• Péter Szilágyi's avatar
    Godeps, vendor: convert dependency management to trash (#3198) · 289b3071
    Péter Szilágyi authored
    This commit converts the dependency management from Godeps to the vendor
    folder, also switching the tool from godep to trash. Since the upstream tool
    lacks a few features proposed via a few PRs, until those PRs are merged in
    (if), use github.com/karalabe/trash.
    
    You can update dependencies via trash --update.
    
    All dependencies have been updated to their latest version.
    
    Parts of the build system are reworked to drop old notions of Godeps and
    invocation of the go vet command so that it doesn't run against the vendor
    folder, as that will just blow up during vetting.
    
    The conversion drops OpenCL (and hence GPU mining support) from ethash and our
    codebase. The short reasoning is that there's noone to maintain and having
    opencl libs in our deps messes up builds as go install ./... tries to build
    them, failing with unsatisfied link errors for the C OpenCL deps.
    
    golang.org/x/net/context is not vendored in. We expect it to be fetched by the
    user (i.e. using go get). To keep ci.go builds reproducible the package is
    "vendored" in build/_vendor.
    289b3071
2q.go 4.91 KB
package lru

import (
	"fmt"
	"sync"

	"github.com/hashicorp/golang-lru/simplelru"
)

const (
	// Default2QRecentRatio is the ratio of the 2Q cache dedicated
	// to recently added entries that have only been accessed once.
	Default2QRecentRatio = 0.25

	// Default2QGhostEntries is the default ratio of ghost
	// entries kept to track entries recently evicted
	Default2QGhostEntries = 0.50
)

// TwoQueueCache is a thread-safe fixed size 2Q cache.
// 2Q is an enhancement over the standard LRU cache
// in that it tracks both frequently and recently used
// entries separately. This avoids a burst in access to new
// entries from evicting frequently used entries. It adds some
// additional tracking overhead to the standard LRU cache, and is
// computationally about 2x the cost, and adds some metadata over
// head. The ARCCache is similar, but does not require setting any
// parameters.
type TwoQueueCache struct {
	size       int
	recentSize int

	recent      *simplelru.LRU
	frequent    *simplelru.LRU
	recentEvict *simplelru.LRU
	lock        sync.RWMutex
}

// New2Q creates a new TwoQueueCache using the default
// values for the parameters.
func New2Q(size int) (*TwoQueueCache, error) {
	return New2QParams(size, Default2QRecentRatio, Default2QGhostEntries)
}

// New2QParams creates a new TwoQueueCache using the provided
// parameter values.
func New2QParams(size int, recentRatio float64, ghostRatio float64) (*TwoQueueCache, error) {
	if size <= 0 {
		return nil, fmt.Errorf("invalid size")
	}
	if recentRatio < 0.0 || recentRatio > 1.0 {
		return nil, fmt.Errorf("invalid recent ratio")
	}
	if ghostRatio < 0.0 || ghostRatio > 1.0 {
		return nil, fmt.Errorf("invalid ghost ratio")
	}

	// Determine the sub-sizes
	recentSize := int(float64(size) * recentRatio)
	evictSize := int(float64(size) * ghostRatio)

	// Allocate the LRUs
	recent, err := simplelru.NewLRU(size, nil)
	if err != nil {
		return nil, err
	}
	frequent, err := simplelru.NewLRU(size, nil)
	if err != nil {
		return nil, err
	}
	recentEvict, err := simplelru.NewLRU(evictSize, nil)
	if err != nil {
		return nil, err
	}

	// Initialize the cache
	c := &TwoQueueCache{
		size:        size,
		recentSize:  recentSize,
		recent:      recent,
		frequent:    frequent,
		recentEvict: recentEvict,
	}
	return c, nil
}

func (c *TwoQueueCache) Get(key interface{}) (interface{}, bool) {
	c.lock.Lock()
	defer c.lock.Unlock()

	// Check if this is a frequent value
	if val, ok := c.frequent.Get(key); ok {
		return val, ok
	}

	// If the value is contained in recent, then we
	// promote it to frequent
	if val, ok := c.recent.Peek(key); ok {
		c.recent.Remove(key)
		c.frequent.Add(key, val)
		return val, ok
	}

	// No hit
	return nil, false
}

func (c *TwoQueueCache) Add(key, value interface{}) {
	c.lock.Lock()
	defer c.lock.Unlock()

	// Check if the value is frequently used already,
	// and just update the value
	if c.frequent.Contains(key) {
		c.frequent.Add(key, value)
		return
	}

	// Check if the value is recently used, and promote
	// the value into the frequent list
	if c.recent.Contains(key) {
		c.recent.Remove(key)
		c.frequent.Add(key, value)
		return
	}

	// If the value was recently evicted, add it to the
	// frequently used list
	if c.recentEvict.Contains(key) {
		c.ensureSpace(true)
		c.recentEvict.Remove(key)
		c.frequent.Add(key, value)
		return
	}

	// Add to the recently seen list
	c.ensureSpace(false)
	c.recent.Add(key, value)
	return
}

// ensureSpace is used to ensure we have space in the cache
func (c *TwoQueueCache) ensureSpace(recentEvict bool) {
	// If we have space, nothing to do
	recentLen := c.recent.Len()
	freqLen := c.frequent.Len()
	if recentLen+freqLen < c.size {
		return
	}

	// If the recent buffer is larger than
	// the target, evict from there
	if recentLen > 0 && (recentLen > c.recentSize || (recentLen == c.recentSize && !recentEvict)) {
		k, _, _ := c.recent.RemoveOldest()
		c.recentEvict.Add(k, nil)
		return
	}

	// Remove from the frequent list otherwise
	c.frequent.RemoveOldest()
}

func (c *TwoQueueCache) Len() int {
	c.lock.RLock()
	defer c.lock.RUnlock()
	return c.recent.Len() + c.frequent.Len()
}

func (c *TwoQueueCache) Keys() []interface{} {
	c.lock.RLock()
	defer c.lock.RUnlock()
	k1 := c.frequent.Keys()
	k2 := c.recent.Keys()
	return append(k1, k2...)
}

func (c *TwoQueueCache) Remove(key interface{}) {
	c.lock.Lock()
	defer c.lock.Unlock()
	if c.frequent.Remove(key) {
		return
	}
	if c.recent.Remove(key) {
		return
	}
	if c.recentEvict.Remove(key) {
		return
	}
}

func (c *TwoQueueCache) Purge() {
	c.lock.Lock()
	defer c.lock.Unlock()
	c.recent.Purge()
	c.frequent.Purge()
	c.recentEvict.Purge()
}

func (c *TwoQueueCache) Contains(key interface{}) bool {
	c.lock.RLock()
	defer c.lock.RUnlock()
	return c.frequent.Contains(key) || c.recent.Contains(key)
}

func (c *TwoQueueCache) Peek(key interface{}) (interface{}, bool) {
	c.lock.RLock()
	defer c.lock.RUnlock()
	if val, ok := c.frequent.Peek(key); ok {
		return val, ok
	}
	return c.recent.Peek(key)
}