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repository/master_index: Optimize Index.Lookup()

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When looking up a blob in the master index, with several
indexes present in the master index, a significant amount of time
is spent generating errors for each failed lookup.  However, these
errors are often used to check if a blob is present, but the contents
are not inspected making the overhead of the error not useful.

Instead, change Index.Lookup (and Index.LookupSize) to instead return
a boolean denoting if the blob was found instead of an error.  Also change
all the calls to these functions to handle the new function signature.

benchmark                                            old ns/op     new ns/op     delta
BenchmarkMasterIndexLookupSingleIndex-6              820           897           +9.39%
BenchmarkMasterIndexLookupMultipleIndex-6            12821         2001          -84.39%
BenchmarkMasterIndexLookupSingleIndexUnknown-6       5378          492           -90.85%
BenchmarkMasterIndexLookupMultipleIndexUnknown-6     17026         1649          -90.31%

benchmark                                            old allocs     new allocs     delta
BenchmarkMasterIndexLookupSingleIndex-6              9              9              +0.00%
BenchmarkMasterIndexLookupMultipleIndex-6            59             19             -67.80%
BenchmarkMasterIndexLookupSingleIndexUnknown-6       22             6              -72.73%
BenchmarkMasterIndexLookupMultipleIndexUnknown-6     72             16             -77.78%

benchmark                                            old bytes     new bytes     delta
BenchmarkMasterIndexLookupSingleIndex-6              160           160           +0.00%
BenchmarkMasterIndexLookupMultipleIndex-6            3200          240           -92.50%
BenchmarkMasterIndexLookupSingleIndexUnknown-6       1232          48            -96.10%
BenchmarkMasterIndexLookupMultipleIndexUnknown-6     4272          128           -97.00%
This commit is contained in:
Matthew Dawson
2018-01-12 01:20:12 -05:00
parent ebce4b2581
commit df2c03a6a4
15 changed files with 192 additions and 68 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
internal/repository/index.go
View File

@@ -110,7 +110,7 @@ func (idx *Index) Store(blob restic.PackedBlob) {
}
// Lookup queries the index for the blob ID and returns a restic.PackedBlob.
func (idx *Index) Lookup(id restic.ID, tpe restic.BlobType) (blobs []restic.PackedBlob, err error) {
func (idx *Index) Lookup(id restic.ID, tpe restic.BlobType) (blobs []restic.PackedBlob, found bool) {
idx.m.Lock()
defer idx.m.Unlock()
@@ -136,11 +136,11 @@ func (idx *Index) Lookup(id restic.ID, tpe restic.BlobType) (blobs []restic.Pack
blobs = append(blobs, blob)
}
return blobs, nil
return blobs, true
}
debug.Log("id %v not found", id.Str())
return nil, errors.Errorf("id %v not found in index", id)
return nil, false
}
// ListPack returns a list of blobs contained in a pack.
@@ -180,13 +180,13 @@ func (idx *Index) Has(id restic.ID, tpe restic.BlobType) bool {
// LookupSize returns the length of the plaintext content of the blob with the
// given id.
func (idx *Index) LookupSize(id restic.ID, tpe restic.BlobType) (plaintextLength uint, err error) {
blobs, err := idx.Lookup(id, tpe)
if err != nil {
return 0, err
func (idx *Index) LookupSize(id restic.ID, tpe restic.BlobType) (plaintextLength uint, found bool) {
blobs, found := idx.Lookup(id, tpe)
if !found {
return 0, found
}
return uint(restic.PlaintextLength(int(blobs[0].Length))), nil
return uint(restic.PlaintextLength(int(blobs[0].Length))), true
}
// Supersedes returns the list of indexes this index supersedes, if any.