From f38c5e631ee1bad91a078e454198252ba81910dd Mon Sep 17 00:00:00 2001
From: Jacek Sieka <jacek@status.im>
Date: Thu, 23 May 2024 17:37:51 +0200
Subject: [PATCH] trivial memory-based speedups (#2205)

* trivial memory-based speedups

* HashKey becomes non-ref
* use openArray instead of seq in lots of places
* avoid sequtils.reversed when unnecessary
* add basic perf stats to test_coredb

* copyright
---
 nimbus/db/aristo/aristo_blobify.nim           | 54 ++++++------
 nimbus/db/aristo/aristo_desc.nim              |  7 +-
 .../aristo/aristo_desc/desc_identifiers.nim   | 87 +++++++++----------
 .../aristo/aristo_init/rocks_db/rdb_walk.nim  |  2 +-
 nimbus/db/aristo/aristo_layers.nim            |  8 +-
 nimbus/db/aristo/aristo_path.nim              |  4 +-
 nimbus/db/aristo/aristo_serialise.nim         |  6 +-
 nimbus/db/kvt/kvt_desc.nim                    |  5 ++
 nimbus/db/kvt/kvt_layers.nim                  |  6 +-
 tests/test_coredb/test_chainsync.nim          | 30 ++++++-
 tests/test_coredb/test_helpers.nim            | 10 +++
 11 files changed, 127 insertions(+), 92 deletions(-)

diff --git a/nimbus/db/aristo/aristo_blobify.nim b/nimbus/db/aristo/aristo_blobify.nim
index 8cb0040bf..61dcc7421 100644
--- a/nimbus/db/aristo/aristo_blobify.nim
+++ b/nimbus/db/aristo/aristo_blobify.nim
@@ -21,17 +21,17 @@ import
 # Private helper
 # ------------------------------------------------------------------------------
 
-proc load64(data: Blob; start: var int): Result[uint64,AristoError] =
+proc load64(data: openArray[byte]; start: var int): Result[uint64,AristoError] =
   if data.len < start + 9:
     return err(DeblobPayloadTooShortInt64)
-  let val = uint64.fromBytesBE(data[start ..< start + 8])
+  let val = uint64.fromBytesBE(data.toOpenArray(start, start + 7))
   start += 8
   ok val
 
-proc load256(data: Blob; start: var int): Result[UInt256,AristoError] =
+proc load256(data: openArray[byte]; start: var int): Result[UInt256,AristoError] =
   if data.len < start + 33:
     return err(DeblobPayloadTooShortInt256)
-  let val = UInt256.fromBytesBE(data[start ..< start + 32])
+  let val = UInt256.fromBytesBE(data.toOpenArray(start, start + 31))
   start += 32
   ok val
 
@@ -272,7 +272,7 @@ proc blobify*(vFqs: openArray[(QueueID,QueueID)]): Blob =
 
 # -------------
 
-proc deblobify(data: Blob; pyl: var PayloadRef): Result[void,AristoError] =
+proc deblobify(data: openArray[byte]; pyl: var PayloadRef): Result[void,AristoError] =
   if data.len == 0:
     pyl = PayloadRef(pType: RawData)
     return ok()
@@ -328,7 +328,7 @@ proc deblobify(data: Blob; pyl: var PayloadRef): Result[void,AristoError] =
   pyl = pAcc
   ok()
 
