstanding_task},
      outstanding_tasks_{0} {

}

ConcurrentTaskLimiterImpl::~ConcurrentTaskLimiterImpl() {
  assert(outstanding_tasks_ == 0);
}

const std::string& ConcurrentTaskLimiterImpl::GetName() const {
  return name_;
}

void ConcurrentTaskLimiterImpl::SetMaxOutstandingTask(int32_t limit) {
  max_outstanding_tasks_.store(limit, std::memory_order_relaxed);
}

void ConcurrentTaskLimiterImpl::ResetMaxOutstandingTask() {
  max_outstanding_tasks_.store(-1, std::memory_order_relaxed);
}

int32_t ConcurrentTaskLimiterImpl::GetOutstandingTask() const {
  return outstanding_tasks_.load(std::memory_order_relaxed);
}

std::unique_ptr<TaskLimiterToken> ConcurrentTaskLimiterImpl::GetToken(
    bool force) {
  int32_t limit = max_outstanding_tasks_.load(std::memory_order_relaxed);
  int32_t tasks = outstanding_tasks_.load(std::memory_order_relaxed);
  // force = true, bypass the throttle.
  // limit < 0 means unlimited tasks.
  while (force || limit < 0 || tasks < limit) {
    if (outstanding_tasks_.compare_exchange_weak(tasks, tasks + 1)) {
      return std::unique_ptr<TaskLimiterToken>(new TaskLimiterToken(this));
    }
  }
  return nullptr;
}

ConcurrentTaskLimiter* NewConcurrentTaskLimiter(
    const std::string& name, int32_t limit) {
  return new ConcurrentTaskLimiterImpl(name, limit);
}

TaskLimiterToken::~TaskLimiterToken() {
  --limiter_->outstanding_tasks_;
  assert(limiter_->outstanding_tasks_ >= 0);
}

}  // namespace rocksdb
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