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dedups packets using an atomic bloom filter (#30726) 

Current Deduper implementation uses many bits per entry:
https://github.com/solana-labs/solana/blob/65cd55261/perf/src/deduper.rs#L70-L73
and may be saturated quickly. It also lacks api to specify desired false
positive rate.

The commit instead uses an atomic bloom filter with K hash functions.
The false positive rate is obtained by tracking popcount of bits.
This commit is contained in:
behzad nouri 2023-03-16 16:45:42 +00:00 committed by GitHub
parent 17ba051e1f
commit 7a7b020580
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
5 changed files with 158 additions and 88 deletions
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2
Cargo.lock generated
View File

@ -6026,6 +6026,7 @@ dependencies = [
"matches",
"nix",
"rand 0.7.3",
"rand_chacha 0.2.2",
"rayon",
"serde",
"solana-logger 1.16.0",
@ -6033,6 +6034,7 @@ dependencies = [
"solana-rayon-threadlimit",
"solana-sdk 1.16.0",
"solana-vote-program",
"test-case",
]
[[package]]

11
core/src/sigverify_stage.rs
View File

@ -290,7 +290,7 @@ impl SigVerifyStage {
}
fn verifier<T: SigVerifier>(
deduper: &Deduper,
deduper: &Deduper<2>,
recvr: &FindPacketSenderStakeReceiver,
verifier: &mut T,
stats: &mut SigVerifierStats,
@ -410,13 +410,16 @@ impl SigVerifyStage {
let mut stats = SigVerifierStats::default();
let mut last_print = Instant::now();
const MAX_DEDUPER_AGE: Duration = Duration::from_secs(2);
const MAX_DEDUPER_ITEMS: u32 = 1_000_000;
const DEDUPER_FALSE_POSITIVE_RATE: f64 = 0.001;
const DEDUPER_NUM_BITS: u64 = 63_999_979;
Builder::new()
.name("solSigVerifier".to_string())
.spawn(move || {
let mut deduper = Deduper::new(MAX_DEDUPER_ITEMS, MAX_DEDUPER_AGE);
let mut rng = rand::thread_rng();
let mut deduper =
Deduper::<2>::new(&mut rng, DEDUPER_FALSE_POSITIVE_RATE, DEDUPER_NUM_BITS);
loop {
deduper.reset();
deduper.maybe_reset(&mut rng, &MAX_DEDUPER_AGE);
if let Err(e) =
Self::verifier(&deduper, &packet_receiver, &mut verifier, &mut stats)
{

2
perf/Cargo.toml
View File

@ -37,7 +37,9 @@ name = "solana_perf"
[dev-dependencies]
matches = { workspace = true }
rand_chacha = "0.2.2"
solana-logger = { workspace = true }
test-case = { workspace = true }
[[bench]]
name = "sigverify"

14
perf/benches/dedup.rs
View File

@ -24,10 +24,13 @@ fn test_packet_with_size(size: usize, rng: &mut ThreadRng) -> Vec<u8> {
fn do_bench_dedup_packets(bencher: &mut Bencher, mut batches: Vec<PacketBatch>) {
// verify packets
let mut deduper = Deduper::new(1_000_000, Duration::from_millis(2_000));
let mut rng = rand::thread_rng();
let mut deduper = Deduper::<2>::new(
&mut rng, /*false_positive_rate:*/ 0.001, /*num_bits:*/ 63_999_979,
);
bencher.iter(|| {
let _ans = deduper.dedup_packets_and_count_discards(&mut batches, |_, _, _| ());
deduper.reset();
deduper.maybe_reset(&mut rng, /*reset_cycle:*/ &Duration::from_secs(2));
batches
.iter_mut()
.for_each(|b| b.iter_mut().for_each(|p| p.meta_mut().set_discard(false)));
@ -112,8 +115,11 @@ fn bench_dedup_baseline(bencher: &mut Bencher) {
#[bench]
#[ignore]
fn bench_dedup_reset(bencher: &mut Bencher) {
let mut deduper = Deduper::new(1_000_000, Duration::from_millis(0));
let mut rng = rand::thread_rng();
let mut deduper = Deduper::<2>::new(
&mut rng, /*false_positive_rate:*/ 0.001, /*num_bits:*/ 63_999_979,
);
bencher.iter(|| {
deduper.reset();
deduper.maybe_reset(&mut rng, /*reset_cycle:*/ &Duration::from_millis(0));
});
}

