lib/pool: only flush buffers if they are unused between flush intervals
This commit is contained in:
Nick Craig-Wood
parent
08c4854e00
commit
da90069462
167
lib/pool/pool.go
167
lib/pool/pool.go
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@ -5,21 +5,31 @@ package pool
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import (
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"fmt"
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"log"
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"sync/atomic"
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"sync"
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"time"
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"github.com/ncw/rclone/lib/mmap"
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)
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// Pool of internal buffers
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//
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// We hold buffers in cache. Every time we Get or Put we update
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// minFill which is the minimum len(cache) seen.
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//
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// Every flushTime we remove minFill buffers from the cache as they
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// were not used in the previous flushTime interval.
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type Pool struct {
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cache chan []byte
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bufferSize int
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timer *time.Timer
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inUse int32
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flushTime time.Duration
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alloc func(int) ([]byte, error)
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free func([]byte) error
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mu sync.Mutex
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cache [][]byte
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minFill int // the minimum fill of the cache
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bufferSize int
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poolSize int
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timer *time.Timer
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inUse int
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flushTime time.Duration
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flushPending bool
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alloc func(int) ([]byte, error)
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free func([]byte) error
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}
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// New makes a buffer pool
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@ -30,7 +40,8 @@ type Pool struct {
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// useMmap should be set to use mmap allocations
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func New(flushTime time.Duration, bufferSize, poolSize int, useMmap bool) *Pool {
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bp := &Pool{
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cache: make(chan []byte, poolSize),
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cache: make([][]byte, 0, poolSize),
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poolSize: poolSize,
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flushTime: flushTime,
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bufferSize: bufferSize,
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}
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@ -45,47 +56,113 @@ func New(flushTime time.Duration, bufferSize, poolSize int, useMmap bool) *Pool
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return nil
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}
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}
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bp.timer = time.AfterFunc(flushTime, bp.Flush)
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bp.timer = time.AfterFunc(flushTime, bp.flushAged)
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return bp
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}
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// get gets the last buffer in bp.cache
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//
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// Call with mu held
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func (bp *Pool) get() []byte {
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n := len(bp.cache) - 1
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buf := bp.cache[n]
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bp.cache[n] = nil // clear buffer pointer from bp.cache
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bp.cache = bp.cache[:n]
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return buf
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}
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// put puts the buffer on the end of bp.cache
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//
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// Call with mu held
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func (bp *Pool) put(buf []byte) {
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bp.cache = append(bp.cache, buf)
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}
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// flush n entries from the entire buffer pool
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// Call with mu held
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func (bp *Pool) flush(n int) {
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for i := 0; i < n; i++ {
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_ = bp.get()
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}
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bp.minFill = len(bp.cache)
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}
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// Flush the entire buffer pool
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func (bp *Pool) Flush() {
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for {
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select {
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case b := <-bp.cache:
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bp.freeBuffer(b)
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default:
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return
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}
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bp.mu.Lock()
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bp.flush(len(bp.cache))
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bp.mu.Unlock()
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}
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// Remove bp.minFill buffers
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func (bp *Pool) flushAged() {
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bp.mu.Lock()
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bp.flushPending = false
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bp.flush(bp.minFill)
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// If there are still items in the cache, schedule another flush
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if len(bp.cache) != 0 {
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bp.kickFlusher()
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}
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bp.mu.Unlock()
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}
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// InUse returns the approximate number of buffers in use which
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// haven't been returned to the pool.
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// InUse returns the number of buffers in use which haven't been
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// returned to the pool
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func (bp *Pool) InUse() int {
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return int(atomic.LoadInt32(&bp.inUse))
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bp.mu.Lock()
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defer bp.mu.Unlock()
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return bp.inUse
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}
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// starts or resets the buffer flusher timer
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// InPool returns the number of buffers in the pool
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func (bp *Pool) InPool() int {
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bp.mu.Lock()
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defer bp.mu.Unlock()
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return len(bp.cache)
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}
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// starts or resets the buffer flusher timer - call with mu held
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func (bp *Pool) kickFlusher() {
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if bp.flushPending {
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return
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}
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bp.flushPending = true
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bp.timer.Reset(bp.flushTime)
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}
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// Make sure minFill is correct - call with mu held
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func (bp *Pool) updateMinFill() {
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if len(bp.cache) < bp.minFill {
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bp.minFill = len(bp.cache)
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}
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}
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// Get a buffer from the pool or allocate one
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func (bp *Pool) Get() []byte {
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select {
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case b := <-bp.cache:
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return b
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default:
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bp.mu.Lock()
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var buf []byte
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waitTime := time.Millisecond
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for {
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if len(bp.cache) > 0 {
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buf = bp.get()
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break
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} else {
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var err error
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buf, err = bp.alloc(bp.bufferSize)
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if err == nil {
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break
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}
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log.Printf("Failed to get memory for buffer, waiting for %v: %v", waitTime, err)
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bp.mu.Unlock()
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time.Sleep(waitTime)
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bp.mu.Lock()
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waitTime *= 2
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}
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}
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mem, err := bp.alloc(bp.bufferSize)
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if err != nil {
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log.Printf("Failed to get memory for buffer, waiting for a freed one: %v", err)
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return <-bp.cache
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}
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atomic.AddInt32(&bp.inUse, 1)
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return mem
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bp.inUse++
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bp.updateMinFill()
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bp.mu.Unlock()
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return buf
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}
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// freeBuffer returns mem to the os if required
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@ -93,8 +170,6 @@ func (bp *Pool) freeBuffer(mem []byte) {
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err := bp.free(mem)
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if err != nil {
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log.Printf("Failed to free memory: %v", err)
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} else {
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atomic.AddInt32(&bp.inUse, -1)
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}
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}
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@ -102,17 +177,19 @@ func (bp *Pool) freeBuffer(mem []byte) {
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//
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// Note that if you try to return a buffer of the wrong size to Put it
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// will panic.