-proc deblobify*(record: Blob; vtx: var VertexRef): Result[void,AristoError] =
+proc deblobify*(record: openArray[byte]; vtx: var VertexRef): Result[void,AristoError] =
   ## De-serialise a data record encoded with `blobify()`. The second
   ## argument `vtx` can be `nil`.
   if record.len < 3:                                  # minimum `Leaf` record
@@ -348,14 +348,14 @@ proc deblobify*(record: Blob; vtx: var VertexRef): Result[void,AristoError] =
       aIny = record.len - 2
     var
       offs = 0
-      access = uint16.fromBytesBE record[aInx..aIny]  # bitmap
+      access = uint16.fromBytesBE record.toOpenArray(aInx, aIny)  # bitmap
       vtxList: array[16,VertexID]
     while access != 0:
       if maxOffset < offs:
         return err(DeblobBranchInxOutOfRange)
       let n = access.firstSetBit - 1
       access.clearBit n
-      vtxList[n] = (uint64.fromBytesBE record[offs ..< offs+8]).VertexID
+      vtxList[n] = (uint64.fromBytesBE record.toOpenArray(offs, offs + 7)).VertexID
       offs += 8
       # End `while`
     vtx = VertexRef(
@@ -370,12 +370,12 @@ proc deblobify*(record: Blob; vtx: var VertexRef): Result[void,AristoError] =
       return err(DeblobExtTooShort)
     if 8 + sLen != rLen:                              # => slen is at least 1
       return err(DeblobExtSizeGarbled)
-    let (isLeaf, pathSegment) = hexPrefixDecode record[8 ..< rLen]
+    let (isLeaf, pathSegment) = hexPrefixDecode record.toOpenArray(8, rLen - 1)
     if isLeaf:
       return err(DeblobExtGotLeafPrefix)
     vtx = VertexRef(
       vType: Extension,
-      eVid:  (uint64.fromBytesBE record[0 ..< 8]).VertexID,
+      eVid:  (uint64.fromBytesBE record.toOpenArray(0, 7)).VertexID,
       ePfx:  pathSegment)
 
   of 3: # `Leaf` vertex
@@ -385,11 +385,11 @@ proc deblobify*(record: Blob; vtx: var VertexRef): Result[void,AristoError] =
       pLen = rLen - sLen                              # payload length
     if rLen < sLen:
       return err(DeblobLeafSizeGarbled)
-    let (isLeaf, pathSegment) = hexPrefixDecode record[pLen ..< rLen]
+    let (isLeaf, pathSegment) = hexPrefixDecode record.toOpenArray(pLen, rLen-1)
     if not isLeaf:
       return err(DeblobLeafGotExtPrefix)
     var pyl: PayloadRef
-    ? record[0 ..< pLen].deblobify(pyl)
+    ? record.toOpenArray(0, pLen - 1).deblobify(pyl)
     vtx = VertexRef(
       vType: Leaf,
       lPfx:  pathSegment,
@@ -399,14 +399,14 @@ proc deblobify*(record: Blob; vtx: var VertexRef): Result[void,AristoError] =
     return err(DeblobUnknown)
   ok()
 
-proc deblobify*(data: Blob; T: type VertexRef): Result[T,AristoError] =
+proc deblobify*(data: openArray[byte]; T: type VertexRef): Result[T,AristoError] =
   ## Variant of `deblobify()` for vertex deserialisation.
   var vtx = T(nil) # will be auto-initialised
   ? data.deblobify vtx
   ok vtx
 
 
-proc deblobify*(data: Blob; vGen: var seq[VertexID]): Result[void,AristoError] =
+proc deblobify*(data: openArray[byte]; vGen: var seq[VertexID]): Result[void,AristoError] =
   ## De-serialise the data record encoded with `blobify()` into the vertex ID
   ## generator argument `vGen`.
   if data.len == 0:
@@ -418,10 +418,10 @@ proc deblobify*(data: Blob; vGen: var seq[VertexID]): Result[void,AristoError] =
       return err(DeblobWrongType)
     for n in 0 ..< (data.len div 8):
       let w = n * 8
-      vGen.add (uint64.fromBytesBE data[w ..< w + 8]).VertexID
+      vGen.add (uint64.fromBytesBE data.toOpenArray(w, w+7)).VertexID
   ok()
 