217
perf/src/deduper.rs
View File

@ -3,82 +3,71 @@
use {
crate::packet::{Packet, PacketBatch},
ahash::AHasher,
rand::{thread_rng, Rng},
solana_sdk::saturating_add_assign,
rand::Rng,
std::{
convert::TryFrom,
hash::Hasher,
sync::atomic::{AtomicBool, AtomicU64, Ordering},
hash::{Hash, Hasher},
iter::repeat_with,
sync::atomic::{AtomicU64, Ordering},
time::{Duration, Instant},
},
};
pub struct Deduper {
filter: Vec<AtomicU64>,
seed: (u128, u128),
age: Instant,
max_age: Duration,
pub saturated: AtomicBool,
pub struct Deduper<const K: usize> {
num_bits: u64,
bits: Vec<AtomicU64>,
seeds: [(u128, u128); K],
clock: Instant,
// Maximum number of one bits before the false positive
// rate exceeds the specified threshold.
capacity: u64,
popcount: AtomicU64, // Number of one bits in self.bits.
}
impl Deduper {
pub fn new(size: u32, max_age: Duration) -> Self {
let mut filter: Vec<AtomicU64> = Vec::with_capacity(size as usize);
filter.resize_with(size as usize, Default::default);
let seed = thread_rng().gen();
impl<const K: usize> Deduper<K> {
pub fn new<R: Rng>(rng: &mut R, false_positive_rate: f64, num_bits: u64) -> Self {
assert!(0.0 < false_positive_rate && false_positive_rate < 1.0);
let size = usize::try_from(num_bits.checked_add(63).unwrap() / 64).unwrap();
let capacity = num_bits as f64 * false_positive_rate.powf(1f64 / K as f64);
Self {
filter,
seed,
age: Instant::now(),
max_age,
saturated: AtomicBool::new(false),
num_bits,
seeds: std::array::from_fn(|_| rng.gen()),
clock: Instant::now(),
bits: repeat_with(AtomicU64::default).take(size).collect(),
capacity: capacity as u64,
popcount: AtomicU64::default(),
}
}
pub fn reset(&mut self) {
let now = Instant::now();
//this should reset every 500k unique packets per 1m sized deduper
//false positive rate is 1/1000 at that point
let saturated = self.saturated.load(Ordering::Relaxed);
if saturated || now.duration_since(self.age) > self.max_age {
let len = self.filter.len();
self.filter.clear();
self.filter.resize_with(len, AtomicU64::default);
self.seed = thread_rng().gen();
self.age = now;
self.saturated.store(false, Ordering::Relaxed);
pub fn maybe_reset<R: Rng>(&mut self, rng: &mut R, reset_cycle: &Duration) {
let popcount = self.popcount.load(Ordering::Relaxed);
if popcount >= self.capacity || &self.clock.elapsed() >= reset_cycle {
self.seeds = std::array::from_fn(|_| rng.gen());
self.clock = Instant::now();
self.bits.fill_with(AtomicU64::default);
self.popcount = AtomicU64::default();
}
}
/// Compute hash from packet data, returns (hash, bin_pos).
fn compute_hash(&self, packet: &Packet) -> (u64, usize) {
let mut hasher = AHasher::new_with_keys(self.seed.0, self.seed.1);
hasher.write(packet.data(..).unwrap_or_default());
let h = hasher.finish();
let len = self.filter.len();
let pos = (usize::try_from(h).unwrap()).wrapping_rem(len);
(h, pos)
}
// Deduplicates packets and returns 1 if packet is to be discarded. Else, 0.
fn dedup_packet(&self, packet: &mut Packet) -> u64 {
// If this packet was already marked as discard, drop it
if packet.meta().discard() {
return 1;
// Returns true if the packet is duplicate.
#[must_use]
#[allow(clippy::integer_arithmetic)]
fn dedup_packet(&self, packet: &Packet) -> bool {