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func (bp *Pool) Put(mem []byte) {
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mem = mem[0:cap(mem)]
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if len(mem) != bp.bufferSize {
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panic(fmt.Sprintf("Returning buffer sized %d but expecting %d", len(mem), bp.bufferSize))
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func (bp *Pool) Put(buf []byte) {
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bp.mu.Lock()
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defer bp.mu.Unlock()
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buf = buf[0:cap(buf)]
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if len(buf) != bp.bufferSize {
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panic(fmt.Sprintf("Returning buffer sized %d but expecting %d", len(buf), bp.bufferSize))
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}
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select {
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case bp.cache <- mem:
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bp.kickFlusher()
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return
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default:
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if len(bp.cache) < bp.poolSize {
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bp.put(buf)
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} else {
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bp.freeBuffer(buf)
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}
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bp.freeBuffer(mem)
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mem = nil
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bp.inUse--
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bp.updateMinFill()
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bp.kickFlusher()
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}
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@ -1,53 +1,95 @@
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package pool
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import (
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"errors"
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"fmt"
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"math/rand"
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"testing"
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"time"
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"github.com/stretchr/testify/assert"
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)
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func testGetPut(t *testing.T, useMmap bool) {
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// makes the allocations be unreliable
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func makeUnreliable(bp *Pool) {
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bp.alloc = func(size int) ([]byte, error) {
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if rand.Intn(3) != 0 {
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return nil, errors.New("failed to allocate memory")
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}
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return make([]byte, size), nil
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}
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bp.free = func(b []byte) error {
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if rand.Intn(3) != 0 {
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return errors.New("failed to free memory")
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}
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return nil
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}
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}
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func testGetPut(t *testing.T, useMmap bool, unreliable bool) {
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bp := New(60*time.Second, 4096, 2, useMmap)
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if unreliable {
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makeUnreliable(bp)
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}
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assert.Equal(t, 0, bp.InUse())
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b1 := bp.Get()
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assert.Equal(t, 1, bp.InUse())
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assert.Equal(t, 0, bp.InPool())
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b2 := bp.Get()
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assert.Equal(t, 2, bp.InUse())
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assert.Equal(t, 0, bp.InPool())
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b3 := bp.Get()
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assert.Equal(t, 3, bp.InUse())
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assert.Equal(t, 0, bp.InPool())
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bp.Put(b1)
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assert.Equal(t, 3, bp.InUse())
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assert.Equal(t, 2, bp.InUse())
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assert.Equal(t, 1, bp.InPool())
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bp.Put(b2)
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assert.Equal(t, 3, bp.InUse())
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assert.Equal(t, 1, bp.InUse())
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assert.Equal(t, 2, bp.InPool())
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bp.Put(b3)
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assert.Equal(t, 2, bp.InUse())
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assert.Equal(t, 0, bp.InUse())
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assert.Equal(t, 2, bp.InPool())
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addr := func(b []byte) string {
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return fmt.Sprintf("%p", &b[0])
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}
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b1a := bp.Get()
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assert.Equal(t, b1, b1a)
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assert.Equal(t, 2, bp.InUse())
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assert.Equal(t, addr(b2), addr(b1a))
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assert.Equal(t, 1, bp.InUse())
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assert.Equal(t, 1, bp.InPool())
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b2a := bp.Get()
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assert.Equal(t, b1, b2a)
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assert.Equal(t, addr(b1), addr(b2a))
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assert.Equal(t, 2, bp.InUse())
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assert.Equal(t, 0, bp.InPool())
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bp.Put(b1a)
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bp.Put(b2a)
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assert.Equal(t, 2, bp.InUse())
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assert.Equal(t, 0, bp.InUse())
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assert.Equal(t, 2, bp.InPool())
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assert.Panics(t, func() {
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bp.Put(make([]byte, 1))
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})
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bp.Flush()
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assert.Equal(t, 0, bp.InUse())
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assert.Equal(t, 0, bp.InPool())
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}
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func testFlusher(t *testing.T, useMmap bool) {
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func testFlusher(t *testing.T, useMmap bool, unreliable bool) {
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bp := New(50*time.Millisecond, 4096, 2, useMmap)
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if unreliable {
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makeUnreliable(bp)
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}
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b1 := bp.Get()