-proc deblobify*(data: Blob; T: type seq[VertexID]): Result[T,AristoError] =
+proc deblobify*(data: openArray[byte]; T: type seq[VertexID]): Result[T,AristoError] =
   ## Variant of `deblobify()` for deserialising the vertex ID generator state
   var vGen: seq[VertexID]
   ? data.deblobify vGen
@@ -436,25 +436,25 @@ proc deblobify*(data: Blob; filter: var FilterRef): Result[void,AristoError] =
 
   func deblob(data: openArray[byte]; shortKey: bool): Result[HashKey,void] =
     if shortKey:
-      HashKey.fromBytes data[1 .. min(data[0],31)]
+      HashKey.fromBytes data.toOpenArray(1, min(int data[0],31))
     else:
       HashKey.fromBytes data
 
   let f = FilterRef()
-  f.fid = (uint64.fromBytesBE data[0 ..< 8]).FilterID
+  f.fid = (uint64.fromBytesBE data.toOpenArray(0, 7)).FilterID
   (addr f.src.data[0]).copyMem(unsafeAddr data[8], 32)
   (addr f.trg.data[0]).copyMem(unsafeAddr data[40], 32)
 
   let
-    nVids = uint32.fromBytesBE data[72 ..< 76]
-    nTriplets = uint32.fromBytesBE data[76 ..< 80]
+    nVids = uint32.fromBytesBE data.toOpenArray(72, 75)
+    nTriplets = uint32.fromBytesBE data.toOpenArray(76, 79)
     nTrplStart = (80 + nVids * 8).int
 
   if data.len < nTrplStart:
     return err(DeblobFilterGenTooShort)
   for n in 0 ..< nVids:
     let w = 80 + n * 8
-    f.vGen.add (uint64.fromBytesBE data[w ..< w + 8]).VertexID
+    f.vGen.add (uint64.fromBytesBE data.toOpenArray(int w, int w+7)).VertexID
 
   var offs = nTrplStart
   for n in 0 ..< nTriplets:
@@ -463,20 +463,20 @@ proc deblobify*(data: Blob; filter: var FilterRef): Result[void,AristoError] =
 
     let
       keyFlag = data[offs] shr 6
-      vtxFlag = ((uint32.fromBytesBE data[offs ..< offs+4]) and 0x3fff_ffff).int
+      vtxFlag = ((uint32.fromBytesBE data.toOpenArray(offs, offs+3)) and 0x3fff_ffff).int
       vLen = if vtxFlag == 0x3fff_ffff: 0 else: vtxFlag
     if keyFlag == 0 and vtxFlag == 0:
       return err(DeblobFilterTrpVtxSizeGarbled) # no blind records
     offs = offs + 4
 
-    let vid = (uint64.fromBytesBE data[offs ..< offs + 8]).VertexID
+    let vid = (uint64.fromBytesBE data.toOpenArray(offs, offs+7)).VertexID
     offs = offs + 8
 
     if data.len < offs + (1 < keyFlag).ord * 32 + vLen:
       return err(DeblobFilterTrpTooShort)
 
     if 1 < keyFlag:
-      f.kMap[vid] = data[offs ..< offs + 32].deblob(keyFlag == 3).valueOr:
+      f.kMap[vid] = data.toOpenArray(offs, offs+31).deblob(keyFlag == 3).valueOr:
         return err(DeblobHashKeyExpected)
       offs = offs + 32
     elif keyFlag == 1:
@@ -486,7 +486,7 @@ proc deblobify*(data: Blob; filter: var FilterRef): Result[void,AristoError] =
       f.sTab[vid] = VertexRef(nil)
     elif 0 < vLen:
       var vtx: VertexRef
-      ? data[offs ..< offs + vLen].deblobify vtx
+      ? data.toOpenArray(offs, offs + vLen - 1).deblobify vtx
       f.sTab[vid] = vtx
       offs = offs + vLen
 
@@ -518,8 +518,8 @@ proc deblobify*(
     for n in 0 ..< (data.len div 16):
       let
         w = n * 16
-        a = (uint64.fromBytesBE data[w + 0 ..< w + 8]).QueueID
-        b = (uint64.fromBytesBE data[w + 8 ..< w + 16]).QueueID
+        a = (uint64.fromBytesBE data.toOpenArray(w, w + 7)).QueueID
+        b = (uint64.fromBytesBE data.toOpenArray(w + 8, w + 15)).QueueID
       vFqs.add (a,b)
   ok()
 