// Should not dedup packet if already discarded.
debug_assert!(!packet.meta().discard());
let mut out = true;
for seed in self.seeds {
let mut hasher = AHasher::new_with_keys(seed.0, seed.1);
packet.data(..).unwrap_or_default().hash(&mut hasher);
let hash: u64 = hasher.finish() % self.num_bits;
let index = (hash >> 6) as usize;
let mask: u64 = 1u64 << (hash & 63);
let old = self.bits[index].fetch_or(mask, Ordering::Relaxed);
if old & mask == 0u64 {
self.popcount.fetch_add(1, Ordering::Relaxed);
out = false;
}
}
let (hash, pos) = self.compute_hash(packet);
// saturate each position with or
let prev = self.filter[pos].fetch_or(hash, Ordering::Relaxed);
if prev == u64::MAX {
self.saturated.store(true, Ordering::Relaxed);
//reset this value
self.filter[pos].store(hash, Ordering::Relaxed);
}
if hash == prev & hash {
packet.meta_mut().set_discard(true);
return 1;
}
0
out
}
pub fn dedup_packets_and_count_discards(
@ -86,18 +75,21 @@ impl Deduper {
batches: &mut [PacketBatch],
mut process_received_packet: impl FnMut(&mut Packet, bool, bool),
) -> u64 {
let mut num_removed: u64 = 0;
batches.iter_mut().for_each(|batch| {
batch.iter_mut().for_each(|p| {
let removed_before_sigverify = p.meta().discard();
let is_duplicate = self.dedup_packet(p);
if is_duplicate == 1 {
saturating_add_assign!(num_removed, 1);
batches
.iter_mut()
.flat_map(PacketBatch::iter_mut)
.map(|packet| {
if packet.meta().discard() {
process_received_packet(packet, true, false);
} else if self.dedup_packet(packet) {
packet.meta_mut().set_discard(true);
process_received_packet(packet, false, true);
} else {
process_received_packet(packet, false, false);
}
process_received_packet(p, removed_before_sigverify, is_duplicate == 1);
u64::from(packet.meta().discard())
})
});
num_removed
.sum()
}
}
@ -107,6 +99,10 @@ mod tests {
use {
super::*,
crate::{packet::to_packet_batches, sigverify, test_tx::test_tx},
rand::SeedableRng,
rand_chacha::ChaChaRng,
solana_sdk::packet::{Meta, PACKET_DATA_SIZE},
test_case::test_case,
};
#[test]
@ -116,7 +112,10 @@ mod tests {
let mut batches =
to_packet_batches(&std::iter::repeat(tx).take(1024).collect::<Vec<_>>(), 128);
let packet_count = sigverify::count_packets_in_batches(&batches);
let filter = Deduper::new(1_000_000, Duration::from_millis(0));
let mut rng = rand::thread_rng();
let filter = Deduper::<2>::new(
&mut rng, /*false_positive_rate:*/ 0.001, /*num_bits:*/ 63_999_979,
);
let mut num_deduped = 0;
let discard = filter.dedup_packets_and_count_discards(
&mut batches,
@ -130,13 +129,16 @@ mod tests {
#[test]
fn test_dedup_diff() {
let mut filter = Deduper::new(1_000_000, Duration::from_millis(0));
let mut rng = rand::thread_rng();
let mut filter = Deduper::<2>::new(
&mut rng, /*false_positive_rate:*/ 0.001, /*num_bits:*/ 63_999_979,
);
let mut batches = to_packet_batches(&(0..1024).map(|_| test_tx()).collect::<Vec<_>>(), 128);
let discard = filter.dedup_packets_and_count_discards(&mut batches, |_, _, _| ()) as usize;
// because dedup uses a threadpool, there maybe up to N threads of txs that go through
assert_eq!(discard, 0);
filter.reset();
for i in filter.filter {
filter.maybe_reset(&mut rng, /*reset_cycle:*/ &Duration::from_millis(0));
for i in filter.bits {
