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Code Issues Releases Wiki Activity

Check cap instead of len in bloblru

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restic dump uses bloblru.Cache to keep buffers alive, but also reuses
evicted buffers. That means large buffers may be used to store small
blobs, causing the cache to think it's using less memory than it
actually does.
This commit is contained in:
greatroar 2021-10-03 09:33:58 +02:00
parent 1ebcb1d097
commit 634a9c162d
2 changed files with 9 additions and 7 deletions
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8
internal/bloblru/cache.go
View file

@ -47,7 +47,7 @@ func New(size int) *Cache {
func (c *Cache) Add(id restic.ID, blob []byte) (old []byte) {
debug.Log("bloblru.Cache: add %v", id)
size := len(blob) + overhead
size := cap(blob) + overhead
if size > c.size {
return
}
@ -66,7 +66,7 @@ func (c *Cache) Add(id restic.ID, blob []byte) (old []byte) {
for size > c.free {
_, val, _ := c.c.RemoveOldest()
b := val.([]byte)
if len(b) > len(old) {
if cap(b) > cap(old) {
// We can only return one buffer, so pick the largest.
old = b
}
@ -91,6 +91,6 @@ func (c *Cache) Get(id restic.ID) ([]byte, bool) {
func (c *Cache) evict(key, value interface{}) {
blob := value.([]byte)
debug.Log("bloblru.Cache: evict %v, %d bytes", key, len(blob))
c.free += len(blob) + overhead
debug.Log("bloblru.Cache: evict %v, %d bytes", key, cap(blob))
c.free += cap(blob) + overhead
}

8
internal/bloblru/cache_test.go
View file

@ -28,9 +28,11 @@ func TestCache(t *testing.T) {
rtest.Equals(t, exp, blob)
}
addAndCheck(id1, make([]byte, 32*kiB))
addAndCheck(id2, make([]byte, 30*kiB))
addAndCheck(id3, make([]byte, 10*kiB))
// Our blobs have len 1 but larger cap. The cache should check the cap,
// since it more reliably indicates the amount of memory kept alive.
addAndCheck(id1, make([]byte, 1, 32*kiB))
addAndCheck(id2, make([]byte, 1, 30*kiB))
addAndCheck(id3, make([]byte, 1, 10*kiB))
_, ok := c.Get(id2)
rtest.Assert(t, ok, "blob %v not present", id2)