solana_perf/
deduper.rs

1//! Utility to deduplicate baches of incoming network packets.
2
3use {
4    crate::packet::PacketBatch,
5    ahash::RandomState,
6    rand::Rng,
7    std::{
8        hash::Hash,
9        iter::repeat_with,
10        marker::PhantomData,
11        sync::atomic::{AtomicU64, Ordering},
12        time::{Duration, Instant},
13    },
14};
15
16pub struct Deduper<const K: usize, T: ?Sized> {
17    num_bits: u64,
18    bits: Vec<AtomicU64>,
19    state: [RandomState; K],
20    clock: Instant,
21    popcount: AtomicU64, // Number of one bits in self.bits.
22    _phantom: PhantomData<T>,
23}
24
25impl<const K: usize, T: ?Sized + Hash> Deduper<K, T> {
26    pub fn new<R: Rng>(rng: &mut R, num_bits: u64) -> Self {
27        let size = num_bits.checked_add(63).unwrap() / 64;
28        let size = usize::try_from(size).unwrap();
29        Self {
30            num_bits,
31            state: std::array::from_fn(|_| new_random_state(rng)),
32            clock: Instant::now(),
33            bits: repeat_with(AtomicU64::default).take(size).collect(),
34            popcount: AtomicU64::default(),
35            _phantom: PhantomData::<T>,
36        }
37    }
38
39    fn false_positive_rate(&self) -> f64 {
40        let popcount = self.popcount.load(Ordering::Relaxed);
41        let ones_ratio = popcount.min(self.num_bits) as f64 / self.num_bits as f64;
42        ones_ratio.powi(K as i32)
43    }
44
45    /// Resets the Deduper if either it is older than the reset_cycle or it is
46    /// saturated enough that false positive rate exceeds specified threshold.
47    /// Returns true if the deduper was saturated.
48    pub fn maybe_reset<R: Rng>(
49        &mut self,
50        rng: &mut R,
51        false_positive_rate: f64,
52        reset_cycle: Duration,
53    ) -> bool {
54        assert!(0.0 < false_positive_rate && false_positive_rate < 1.0);
55        let saturated = self.false_positive_rate() >= false_positive_rate;
56        if saturated || self.clock.elapsed() >= reset_cycle {
57            self.state = std::array::from_fn(|_| new_random_state(rng));
58            self.clock = Instant::now();
59            self.bits.fill_with(AtomicU64::default);
60            self.popcount = AtomicU64::default();
61        }
62        saturated
63    }
64
65    // Returns true if the data is duplicate.
66    #[must_use]
67    #[allow(clippy::arithmetic_side_effects)]
68    pub fn dedup(&self, data: &T) -> bool {
69        let mut out = true;
70        for random_state in &self.state {
71            let hash: u64 = random_state.hash_one(data) % self.num_bits;
72            let index = (hash >> 6) as usize;
73            let mask: u64 = 1u64 << (hash & 63);
74            let old = self.bits[index].fetch_or(mask, Ordering::Relaxed);
75            if old & mask == 0u64 {
76                self.popcount.fetch_add(1, Ordering::Relaxed);
77                out = false;
78            }
79        }
80        out
81    }
82}
83
84fn new_random_state<R: Rng>(rng: &mut R) -> RandomState {
85    RandomState::with_seeds(rng.gen(), rng.gen(), rng.gen(), rng.gen())
86}
87
88pub fn dedup_packets_and_count_discards<const K: usize>(
89    deduper: &Deduper<K, [u8]>,
90    batches: &mut [PacketBatch],
91) -> u64 {
92    batches
93        .iter_mut()
94        .flat_map(PacketBatch::iter_mut)
95        .map(|packet| {
96            if !packet.meta().discard()
97                && packet
98                    .data(..)
