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replay stage feed back program cost (#17731)

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* replay stage feeds back realtime per-program execution cost to cost model;

* program cost execution table is initialized into empty table, no longer populated with hardcoded numbers;

* changed cost unit to microsecond, using value collected from mainnet;

* add ExecuteCostTable with fixed capacity for security concern, when its limit is reached, programs with old age AND less occurrence will be pushed out to make room for new programs.
This commit is contained in:
Tao Zhu
2021-06-09 17:10:59 -05:00
committed by GitHub
parent 050bb5446d
commit ae27fcbcda
11 changed files with 542 additions and 174 deletions
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277
core/src/execute_cost_table.rs Normal file
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/// ExecuteCostTable is aggregated by Cost Model, it keeps each program's
/// average cost in its HashMap, with fixed capacity to avoid from growing
/// unchecked.
/// When its capacity limit is reached, it prunes old and less-used programs
/// to make room for new ones.
use log::*;
use solana_sdk::pubkey::Pubkey;
use std::{collections::HashMap, time::SystemTime};
// prune is rather expensive op, free up bulk space in each operation
// would be more efficient. PRUNE_RATIO defines the after prune table
// size will be original_size * PRUNE_RATIO.
const PRUNE_RATIO: f64 = 0.75;
// with 50_000 TPS as norm, weights occurrences '100' per microsec
const OCCURRENCES_WEIGHT: i64 = 100;
const DEFAULT_CAPACITY: usize = 1024;
#[derive(Debug)]
pub struct ExecuteCostTable {
capacity: usize,
table: HashMap<Pubkey, u64>,
occurrences: HashMap<Pubkey, (usize, SystemTime)>,
}
impl Default for ExecuteCostTable {
fn default() -> Self {
ExecuteCostTable::new(DEFAULT_CAPACITY)
}
}
impl ExecuteCostTable {
pub fn new(cap: usize) -> Self {
Self {
capacity: cap,
table: HashMap::new(),
occurrences: HashMap::new(),
}
}
pub fn get_cost_table(&self) -> &HashMap<Pubkey, u64> {
&self.table
}
pub fn get_count(&self) -> usize {
self.table.len()
}
// instead of assigning unknown program with a configured/hard-coded cost
// use average or mode function to make a educated guess.
pub fn get_average(&self) -> u64 {
if self.table.is_empty() {
0
} else {
self.table.iter().map(|(_, value)| value).sum::<u64>() / self.get_count() as u64
}
}
pub fn get_mode(&self) -> u64 {
if self.occurrences.is_empty() {
0
} else {
let key = self
.occurrences
.iter()
.max_by_key(|&(_, count)| count)
.map(|(key, _)| key)
.expect("cannot find mode from cost table");
*self.table.get(&key).unwrap()
}
}
// returns None if program doesn't exist in table. In this case,
// client is advised to call `get_average()` or `get_mode()` to
// assign a 'default' value for new program.
pub fn get_cost(&self, key: &Pubkey) -> Option<&u64> {
self.table.get(&key)
}
pub fn upsert(&mut self, key: &Pubkey, value: &u64) {
let need_to_add = self.table.get(&key).is_none();
let current_size = self.get_count();
if current_size == self.capacity && need_to_add {
self.prune_to(&((current_size as f64 * PRUNE_RATIO) as usize));
}
let program_cost = self.table.entry(*key).or_insert(*value);
*program_cost = (*program_cost + *value) / 2;
let (count, timestamp) = self
.occurrences
.entry(*key)
.or_insert((0, SystemTime::now()));
*count += 1;
*timestamp = SystemTime::now();
}
// prune the old programs so the table contains `new_size` of records,
// where `old` is defined as weighted age, which is negatively correlated
// with program's age and
// positively correlated with how frequently the program
// is executed (eg. occurrence),
fn prune_to(&mut self, new_size: &usize) {
debug!(
"prune cost table, current size {}, new size {}",
self.get_count(),
new_size
);
if *new_size == self.get_count() {
return;
}
if *new_size == 0 {
self.table.clear();
self.occurrences.clear();
return;
}
let now = SystemTime::now();
let mut sorted_by_weighted_age: Vec<_> = self
.occurrences
.iter()
.map(|(key, (count, timestamp))| {
let age = now.duration_since(*timestamp).unwrap().as_micros();
let weighted_age = *count as i64 * OCCURRENCES_WEIGHT + -(age as i64);