diff --git a/nimbus/db/aristo/aristo_desc.nim b/nimbus/db/aristo/aristo_desc.nim
index 8502dd325..e23c592e1 100644
--- a/nimbus/db/aristo/aristo_desc.nim
+++ b/nimbus/db/aristo/aristo_desc.nim
@@ -98,7 +98,7 @@ func getOrVoid*[W](tab: Table[W,HashSet[VertexID]]; w: W): HashSet[VertexID] =
 # --------
 
 func isValid*(vtx: VertexRef): bool =
-  vtx != VertexRef(nil) 
+  vtx != VertexRef(nil)
 
 func isValid*(nd: NodeRef): bool =
   nd != NodeRef(nil)
@@ -260,6 +260,11 @@ proc forgetOthers*(db: AristoDbRef): Result[void,AristoError] =
     db.dudes = DudesRef(nil)
   ok()
 
+iterator rstack*(db: AristoDbRef): LayerRef =
+  # Stack in reverse order
+  for i in 0..<db.stack.len:
+    yield db.stack[db.stack.len - i - 1]
+
 # ------------------------------------------------------------------------------
 # End
 # ------------------------------------------------------------------------------
diff --git a/nimbus/db/aristo/aristo_desc/desc_identifiers.nim b/nimbus/db/aristo/aristo_desc/desc_identifiers.nim
index a18b359ff..77711f8ed 100644
--- a/nimbus/db/aristo/aristo_desc/desc_identifiers.nim
+++ b/nimbus/db/aristo/aristo_desc/desc_identifiers.nim
@@ -53,11 +53,11 @@ type
     ## `Hash256` type of the Keccak hash of an empty `Blob` (see constant
     ## `EMPTY_ROOT_HASH`.)
     ##
-    case isHash: bool
-    of true:
-      key: Hash256                   ## Merkle hash tacked to a vertex
-    else:
-      blob: Blob                     ## Optionally encoded small node data
+    ## For performance, we avoid storing blobs as `seq`, instead storing their
+    ## length and sharing the data "space".
+    ## TODO can we skip one byte of hash and reduce this type to 32 bytes?
+    buf: array[32, byte] # Either Hash256 or blob data, depending on `len`
+    len: int8 # length in the case of blobs, or 32 when it's a hash
 
   PathID* = object
     ## Path into the `Patricia Trie`. This is a chain of maximal 64 nibbles
@@ -198,15 +198,18 @@ func `==`*(a, b: PathID): bool =
 func cmp*(a, b: PathID): int =
   if a < b: -1 elif b < a: 1 else: 0
 
+template data*(lid: HashKey): openArray[byte] =
+  lid.buf.toOpenArray(0, lid.len - 1)
+
 func to*(lid: HashKey; T: type PathID): T =
   ## Helper to bowrrow certain properties from `PathID`
-  if lid.isHash:
-    PathID(pfx: UInt256.fromBytesBE lid.key.data, length: 64)
-  elif 0 < lid.blob.len:
-    doAssert lid.blob.len < 32
+  if lid.len == 32:
+    PathID(pfx: UInt256.fromBytesBE lid.data, length: 64)
+  elif 0 < lid.len:
+    doAssert lid.len < 32
     var a32: array[32,byte]
-    (addr a32[0]).copyMem(unsafeAddr lid.blob[0], lid.blob.len)
-    PathID(pfx: UInt256.fromBytesBE a32, length: 2 * lid.blob.len.uint8)
+    (addr a32[0]).copyMem(unsafeAddr lid.data[0], lid.len)
+    PathID(pfx: UInt256.fromBytesBE a32, length: 2 * lid.len.uint8)
   else:
     PathID()
 