assert_eq!(i.load(Ordering::Relaxed), 0);
}
}
@ -144,24 +146,30 @@ mod tests {
#[test]
#[ignore]
fn test_dedup_saturated() {
let filter = Deduper::new(1_000_000, Duration::from_millis(0));
let mut rng = rand::thread_rng();
let filter = Deduper::<2>::new(
&mut rng, /*false_positive_rate:*/ 0.001, /*num_bits:*/ 63_999_979,
);
let mut discard = 0;
assert!(!filter.saturated.load(Ordering::Relaxed));
assert!(filter.popcount.load(Ordering::Relaxed) < filter.capacity);
for i in 0..1000 {
let mut batches =
to_packet_batches(&(0..1000).map(|_| test_tx()).collect::<Vec<_>>(), 128);
discard += filter.dedup_packets_and_count_discards(&mut batches, |_, _, _| ()) as usize;
trace!("{} {}", i, discard);
if filter.saturated.load(Ordering::Relaxed) {
if filter.popcount.load(Ordering::Relaxed) >= filter.capacity {
break;
}
}
assert!(filter.saturated.load(Ordering::Relaxed));
assert!(filter.popcount.load(Ordering::Relaxed) >= filter.capacity);
}
#[test]
fn test_dedup_false_positive() {
let filter = Deduper::new(1_000_000, Duration::from_millis(0));
let mut rng = rand::thread_rng();
let filter = Deduper::<2>::new(
&mut rng, /*false_positive_rate:*/ 0.001, /*num_bits:*/ 63_999_979,
);
let mut discard = 0;
for i in 0..10 {
let mut batches =
@ -172,4 +180,53 @@ mod tests {
//allow for 1 false positive even if extremely unlikely
assert!(discard < 2);
}
#[test_case(63_999_979, 0.001, 2_023_857)]
#[test_case(622_401_961, 0.001, 19_682_078)]
#[test_case(622_401_979, 0.001, 19_682_078)]
#[test_case(629_145_593, 0.001, 19_895_330)]
#[test_case(632_455_543, 0.001, 20_000_000)]
#[test_case(637_534_199, 0.001, 20_160_601)]
#[test_case(622_401_961, 0.0001, 6_224_019)]
#[test_case(622_401_979, 0.0001, 6_224_019)]
#[test_case(629_145_593, 0.0001, 6_291_455)]
#[test_case(632_455_543, 0.0001, 6_324_555)]
#[test_case(637_534_199, 0.0001, 6_375_341)]
fn test_dedup_capacity(num_bits: u64, false_positive_rate: f64, capacity: u64) {
let mut rng = rand::thread_rng();
let deduper = Deduper::<2>::new(&mut rng, false_positive_rate, num_bits);
assert_eq!(deduper.capacity, capacity);
}
#[test_case([0xf9; 32], 3_199_997, 101_192, 51_414, 70, 101_125)]
#[test_case([0xdc; 32], 3_200_003, 101_192, 51_414, 71, 101_132)]
#[test_case([0xa5; 32], 6_399_971, 202_384, 102_828, 127, 202_157)]
#[test_case([0xdb; 32], 6_400_013, 202_386, 102_828, 145, 202_277)]
#[test_case([0xcd; 32], 12_799_987, 404_771, 205_655, 289, 404_434)]
#[test_case([0xc3; 32], 12_800_009, 404_771, 205_656, 309, 404_278)]
fn test_dedup_seeded(
seed: [u8; 32],
num_bits: u64,
capacity: u64,
num_packets: usize,
num_dups: usize,
popcount: u64,
) {
let mut rng = ChaChaRng::from_seed(seed);
let deduper = Deduper::<2>::new(&mut rng, /*false_positive_rate:*/ 0.001, num_bits);
assert_eq!(deduper.capacity, capacity);
let mut packet = Packet::new([0u8; PACKET_DATA_SIZE], Meta::default());
let mut dup_count = 0usize;
for _ in 0..num_packets {
let size = rng.gen_range(0, PACKET_DATA_SIZE);
packet.meta_mut().size = size;
rng.fill(&mut packet.buffer_mut()[0..size]);
if deduper.dedup_packet(&packet) {
dup_count += 1;
}
assert!(deduper.dedup_packet(&packet));
}
assert_eq!(dup_count, num_dups);
assert_eq!(deduper.popcount.load(Ordering::Relaxed), popcount);
}
}