(weighted_age, *key)
})
.collect();
sorted_by_weighted_age.sort_by(|x, y| x.0.partial_cmp(&y.0).unwrap());
for i in sorted_by_weighted_age.iter() {
self.table.remove(&i.1);
self.occurrences.remove(&i.1);
if *new_size == self.get_count() {
break;
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_execute_cost_table_prune_simple_table() {
solana_logger::setup();
let capacity: usize = 3;
let mut testee = ExecuteCostTable::new(capacity);
let key1 = Pubkey::new_unique();
let key2 = Pubkey::new_unique();
let key3 = Pubkey::new_unique();
testee.upsert(&key1, &1);
testee.upsert(&key2, &2);
testee.upsert(&key3, &3);
testee.prune_to(&(capacity - 1));
// the oldest, key1, should be pruned
assert!(testee.get_cost(&key1).is_none());
assert!(testee.get_cost(&key2).is_some());
assert!(testee.get_cost(&key2).is_some());
}
#[test]
fn test_execute_cost_table_prune_weighted_table() {
solana_logger::setup();
let capacity: usize = 3;
let mut testee = ExecuteCostTable::new(capacity);
let key1 = Pubkey::new_unique();
let key2 = Pubkey::new_unique();
let key3 = Pubkey::new_unique();
testee.upsert(&key1, &1);
testee.upsert(&key1, &1);
testee.upsert(&key2, &2);
testee.upsert(&key3, &3);
testee.prune_to(&(capacity - 1));
// the oldest, key1, has 2 counts; 2nd oldest Key2 has 1 count;
// expect key2 to be pruned.
assert!(testee.get_cost(&key1).is_some());
assert!(testee.get_cost(&key2).is_none());
assert!(testee.get_cost(&key3).is_some());
}
#[test]
fn test_execute_cost_table_upsert_within_capacity() {
solana_logger::setup();
let mut testee = ExecuteCostTable::default();
let key1 = Pubkey::new_unique();
let key2 = Pubkey::new_unique();
let cost1: u64 = 100;
let cost2: u64 = 110;
// query empty table
assert!(testee.get_cost(&key1).is_none());
// insert one record
testee.upsert(&key1, &cost1);
assert_eq!(1, testee.get_count());
assert_eq!(cost1, testee.get_average());
assert_eq!(cost1, testee.get_mode());
assert_eq!(&cost1, testee.get_cost(&key1).unwrap());
// insert 2nd record
testee.upsert(&key2, &cost2);
assert_eq!(2, testee.get_count());
assert_eq!((cost1 + cost2) / 2_u64, testee.get_average());
assert_eq!(cost2, testee.get_mode());
assert_eq!(&cost1, testee.get_cost(&key1).unwrap());
assert_eq!(&cost2, testee.get_cost(&key2).unwrap());
// update 1st record
testee.upsert(&key1, &cost2);
assert_eq!(2, testee.get_count());
assert_eq!(((cost1 + cost2) / 2 + cost2) / 2, testee.get_average());
assert_eq!((cost1 + cost2) / 2, testee.get_mode());
assert_eq!(&((cost1 + cost2) / 2), testee.get_cost(&key1).unwrap());
assert_eq!(&cost2, testee.get_cost(&key2).unwrap());
}
#[test]
fn test_execute_cost_table_upsert_exceeds_capacity() {
solana_logger::setup();
let capacity: usize = 2;
let mut testee = ExecuteCostTable::new(capacity);
let key1 = Pubkey::new_unique();
let key2 = Pubkey::new_unique();
let key3 = Pubkey::new_unique();
let key4 = Pubkey::new_unique();
let cost1: u64 = 100;
let cost2: u64 = 110;
let cost3: u64 = 120;
let cost4: u64 = 130;
// insert one record
testee.upsert(&key1, &cost1);
assert_eq!(1, testee.get_count());
assert_eq!(&cost1, testee.get_cost(&key1).unwrap());
// insert 2nd record
testee.upsert(&key2, &cost2);
assert_eq!(2, testee.get_count());
assert_eq!(&cost1, testee.get_cost(&key1).unwrap());
assert_eq!(&cost2, testee.get_cost(&key2).unwrap());
// insert 3rd record, pushes out the oldest (eg 1st) record
testee.upsert(&key3, &cost3);
assert_eq!(2, testee.get_count());
assert_eq!((cost2 + cost3) / 2_u64, testee.get_average());
assert_eq!(cost3, testee.get_mode());
assert!(testee.get_cost(&key1).is_none());
assert_eq!(&cost2, testee.get_cost(&key2).unwrap());
assert_eq!(&cost3, testee.get_cost(&key3).unwrap());
// update 2nd record, so the 3rd becomes the oldest
// add 4th record, pushes out 3rd key
testee.upsert(&key2, &cost1);
testee.upsert(&key4, &cost4);
assert_eq!(((cost1 + cost2) / 2 + cost4) / 2_u64, testee.get_average());
assert_eq!((cost1 + cost2) / 2, testee.get_mode());
assert_eq!(2, testee.get_count());
assert!(testee.get_cost(&key1).is_none());
assert_eq!(&((cost1 + cost2) / 2), testee.get_cost(&key2).unwrap());
assert!(testee.get_cost(&key3).is_none());
assert_eq!(&cost4, testee.get_cost(&key4).unwrap());
}
}