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b2 := bp.Get()
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@ -55,38 +97,109 @@ func testFlusher(t *testing.T, useMmap bool) {
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bp.Put(b1)
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bp.Put(b2)
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bp.Put(b3)
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assert.Equal(t, 2, bp.InUse())
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assert.Equal(t, 0, bp.InUse())
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assert.Equal(t, 2, bp.InPool())
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bp.mu.Lock()
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assert.Equal(t, 0, bp.minFill)
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assert.Equal(t, true, bp.flushPending)
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bp.mu.Unlock()
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checkFlushHasHappened := func() {
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checkFlushHasHappened := func(desired int) {
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var n int
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for i := 0; i < 10; i++ {
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time.Sleep(100 * time.Millisecond)
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n = bp.InUse()
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if n == 0 {
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n = bp.InPool()
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if n <= desired {
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break
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}
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}
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assert.Equal(t, 0, n)
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assert.Equal(t, desired, n)
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}
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checkFlushHasHappened()
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checkFlushHasHappened(0)
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assert.Equal(t, 0, bp.InUse())
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assert.Equal(t, 0, bp.InPool())
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bp.mu.Lock()
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assert.Equal(t, 0, bp.minFill)
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assert.Equal(t, false, bp.flushPending)
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bp.mu.Unlock()
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// Now do manual aging to check it is working properly
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bp = New(100*time.Second, 4096, 2, useMmap)
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// Check the new one doesn't get flushed
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b1 = bp.Get()
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b2 = bp.Get()
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bp.Put(b1)
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assert.Equal(t, 1, bp.InUse())
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bp.Put(b2)
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checkFlushHasHappened()
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bp.mu.Lock()
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assert.Equal(t, 0, bp.minFill)
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assert.Equal(t, true, bp.flushPending)
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bp.mu.Unlock()
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bp.flushAged()
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assert.Equal(t, 0, bp.InUse())
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assert.Equal(t, 2, bp.InPool())
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bp.mu.Lock()
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assert.Equal(t, 2, bp.minFill)
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assert.Equal(t, true, bp.flushPending)
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bp.mu.Unlock()
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bp.Put(bp.Get())
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assert.Equal(t, 0, bp.InUse())
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assert.Equal(t, 2, bp.InPool())
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bp.mu.Lock()
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assert.Equal(t, 1, bp.minFill)
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assert.Equal(t, true, bp.flushPending)
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bp.mu.Unlock()
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bp.flushAged()
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assert.Equal(t, 0, bp.InUse())
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assert.Equal(t, 1, bp.InPool())
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bp.mu.Lock()
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assert.Equal(t, 1, bp.minFill)
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assert.Equal(t, true, bp.flushPending)
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bp.mu.Unlock()
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bp.flushAged()
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assert.Equal(t, 0, bp.InUse())
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assert.Equal(t, 0, bp.InPool())
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bp.mu.Lock()
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assert.Equal(t, 0, bp.minFill)
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assert.Equal(t, false, bp.flushPending)
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bp.mu.Unlock()
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}
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func TestPool(t *testing.T) {
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for _, useMmap := range []bool{false, true} {
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name := "make"
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if useMmap {
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name = "mmap"
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}
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t.Run(name, func(t *testing.T) {
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t.Run("GetPut", func(t *testing.T) { testGetPut(t, useMmap) })
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t.Run("Flusher", func(t *testing.T) { testFlusher(t, useMmap) })
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for _, test := range []struct {
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name string
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useMmap bool
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unreliable bool
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}{
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{
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name: "make",
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useMmap: false,
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unreliable: false,
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},
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{
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name: "mmap",
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useMmap: true,
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unreliable: false,
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},
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{
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name: "canFail",
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useMmap: false,
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unreliable: true,
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},
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} {
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t.Run(test.name, func(t *testing.T) {
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t.Run("GetPut", func(t *testing.T) { testGetPut(t, test.useMmap, test.unreliable) })
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t.Run("Flusher", func(t *testing.T) { testFlusher(t, test.useMmap, test.unreliable) })
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})
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}
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}
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