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Merge bitcoin/bitcoin#22284: p2p, refactor: performance improvements to ProtectEvictionCandidatesByRatio()

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b1d905c225 p2p: earlier continuation when no remaining eviction candidates (Vasil Dimov)
c9e8d8f9b1 p2p: process more candidates per protection iteration (Jon Atack)
02e411ec45 p2p: iterate eviction protection only on networks having candidates (Jon Atack)
5adb064574 bench: add peer eviction protection benchmarks (Jon Atack)
566357f8f7 refactor: move GetRandomNodeEvictionCandidates() to test utilities (Jon Atack)

Pull request description:

  This follow-up to #21261 improves `ProtectEvictionCandidatesByRatio()` for better performance.

  Benchmarks are added; the performance improvement is between 2x and 5x for the benchmarked cases (CPU 2.50GHz, Turbo off, performance mode, Debian Clang 11 non-debug build).

  ```
  $ ./src/bench/bench_bitcoin -filter="EvictionProtection*.*"
  ```

  The refactored code is well-covered by existing unit tests and also a fuzzer.

  - `$ ./src/test/test_bitcoin -t net_peer_eviction_tests`
  - `$ FUZZ=node_eviction ./src/test/fuzz/fuzz ../qa-assets/fuzz_seed_corpus/node_eviction`

ACKs for top commit:
  klementtan:
    Tested and code review ACK b1d905c2.
  vasild:
    ACK b1d905c225
  jarolrod:
    ACK b1d905c225

Tree-SHA512: a3a6607b9ea2fec138da9780c03f63e177b6712091c5a3ddc3804b896a7585216446310280791f5e20cc023d02d2f03a4139237e12b5c1d7f2a1fa1011610e96
This commit is contained in:
W. J. van der Laan
2021-07-15 14:30:10 +02:00
parent c0224bc962 b1d905c225
commit 21998bc028
6 changed files with 194 additions and 27 deletions
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15
src/net.cpp
View File

@@ -937,14 +937,17 @@ void ProtectEvictionCandidatesByRatio(std::vector<NodeEvictionCandidate>& evicti
size_t num_protected{0};
while (num_protected < max_protect_by_network) {
// Count the number of disadvantaged networks from which we have peers to protect.
auto num_networks = std::count_if(networks.begin(), networks.end(), [](const Net& n) { return n.count; });
if (num_networks == 0) {
break;
}
const size_t disadvantaged_to_protect{max_protect_by_network - num_protected};
const size_t protect_per_network{
std::max(disadvantaged_to_protect / networks.size(), static_cast<size_t>(1))};
const size_t protect_per_network{std::max(disadvantaged_to_protect / num_networks, static_cast<size_t>(1))};
// Early exit flag if there are no remaining candidates by disadvantaged network.
bool protected_at_least_one{false};
for (const Net& n : networks) {
for (Net& n : networks) {
if (n.count == 0) continue;
const size_t before = eviction_candidates.size();
EraseLastKElements(eviction_candidates, CompareNodeNetworkTime(n.is_local, n.id),
@@ -954,10 +957,12 @@ void ProtectEvictionCandidatesByRatio(std::vector<NodeEvictionCandidate>& evicti
const size_t after = eviction_candidates.size();
if (before > after) {
protected_at_least_one = true;
num_protected += before - after;
const size_t delta{before - after};
num_protected += delta;
if (num_protected >= max_protect_by_network) {
break;
}
n.count -= delta;
}
}
if (!protected_at_least_one) {