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Merge bitcoin/bitcoin#33602: [IBD] coins: reduce lookups in dbcache layer propagation

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0ac969cddf validation: don't reallocate cache for short-lived CCoinsViewCache (Lőrinc)
c8f5e446dc coins: reduce lookups in dbcache layer propagation (Lőrinc)

Pull request description:

  This change is part of [[IBD] - Tracking PR for speeding up Initial Block Download](https://github.com/bitcoin/bitcoin/pull/32043)

  ### Summary

  Previously, when the parent coins cache had no entry and the child did, `BatchWrite` performed a find followed by `try_emplace`, which resulted in multiple `SipHash` computations and bucket traversals on the common insert path.
  On a different path, these caches were recreated needlessly for every block connection.

  ### Fix for double fetch

  This change uses a single leading `try_emplace` and branches on the returned `inserted` flag. In the `FRESH && SPENT` case (not used in production, only exercised by tests), we erase the just-inserted placeholder (which is constant time with no rehash anyway). Semantics are unchanged for all valid parent/child state combinations.

  This change is a minimal version of [bitcoin/bitcoin@`723c49b` (#32128)](723c49b63b) and draws simplification ideas [bitcoin/bitcoin@`ae76ec7` (#30673)](ae76ec7bcf) and https://github.com/bitcoin/bitcoin/pull/30326.

  ### Fix for temporary cache recreation

  Related to parent cache propagation, the second commit makes it possible to avoid destructuring-recreating-destructuring of these short-live parent caches created for each new block.
  A few temporary `CCoinsViewCache`'s are destructed right after the `Flush()`, therefore it is not necessary to call `ReallocateCache` to recreate them right before they're killed anyway.

  This change was based on a subset of https://github.com/bitcoin/bitcoin/pull/28945, the original authors and relevant commenters were added as coauthors to this version.

  -----

  Reindex-chainstate indicates ~1% speedup.
  <details>
  <summary>Details</summary>

  ```python
  COMMITS="647cdb4f7e8041affed887e2325ee03a91078bb1 0b0c3293ffd75afb27dadc0b28426b40132a8c6b"; \
  STOP=909090; DBCACHE=4500; \
  CC=gcc; CXX=g++; \
  BASE_DIR="/mnt/my_storage"; DATA_DIR="$BASE_DIR/BitcoinData"; LOG_DIR="$BASE_DIR/logs"; \
  (echo ""; for c in $COMMITS; do git fetch -q origin $c && git log -1 --pretty='%h %s' $c || exit 1; done; echo "") && \
  hyperfine \
    --sort command \
    --runs 2 \
    --export-json "$BASE_DIR/rdx-$(sed -E 's/(\w{8})\w+ ?/\1-/g;s/-$//'<<<"$COMMITS")-$STOP-$DBCACHE-$CC.json" \
    --parameter-list COMMIT ${COMMITS// /,} \
    --prepare "killall bitcoind 2>/dev/null; rm -f $DATA_DIR/debug.log; git checkout {COMMIT}; git clean -fxd; git reset --hard && \
      cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release -DENABLE_IPC=OFF && ninja -C build bitcoind && \
      ./build/bin/bitcoind -datadir=$DATA_DIR -stopatheight=$STOP -dbcache=1000 -printtoconsole=0; sleep 20" \
    --cleanup "cp $DATA_DIR/debug.log $LOG_DIR/debug-{COMMIT}-$(date +%s).log" \
    "COMPILER=$CC ./build/bin/bitcoind -datadir=$DATA_DIR -stopatheight=$STOP -dbcache=$DBCACHE -reindex-chainstate -blocksonly -connect=0 -printtoconsole=0"

  647cdb4f7e Merge bitcoin/bitcoin#33311: net: Quiet down logging when router doesn't support natpmp/pcp
  0b0c3293ff validation: don't reallocate cache for short-lived CCoinsViewCache

  Benchmark 1: COMPILER=gcc ./build/bin/bitcoind -datadir=/mnt/my_storage/BitcoinData -stopatheight=909090 -dbcache=4500 -reindex-chainstate -blocksonly -connect=0 -printtoconsole=0 (COMMIT = 647cdb4f7e)
    Time (mean ± σ):     16233.508 s ±  9.501 s    [User: 19064.578 s, System: 951.672 s]
    Range (min … max):   16226.790 s … 16240.226 s    2 runs

  Benchmark 2: COMPILER=gcc ./build/bin/bitcoind -datadir=/mnt/my_storage/BitcoinData -stopatheight=909090 -dbcache=4500 -reindex-chainstate -blocksonly -connect=0 -printtoconsole=0 (COMMIT = 0b0c3293ffd75afb27dadc0b28426b40132a8c6b)
    Time (mean ± σ):     16039.626 s ± 17.284 s    [User: 18870.130 s, System: 950.722 s]
    Range (min … max):   16027.405 s … 16051.848 s    2 runs

  Relative speed comparison
          1.01 ±  0.00  COMPILER=gcc ./build/bin/bitcoind -datadir=/mnt/my_storage/BitcoinData -stopatheight=909090 -dbcache=4500 -reindex-chainstate -blocksonly -connect=0 -printtoconsole=0 (COMMIT = 647cdb4f7e)
          1.00          COMPILER=gcc ./build/bin/bitcoind -datadir=/mnt/my_storage/BitcoinData -stopatheight=909090 -dbcache=4500 -reindex-chainstate -blocksonly -connect=0 -printtoconsole=0 (COMMIT = 0b0c3293ffd75afb27dadc0b28426b40132a8c6b)
  ```

  </details>

ACKs for top commit:
  optout21:
    utACK 0ac969cddf
  achow101:
    ACK 0ac969cddf
  andrewtoth:
    utACK 0ac969cddf
  sedited:
    ACK 0ac969cddf

Tree-SHA512: 9fcc3f1a8314368576a4fba96ca72665527eaa3a97964ab5b39491757f3527147d134f79a5c3456f76c1330c7ef862989d23f764236c5e2563be89a81c1cee47
This commit is contained in:
Ava Chow
2025-12-10 15:02:25 -08:00
parent c1f0a89d9c 0ac969cddf
commit c2975f26d6
5 changed files with 20 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
src/validation.cpp
View File

@@ -2966,7 +2966,7 @@ bool Chainstate::DisconnectTip(BlockValidationState& state, DisconnectedBlockTra
LogError("DisconnectTip(): DisconnectBlock %s failed\n", pindexDelete->GetBlockHash().ToString());
return false;
}
bool flushed = view.Flush();
bool flushed = view.Flush(/*will_reuse_cache=*/false); // local CCoinsViewCache goes out of scope
assert(flushed);
}
LogDebug(BCLog::BENCH, "- Disconnect block: %.2fms\n",
@@ -3101,7 +3101,7 @@ bool Chainstate::ConnectTip(
Ticks<MillisecondsDouble>(time_3 - time_2),
Ticks<SecondsDouble>(m_chainman.time_connect_total),
Ticks<MillisecondsDouble>(m_chainman.time_connect_total) / m_chainman.num_blocks_total);
bool flushed = view.Flush();
bool flushed = view.Flush(/*will_reuse_cache=*/false); // local CCoinsViewCache goes out of scope
assert(flushed);
}
const auto time_4{SteadyClock::now()};
@@ -4895,7 +4895,7 @@ bool Chainstate::ReplayBlocks()
}
cache.SetBestBlock(pindexNew->GetBlockHash());
cache.Flush();
cache.Flush(/*will_reuse_cache=*/false); // local CCoinsViewCache goes out of scope
m_chainman.GetNotifications().progress(bilingual_str{}, 100, false);
return true;
}