@@ -215,7 +218,7 @@ func to*(lid: HashKey; T: type PathID): T =
 # ------------------------------------------------------------------------------
 
 func len*(lid: HashKey): int =
-  if lid.isHash: 32 else: lid.blob.len
+  lid.len.int # if lid.isHash: 32 else: lid.blob.len
 
 func fromBytes*(T: type HashKey; data: openArray[byte]): Result[T,void] =
   ## Write argument `data` of length 0 or between 2 and 32 bytes as a `HashKey`.
@@ -228,13 +231,16 @@ func fromBytes*(T: type HashKey; data: openArray[byte]): Result[T,void] =
   ##
   if data.len == 32:
     var lid: T
-    lid.isHash = true
-    (addr lid.key.data[0]).copyMem(unsafeAddr data[0], data.len)
+    lid.len = 32
+    (addr lid.data[0]).copyMem(unsafeAddr data[0], data.len)
     return ok lid
   if data.len == 0:
     return ok HashKey()
   if 1 < data.len and data.len < 32 and data[0].int == 0xbf + data.len:
-    return ok T(isHash: false, blob: @data)
+    var lid: T
+    lid.len = int8 data.len
+    (addr lid.data[0]).copyMem(unsafeAddr data[0], data.len)
+    return ok lid
   err()
 
 func `<`*(a, b: HashKey): bool =
@@ -242,16 +248,11 @@ func `<`*(a, b: HashKey): bool =
   a.to(PathID) < b.to(PathID)
 
 func `==`*(a, b: HashKey): bool =
-  if a.isHash != b.isHash:
-    false
-  elif a.isHash:
-    a.key == b.key
-  else:
-    a.blob == b.blob
+  a.data == b.data
 
 func cmp*(a, b: HashKey): int =
   ## Slow, but useful for debug sorting
-  if a < b: -1 elif b < a: 1 else: 0
+  cmp(a.data, b.data)
 
 # ------------------------------------------------------------------------------
 # Public helpers: `LeafTie` ordered scalar data model
@@ -292,16 +293,13 @@ func cmp*(a, b: LeafTie): int =
 # Public helpers: Reversible conversions between `PathID`, `HashKey`, etc.
 # ------------------------------------------------------------------------------
 
-func to*(key: HashKey; T: type Blob): T =
+func to*(key: HashKey; T: type Blob): T {.deprecated.} =
   ## Rewrite `HashKey` argument as `Blob` type of length between 0 and 32. A
   ## blob of length 32 is taken as a representation of a `HashKey` type while
   ## samller blobs are expected to represent an RLP encoded small node.
-  if key.isHash:
-    @(key.key.data)
-  else:
-    key.blob
+  @(key.data)
 
-func `@`*(lid: HashKey): Blob =
+func `@`*(lid: HashKey): Blob {.deprecated.} =
   ## Variant of `to(Blob)`
   lid.to(Blob)
 
@@ -323,10 +321,10 @@ func `@`*(pid: PathID): Blob =
 func to*(lid: HashKey; T: type Hash256): T =
   ## Returns the `Hash236` key if available, otherwise the Keccak hash of
   ## the `Blob` version.
-  if lid.isHash:
-    lid.key
-  elif 0 < lid.blob.len:
-    lid.blob.keccakHash
+  if lid.len == 32:
+    Hash256(data: lid.buf)
+  elif 0 < lid.len:
+    lid.data.keccakHash
   else:
     EMPTY_ROOT_HASH
 
@@ -336,7 +334,7 @@ func to*(key: Hash256; T: type HashKey): T =
   if key == EMPTY_ROOT_HASH:
     T()
   else:
-    T(isHash: true, key: key)
+    T(len: 32, buf: key.data)
 
 func to*(n: SomeUnsignedInt|UInt256; T: type PathID): T =
   ## Representation of a scalar as `PathID` (preserving full information)
@@ -349,11 +347,14 @@ func to*(n: SomeUnsignedInt|UInt256; T: type PathID): T =
 func digestTo*(data: openArray[byte]; T: type HashKey): T =
   ## For argument `data` with length smaller than 32, import them as-is into
   ## the result. Otherwise import the Keccak hash of the argument `data`.
-  if data.len < 32:
-    result.blob = @data
+  if data.len == 0:
+    result.len = 0
+  elif data.len < 32:
+    result.len = int8 data.len
+    (addr result.data[0]).copyMem(unsafeAddr data[0], data.len)
   else:
-    result.isHash = true
-    result.key = data.keccakHash
+    result.len = 32
+    result.buf = data.keccakHash.data
 
 func normal*(a: PathID): PathID =
   ## Normalise path ID representation
@@ -376,12 +377,7 @@ func hash*(a: PathID): Hash =
 
 func hash*(a: HashKey): Hash =
   ## Table/KeyedQueue mixin
-  var h: Hash = 0
-  if a.isHash:
-    h = h !& a.key.hash
-  else:
-    h = h !& a.blob.hash
-  !$h
+  hash(a.data)
 