99                    .map(|data| deduper.dedup(data))
100                    .unwrap_or(true)
101            {
102                packet.meta_mut().set_discard(true);
103            }
104            u64::from(packet.meta().discard())
105        })
106        .sum()
107}
108
109#[cfg(test)]
110#[allow(clippy::arithmetic_side_effects)]
111mod tests {
112    use {
113        super::*,
114        crate::{
115            packet::{to_packet_batches, Packet},
116            sigverify,
117            test_tx::test_tx,
118        },
119        rand::SeedableRng,
120        rand_chacha::ChaChaRng,
121        solana_packet::{Meta, PACKET_DATA_SIZE},
122        test_case::test_case,
123    };
124
125    #[test]
126    fn test_dedup_same() {
127        let tx = test_tx();
128
129        let mut batches =
130            to_packet_batches(&std::iter::repeat(tx).take(1024).collect::<Vec<_>>(), 128);
131        let packet_count = sigverify::count_packets_in_batches(&batches);
132        let mut rng = rand::thread_rng();
133        let filter = Deduper::<2, [u8]>::new(&mut rng, /*num_bits:*/ 63_999_979);
134        let discard = dedup_packets_and_count_discards(&filter, &mut batches) as usize;
135        assert_eq!(packet_count, discard + 1);
136    }
137
138    #[test]
139    fn test_dedup_diff() {
140        let mut rng = rand::thread_rng();
141        let mut filter = Deduper::<2, [u8]>::new(&mut rng, /*num_bits:*/ 63_999_979);
142        let mut batches = to_packet_batches(&(0..1024).map(|_| test_tx()).collect::<Vec<_>>(), 128);
143        let discard = dedup_packets_and_count_discards(&filter, &mut batches) as usize;
144        // because dedup uses a threadpool, there maybe up to N threads of txs that go through
145        assert_eq!(discard, 0);
146        assert!(!filter.maybe_reset(
147            &mut rng,
148            0.001,                    // false_positive_rate
149            Duration::from_millis(0), // reset_cycle
150        ));
151        for i in filter.bits {
152            assert_eq!(i.load(Ordering::Relaxed), 0);
153        }
154    }
155
156    fn get_capacity<const K: usize>(num_bits: u64, false_positive_rate: f64) -> u64 {
157        (num_bits as f64 * false_positive_rate.powf(1f64 / K as f64)) as u64
158    }
159
160    #[test]
161    #[ignore]
162    fn test_dedup_saturated() {
163        const NUM_BITS: u64 = 63_999_979;
164        const FALSE_POSITIVE_RATE: f64 = 0.001;
165        let mut rng = rand::thread_rng();
166        let mut filter = Deduper::<2, [u8]>::new(&mut rng, NUM_BITS);
167        let capacity = get_capacity::<2>(NUM_BITS, FALSE_POSITIVE_RATE);
168        let mut discard = 0;
169        assert!(filter.popcount.load(Ordering::Relaxed) < capacity);
170        for i in 0..1000 {
171            let mut batches =
172                to_packet_batches(&(0..1000).map(|_| test_tx()).collect::<Vec<_>>(), 128);
173            discard += dedup_packets_and_count_discards(&filter, &mut batches) as usize;
174            trace!("{} {}", i, discard);
175            if filter.popcount.load(Ordering::Relaxed) > capacity {
176                break;
177            }
178        }
179        assert!(filter.popcount.load(Ordering::Relaxed) > capacity);
180        assert!(filter.false_positive_rate() >= FALSE_POSITIVE_RATE);
181        assert!(filter.maybe_reset(
182            &mut rng,
183            FALSE_POSITIVE_RATE,
184            Duration::from_millis(0), // reset_cycle
185        ));
186    }
187
188    #[test]
189    fn test_dedup_false_positive() {
190        let mut rng = rand::thread_rng();
191        let filter = Deduper::<2, [u8]>::new(&mut rng, /*num_bits:*/ 63_999_979);
192        let mut discard = 0;
