github.com/m3db/m3@v1.5.0/src/dbnode/storage/mem_tracker.go (about)

     1  // Copyright (c) 2019 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package storage
    22  
    23  import (
    24  	"sync"
    25  )
    26  
    27  type memoryTracker struct {
    28  	sync.Mutex
    29  
    30  	opts MemoryTrackerOptions
    31  
    32  	numLoadedBytes        int64
    33  	numPendingLoadedBytes int64
    34  
    35  	waitForDecWg *sync.WaitGroup
    36  }
    37  
    38  func (m *memoryTracker) IncNumLoadedBytes(x int64) (okToLoad bool) {
    39  	m.Lock()
    40  	defer m.Unlock()
    41  	limit := m.opts.numLoadedBytesLimit
    42  	if limit == 0 {
    43  		// Limit of 0 means no limit.
    44  		return true
    45  	}
    46  	// This check is optimistic in the sense that as long as the number of loaded bytes
    47  	// is currently under the limit then x is accepted, regardless of how far over the
    48  	// limit it brings the value of numLoadedBytes.
    49  	//
    50  	// The reason for this is to avoid scenarios where some process gets permanently
    51  	// stuck because the amount of data it needs to load at once is larger than the limit
    52  	// and as a result it's never able to make any progress.
    53  	//
    54  	// In practice this implementation should be fine for the vast majority of configurations
    55  	// and workloads.
    56  	if m.numLoadedBytes < limit {
    57  		m.numLoadedBytes += x
    58  		return true
    59  	}
    60  
    61  	return false
    62  }
    63  
    64  func (m *memoryTracker) NumLoadedBytes() int64 {
    65  	m.Lock()
    66  	defer m.Unlock()
    67  	return m.numLoadedBytes
    68  }
    69  
    70  func (m *memoryTracker) MarkLoadedAsPending() {
    71  	m.Lock()
    72  	m.numPendingLoadedBytes = m.numLoadedBytes
    73  	m.Unlock()
    74  }
    75  
    76  func (m *memoryTracker) DecPendingLoadedBytes() {
    77  	m.Lock()
    78  	m.numLoadedBytes -= m.numPendingLoadedBytes
    79  	m.numPendingLoadedBytes = 0
    80  	if m.waitForDecWg != nil {
    81  		m.waitForDecWg.Done()
    82  		m.waitForDecWg = nil
    83  	}
    84  	m.Unlock()
    85  }
    86  
    87  func (m *memoryTracker) WaitForDec() {
    88  	m.Lock()
    89  	if m.waitForDecWg == nil {
    90  		m.waitForDecWg = &sync.WaitGroup{}
    91  		m.waitForDecWg.Add(1)
    92  	}
    93  	wg := m.waitForDecWg
    94  	m.Unlock()
    95  	wg.Wait()
    96  }
    97  
    98  // MemoryTrackerOptions are the options for the MemoryTracker.
    99  type MemoryTrackerOptions struct {
   100  	numLoadedBytesLimit int64
   101  }
   102  
   103  // NewMemoryTrackerOptions creates a new MemoryTrackerOptions.
   104  func NewMemoryTrackerOptions(numLoadedBytesLimit int64) MemoryTrackerOptions {
   105  	return MemoryTrackerOptions{
   106  		numLoadedBytesLimit: numLoadedBytesLimit,
   107  	}
   108  }
   109  
   110  // NewMemoryTracker creates a new MemoryTracker.
   111  func NewMemoryTracker(opts MemoryTrackerOptions) MemoryTracker {
   112  	return &memoryTracker{
   113  		opts: opts,
   114  	}
   115  }