 # ------------------------------------------------------------------------------
 # Miscellaneous helpers
@@ -415,10 +411,7 @@ func `$`*(key: Hash256): string =
     w.toHex
 
 func `$`*(key: HashKey): string =
-  if key.isHash:
-    $key.key
-  else:
-    key.blob.toHex & "[#" & $key.blob.len & "]"
+  toHex(key.data)
 
 func `$`*(a: PathID): string =
   if a.pfx.isZero.not:
diff --git a/nimbus/db/aristo/aristo_init/rocks_db/rdb_walk.nim b/nimbus/db/aristo/aristo_init/rocks_db/rdb_walk.nim
index 09f0e0854..6bdfb2937 100644
--- a/nimbus/db/aristo/aristo_init/rocks_db/rdb_walk.nim
+++ b/nimbus/db/aristo/aristo_init/rocks_db/rdb_walk.nim
@@ -54,7 +54,7 @@ iterator walk*(
           break walkBody
         let
           pfx = StorageType(key[0])
-          id = uint64.fromBytesBE key[1..^1]
+          id = uint64.fromBytesBE key.toOpenArray(1, key.len - 1)
         yield (pfx, id, val)
 
 
diff --git a/nimbus/db/aristo/aristo_layers.nim b/nimbus/db/aristo/aristo_layers.nim
index 1e91e2c92..0411cc354 100644
--- a/nimbus/db/aristo/aristo_layers.nim
+++ b/nimbus/db/aristo/aristo_layers.nim
@@ -69,7 +69,7 @@ proc layersGetVtx*(db: AristoDbRef; vid: VertexID): Result[VertexRef,void] =
   if db.top.delta.sTab.hasKey vid:
     return ok(db.top.delta.sTab.getOrVoid vid)
 
-  for w in db.stack.reversed:
+  for w in db.rstack:
     if w.delta.sTab.hasKey vid:
       return ok(w.delta.sTab.getOrVoid vid)
 
@@ -89,7 +89,7 @@ proc layersGetKey*(db: AristoDbRef; vid: VertexID): Result[HashKey,void] =
     # dirty, there is an empty `kMap[]` entry on this layer.
     return ok(db.top.delta.kMap.getOrVoid vid)
 
-  for w in db.stack.reversed:
+  for w in db.rstack:
     if w.delta.kMap.hasKey vid:
       # Same reasoning as above regarding the `dirty` flag.
       return ok(w.delta.kMap.getOrVoid vid)
@@ -233,7 +233,7 @@ iterator layersWalkVtx*(
     yield (vid,vtx)
     seen.incl vid
 
-  for w in db.stack.reversed:
+  for w in db.rstack:
     for (vid,vtx) in w.delta.sTab.pairs:
       if vid notin seen:
         yield (vid,vtx)
@@ -258,7 +258,7 @@ iterator layersWalkKey*(
     yield (vid,key)
     seen.incl vid
 
-  for w in db.stack.reversed:
+  for w in db.rstack:
     for (vid,key) in w.delta.kMap.pairs:
       if vid notin seen:
         yield (vid,key)
diff --git a/nimbus/db/aristo/aristo_path.nim b/nimbus/db/aristo/aristo_path.nim
index 07c03f047..d70eae908 100644
--- a/nimbus/db/aristo/aristo_path.nim
+++ b/nimbus/db/aristo/aristo_path.nim
@@ -45,9 +45,9 @@ func pathAsBlob*(tag: PathID): Blob =
   ## used to index database leaf values can be represented as `Blob`, i.e.
   ## `PathID` type paths with an even number of nibbles.
   if 0 < tag.length:
-    let key = @(tag.pfx.toBytesBE)
+    let key = tag.pfx.toBytesBE
     if 64 <= tag.length:
-      return key
+      return @key
     else:
       return key[0 .. (tag.length - 1) div 2]
 