193        for i in 0..10 {
194            let mut batches =
195                to_packet_batches(&(0..1024).map(|_| test_tx()).collect::<Vec<_>>(), 128);
196            discard += dedup_packets_and_count_discards(&filter, &mut batches) as usize;
197            debug!("false positive rate: {}/{}", discard, i * 1024);
198        }
199        //allow for 1 false positive even if extremely unlikely
200        assert!(discard < 2);
201    }
202
203    #[test_case(63_999_979, 0.001, 2_023_857)]
204    #[test_case(622_401_961, 0.001, 19_682_078)]
205    #[test_case(622_401_979, 0.001, 19_682_078)]
206    #[test_case(629_145_593, 0.001, 19_895_330)]
207    #[test_case(632_455_543, 0.001, 20_000_000)]
208    #[test_case(637_534_199, 0.001, 20_160_601)]
209    #[test_case(622_401_961, 0.0001, 6_224_019)]
210    #[test_case(622_401_979, 0.0001, 6_224_019)]
211    #[test_case(629_145_593, 0.0001, 6_291_455)]
212    #[test_case(632_455_543, 0.0001, 6_324_555)]
213    #[test_case(637_534_199, 0.0001, 6_375_341)]
214    fn test_dedup_capacity(num_bits: u64, false_positive_rate: f64, capacity: u64) {
215        let mut rng = rand::thread_rng();
216        assert_eq!(get_capacity::<2>(num_bits, false_positive_rate), capacity);
217        let mut deduper = Deduper::<2, [u8]>::new(&mut rng, num_bits);
218        assert_eq!(deduper.false_positive_rate(), 0.0);
219        deduper.popcount.store(capacity, Ordering::Relaxed);
220        assert!(deduper.false_positive_rate() < false_positive_rate);
221        deduper.popcount.store(capacity + 1, Ordering::Relaxed);
222        assert!(deduper.false_positive_rate() >= false_positive_rate);
223        assert!(deduper.maybe_reset(
224            &mut rng,
225            false_positive_rate,
226            Duration::from_millis(0), // reset_cycle
227        ));
228    }
229
230    #[test_case([0xf9; 32],  3_199_997, 101_192,  51_414,  77, 101_083)]
231    #[test_case([0xdc; 32],  3_200_003, 101_192,  51_414,  64, 101_097)]
232    #[test_case([0xa5; 32],  6_399_971, 202_384, 102_828, 117, 202_257)]
233    #[test_case([0xdb; 32],  6_400_013, 202_386, 102_828, 135, 202_254)]
234    #[test_case([0xcd; 32], 12_799_987, 404_771, 205_655, 273, 404_521)]
235    #[test_case([0xc3; 32], 12_800_009, 404_771, 205_656, 283, 404_365)]
236    fn test_dedup_seeded(
237        seed: [u8; 32],
238        num_bits: u64,
239        capacity: u64,
240        num_packets: usize,
241        num_dups: usize,
242        popcount: u64,
243    ) {
244        const FALSE_POSITIVE_RATE: f64 = 0.001;
245        let mut rng = ChaChaRng::from_seed(seed);
246        let mut deduper = Deduper::<2, [u8]>::new(&mut rng, num_bits);
247        assert_eq!(get_capacity::<2>(num_bits, FALSE_POSITIVE_RATE), capacity);
248        let mut packet = Packet::new([0u8; PACKET_DATA_SIZE], Meta::default());
249        let mut dup_count = 0usize;
250        for _ in 0..num_packets {
251            let size = rng.gen_range(0..PACKET_DATA_SIZE);
252            packet.meta_mut().size = size;
253            rng.fill(&mut packet.buffer_mut()[0..size]);
254            if deduper.dedup(packet.data(..).unwrap()) {
255                dup_count += 1;
256            }
257            assert!(deduper.dedup(packet.data(..).unwrap()));
258        }
259        assert_eq!(dup_count, num_dups);
260        assert_eq!(deduper.popcount.load(Ordering::Relaxed), popcount);
261        assert!(deduper.false_positive_rate() < FALSE_POSITIVE_RATE);
262        assert!(!deduper.maybe_reset(
263            &mut rng,
264            FALSE_POSITIVE_RATE,
265            Duration::from_millis(0), // reset_cycle
266        ));
267    }
268}
solana_perf/deduper.rs

solana_perf/
deduper.rs
