Halve FC memory usage

Blocks are getting stored both in BlockRef and in TxFrame - this is the
less invasive change that delays storing block contents in TxFrame until
it's time to update the base - the better option for the future is
likely to not store the full block in BlockRef (and instead load it from
TxFrame on demand)

Author: arnetheduck

execution_chain/core/chain/forked_chain.nim

@@ -327,6 +327,17 @@ something else needs attention! Shutting down to preserve the database - restart
 with --debug-eager-state-root."""
 
   c.com.db.persist(base.txFrame)
+  block:
+    # Write block contents to txFrame at the last moment - otherwise, they would
+    # stay both in BlockRef and TxFrame memory
+    # TODO probably makes sense to do it the other way around, removing blk
+    #      from BlockRef
+    var blk = base
+    while blk.isOk:
+      c.writeBaggage(blk.blk, blk.hash, blk.txFrame, blk.receipts)
+      blk = blk.parent
+
+  c.com.db.persist(base.txFrame, Opt.some(base.stateRoot))
 
   # Update baseTxFrame when we about to yield to the event loop
   # and prevent other modules accessing expired baseTxFrame.
@@ -481,9 +492,7 @@ proc validateBlock(c: ForkedChainRef,
     txFrame.dispose()
     return err(error)
 
-  c.writeBaggage(blk, blkHash, txFrame, receipts)
-
-  c.updateSnapshot(blk, txFrame)
+  c.updateSnapshot(blk.header.number, txFrame)
 
   let newBlock = c.appendBlock(parent, blk, blkHash, txFrame, move(receipts))
 

execution_chain/core/chain/forked_chain/chain_private.nim

@@ -35,8 +35,8 @@ proc writeBaggage*(c: ForkedChainRef,
       header.withdrawalsRoot.expect("WithdrawalsRoot should be verified before"),
       blk.withdrawals.get)
 
-template updateSnapshot*(c: ForkedChainRef,
-            blk: Block,
+proc updateSnapshot*(c: ForkedChainRef,
+            number: BlockNumber,
             txFrame: CoreDbTxRef) =
   let pos = c.lastSnapshotPos
   c.lastSnapshotPos = (c.lastSnapshotPos + 1) mod c.lastSnapshots.len
@@ -51,7 +51,7 @@ template updateSnapshot*(c: ForkedChainRef,
   # Checkpoint creates a snapshot of ancestor changes in txFrame - it is an
   # expensive operation, specially when creating a new branch (ie when blk
   # is being applied to a block that is currently not a head)
-  txFrame.checkpoint(blk.header.number)
+  txFrame.checkpoint(number)
 
   c.lastSnapshots[pos] = txFrame
 

execution_chain/core/chain/forked_chain/chain_serialize.nim

@@ -131,7 +131,7 @@ proc replayBlock(fc: ForkedChainRef;
     return err(error)
 
   fc.writeBaggage(blk.blk, blk.hash, txFrame, receipts)
-  fc.updateSnapshot(blk.blk, txFrame)
+  fc.updateSnapshot(blk.blk.header.number, txFrame)
 
   blk.txFrame = txFrame
   blk.receipts = move(receipts)