diff --git a/nimbus/db/aristo/aristo_serialise.nim b/nimbus/db/aristo/aristo_serialise.nim
index 9a2ad4a4e..190784b4c 100644
--- a/nimbus/db/aristo/aristo_serialise.nim
+++ b/nimbus/db/aristo/aristo_serialise.nim
@@ -1,5 +1,5 @@
 # nimbus-eth1
-# Copyright (c) 2023 Status Research & Development GmbH
+# Copyright (c) 2023-2024 Status Research & Development GmbH
 # Licensed under either of
 #  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
 #    http://www.apache.org/licenses/LICENSE-2.0)
@@ -133,9 +133,9 @@ proc append*(writer: var RlpWriter; node: NodeRef) =
   ## list.
   func addHashKey(w: var RlpWriter; key: HashKey) =
     if 1 < key.len and key.len < 32:
-      w.appendRawBytes @key
+      w.appendRawBytes key.data
     else:
-      w.append @key
+      w.append key.data
 
   if node.error != AristoError(0):
     writer.startList(0)
diff --git a/nimbus/db/kvt/kvt_desc.nim b/nimbus/db/kvt/kvt_desc.nim
index 872162041..424e31a8f 100644
--- a/nimbus/db/kvt/kvt_desc.nim
+++ b/nimbus/db/kvt/kvt_desc.nim
@@ -191,6 +191,11 @@ proc forgetOthers*(db: KvtDbRef): Result[void,KvtError] =
     db.dudes = DudesRef(nil)
   ok()
 
+iterator rstack*(db: KvtDbRef): LayerRef =
+  # Stack in reverse order
+  for i in 0..<db.stack.len:
+    yield db.stack[db.stack.len - i - 1]
+
 # ------------------------------------------------------------------------------
 # End
 # ------------------------------------------------------------------------------
diff --git a/nimbus/db/kvt/kvt_layers.nim b/nimbus/db/kvt/kvt_layers.nim
index f6a9e1929..bb417dbbf 100644
--- a/nimbus/db/kvt/kvt_layers.nim
+++ b/nimbus/db/kvt/kvt_layers.nim
@@ -37,7 +37,7 @@ proc layersHasKey*(db: KvtDbRef; key: openArray[byte]): bool =
   if db.top.delta.sTab.hasKey @key:
     return true
 
-  for w in db.stack.reversed:
+  for w in db.rstack:
     if w.delta.sTab.hasKey @key:
       return true
 
@@ -49,7 +49,7 @@ proc layersGet*(db: KvtDbRef; key: openArray[byte]): Result[Blob,void] =
   if db.top.delta.sTab.hasKey @key:
     return ok(db.top.delta.sTab.getOrVoid @key)
 
-  for w in db.stack.reversed:
+  for w in db.rstack:
     if w.delta.sTab.hasKey @key:
       return ok(w.delta.sTab.getOrVoid @key)
 
@@ -101,7 +101,7 @@ iterator layersWalk*(
     yield (key,val)
     seen.incl key
 
-  for w in db.stack.reversed:
+  for w in db.rstack:
     for (key,val) in w.delta.sTab.pairs:
       if key notin seen:
         yield (key,val)
diff --git a/tests/test_coredb/test_chainsync.nim b/tests/test_coredb/test_chainsync.nim
index 3b1047673..4bebb74c9 100644
--- a/tests/test_coredb/test_chainsync.nim
+++ b/tests/test_coredb/test_chainsync.nim
@@ -199,6 +199,20 @@ proc test_chainSync*(
   # This will enable printing the `era1` covered block ranges (if any)
   undump_blocks_era1.noisy = noisy
 
