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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

8
internal/archiver/archive_reader_test.go
View File

@@ -43,9 +43,9 @@ func checkSavedFile(t *testing.T, repo restic.Repository, treeID restic.ID, name
// check blobs
for i, id := range node.Content {
size, err := repo.LookupBlobSize(id, restic.DataBlob)
if err != nil {
t.Fatal(err)
size, found := repo.LookupBlobSize(id, restic.DataBlob)
if !found {
t.Fatal("Failed to find blob", id.Str())
}
buf := restic.NewBlobBuffer(int(size))
@@ -55,7 +55,7 @@ func checkSavedFile(t *testing.T, repo restic.Repository, treeID restic.ID, name
}
buf2 := make([]byte, int(size))
_, err = io.ReadFull(rd, buf2)
_, err := io.ReadFull(rd, buf2)
if err != nil {
t.Fatal(err)
}

4
internal/archiver/archiver.go
View File

@@ -86,8 +86,8 @@ func (arch *Archiver) isKnownBlob(id restic.ID, t restic.BlobType) bool {
arch.knownBlobs.Insert(id)
_, err := arch.repo.Index().Lookup(id, t)
if err == nil {
_, found := arch.repo.Index().Lookup(id, t)
if found {
return true
}