+  var
+    blocks = 0
+    total = 0
+    begin = toUnixFloat(getTime())
+    sample = begin
+
+  template sayPerf =
+    if blocks > 0:
+      total += blocks
+      let done {.inject.} = toUnixFloat(getTime())
+      noisy.say "", &"{blocks:3} blocks, {(done-sample):2.3}s, {(blocks.float / (done-sample)):4.3f} b/s, avg {(total.float / (done-begin)):4.3f} b/s"
+      blocks = 0
+      sample = done
+
   for w in files.undumpBlocks(least = start):
     let (fromBlock, toBlock) = (w[0][0].blockNumber, w[0][^1].blockNumber)
     if fromBlock == 0.u256:
@@ -209,9 +223,12 @@ proc test_chainSync*(
     if toBlock < lastBlock:
       # Message if `[fromBlock,toBlock]` contains a multiple of `sayBlocks`
       if fromBlock + (toBlock mod sayBlocks.u256) <= toBlock:
-        noisy.say "***", &"processing ...[#{fromBlock},#{toBlock}]..."
+        sayPerf
+
+        noisy.whisper "***", &"processing ...[#{fromBlock:>8},#{toBlock:>8}]..."
         if enaLogging:
           noisy.startLogging(w[0][0].blockNumber)
+
       noisy.stopLoggingAfter():
         let runPersistBlocksRc = chain.persistBlocks(w[0], w[1])
         xCheck runPersistBlocksRc == ValidationResult.OK:
@@ -222,6 +239,7 @@ proc test_chainSync*(
             com.db.trackNewApi = false
             com.db.trackLedgerApi = false
             discard chain.persistBlocks(w[0], w[1])
+      blocks += w[0].len
       continue
 
     # Last group or single block
@@ -241,7 +259,8 @@ proc test_chainSync*(
       let
         headers1 = w[0][0 ..< pivot]
         bodies1 = w[1][0 ..< pivot]
-      noisy.say "***", &"processing {dotsOrSpace}[#{fromBlock},#{lastBlock-1}]"
+      sayPerf
+      noisy.whisper "***", &"processing {dotsOrSpace}[#{fromBlock:>8},#{(lastBlock-1):>8}]"
       let runPersistBlocks1Rc = chain.persistBlocks(headers1, bodies1)
       xCheck runPersistBlocks1Rc == ValidationResult.OK
       dotsOrSpace = "   "
@@ -251,16 +270,19 @@ proc test_chainSync*(
       let
         headers0 = headers9[0..0]
         bodies0 = bodies9[0..0]
-      noisy.say "***", &"processing {dotsOrSpace}[#{lastBlock},#{lastBlock}]"
+      sayPerf
+      noisy.whisper "***", &"processing {dotsOrSpace}[#{lastBlock:>8},#{lastBlock:>8}]"
       noisy.stopLoggingAfter():
         let runPersistBlocks0Rc = chain.persistBlocks(headers0, bodies0)
         xCheck runPersistBlocks0Rc == ValidationResult.OK
     else:
-      noisy.say "***", &"processing {dotsOrSpace}[#{lastBlock},#{toBlock}]"
+      sayPerf
+      noisy.whisper "***", &"processing {dotsOrSpace}[#{lastBlock:>8},#{toBlock:>8}]"
       noisy.stopLoggingAfter():
         let runPersistBlocks9Rc = chain.persistBlocks(headers9, bodies9)
         xCheck runPersistBlocks9Rc == ValidationResult.OK
     break
+  sayPerf
 
   true
 
diff --git a/tests/test_coredb/test_helpers.nim b/tests/test_coredb/test_helpers.nim
index 05cf5cd25..7c66e31b2 100644
--- a/tests/test_coredb/test_helpers.nim
+++ b/tests/test_coredb/test_helpers.nim
@@ -53,6 +53,16 @@ proc say*(noisy = false; pfx = "***"; args: varargs[string, `$`]) =
     else:
       echo pfx, args.toSeq.join
 
+proc whisper*(noisy = false; pfx = "***"; args: varargs[string, `$`]) =
+  if noisy:
+    if args.len == 0:
+      stdout.write("*** ", pfx)
+    elif 0 < pfx.len and pfx[^1] != ' ':
+      stdout.write(pfx, " ", args.toSeq.join)
+    else:
+      stdout.write(pfx, args.toSeq.join)
+    stdout.flushFile()
+
 proc toPfx*(indent: int): string =
   "\n" & " ".repeat(indent)