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refactor: memory management (#13636)
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| // Copyright 2023 RisingWave Labs | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
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| use std::sync::Arc; | ||
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| use risingwave_common::util::epoch::Epoch; | ||
| use risingwave_jni_core::jvm_runtime::load_jvm_memory_stats; | ||
| use risingwave_stream::executor::monitor::StreamingMetrics; | ||
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| /// Internal state of [`LruWatermarkController`] that saves the state in previous tick. | ||
| struct State { | ||
| pub used_memory_bytes: usize, | ||
| pub lru_watermark_step: u64, | ||
| pub lru_watermark_time_ms: u64, | ||
| } | ||
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| impl Default for State { | ||
| fn default() -> Self { | ||
| let physical_now = Epoch::physical_now(); | ||
| Self { | ||
| used_memory_bytes: 0, | ||
| lru_watermark_step: 0, | ||
| lru_watermark_time_ms: physical_now, | ||
| } | ||
| } | ||
| } | ||
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| /// `LruWatermarkController` controls LRU Watermark (epoch) according to actual memory usage statistics | ||
| /// collected from Jemalloc and JVM. | ||
| /// | ||
| /// Basically, it works as a negative feedback loop: collect memory statistics, and then set the LRU watarmarking | ||
| /// according to maintain the memory usage in a proper level. | ||
| /// | ||
| /// ```text | ||
| /// ┌───────────────────┐ ┌───────────────────┐ | ||
| /// │ INPUT │ │ OUTPUT │ | ||
| /// ┌───► (observe) ├───────►│ (control) ├───┐ | ||
| /// │ │ Memory Statistics │ │ New LRU Watermark │ │ | ||
| /// │ └───────────────────┘ └───────────────────┘ │ | ||
| /// │ │ | ||
| /// └────────────────────────────────────────────────────────┘ | ||
| /// ``` | ||
| /// | ||
| /// Check the function [`Self::tick()`] to see the control policy. | ||
| pub struct LruWatermarkController { | ||
| metrics: Arc<StreamingMetrics>, | ||
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| threshold_stable: usize, | ||
| threshold_graceful: usize, | ||
| threshold_aggressive: usize, | ||
|
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| /// The state from previous tick | ||
| state: State, | ||
| } | ||
|
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| impl LruWatermarkController { | ||
| // TODO(eric): make them configurable | ||
| const THRESHOLD_AGGRESSIVE: f64 = 0.9; | ||
| const THRESHOLD_GRACEFUL: f64 = 0.8; | ||
| const THRESHOLD_STABLE: f64 = 0.7; | ||
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| pub fn new(total_memory: usize, metrics: Arc<StreamingMetrics>) -> Self { | ||
| let threshold_stable = (total_memory as f64 * Self::THRESHOLD_STABLE) as usize; | ||
| let threshold_graceful = (total_memory as f64 * Self::THRESHOLD_GRACEFUL) as usize; | ||
| let threshold_aggressive = (total_memory as f64 * Self::THRESHOLD_AGGRESSIVE) as usize; | ||
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| Self { | ||
| metrics, | ||
| threshold_stable, | ||
| threshold_graceful, | ||
| threshold_aggressive, | ||
| state: State::default(), | ||
| } | ||
| } | ||
| } | ||
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| impl std::fmt::Debug for LruWatermarkController { | ||
| fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { | ||
| f.debug_struct("LruWatermarkController") | ||
| .field("threshold_stable", &self.threshold_stable) | ||
| .field("threshold_graceful", &self.threshold_graceful) | ||
| .field("threshold_aggressive", &self.threshold_aggressive) | ||
| .finish() | ||
| } | ||
| } | ||
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| /// Get memory statistics from Jemalloc | ||
| /// | ||
| /// - `stats.allocated`: Total number of bytes allocated by the application. | ||
| /// - `stats.active`: Total number of bytes in active pages allocated by the application. This is a multiple of the page size, and greater than or equal to `stats.allocated`. This does not include `stats.arenas.<i>.pdirty`, `stats.arenas.<i>.pmuzzy`, nor pages entirely devoted to allocator metadata. | ||
| /// | ||
| /// Reference: <https://jemalloc.net/jemalloc.3.html> | ||
| fn jemalloc_memory_stats() -> (usize, usize) { | ||
| if let Err(e) = tikv_jemalloc_ctl::epoch::advance() { | ||
| tracing::warn!("Jemalloc epoch advance failed! {:?}", e); | ||
| } | ||
| let allocated = tikv_jemalloc_ctl::stats::allocated::read().unwrap(); | ||
| let active = tikv_jemalloc_ctl::stats::active::read().unwrap(); | ||
| (allocated, active) | ||
| } | ||
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| impl LruWatermarkController { | ||
| pub fn tick(&mut self, interval_ms: u32) -> Epoch { | ||
| // NOTE: Be careful! The meaning of `allocated` and `active` differ in JeMalloc and JVM | ||
| let (jemalloc_allocated_bytes, jemalloc_active_bytes) = jemalloc_memory_stats(); | ||
| let (jvm_allocated_bytes, jvm_active_bytes) = load_jvm_memory_stats(); | ||
|
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| let cur_used_memory_bytes = jemalloc_active_bytes + jvm_allocated_bytes; | ||
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| let last_step = self.state.lru_watermark_step; | ||
| let last_used_memory_bytes = self.state.used_memory_bytes; | ||
|
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| // The watermark calculation works in the following way: | ||
| // | ||
| // 1. When the streaming memory usage is below the graceful threshold, we do not evict | ||
| // any caches, and simply reset the step to 0. | ||
| // | ||
| // 2. When the memory usage is between the graceful and aggressive threshold: | ||
| // - If the last eviction memory usage decreases after last eviction, we set the eviction step | ||
| // to 1. | ||
| // - Otherwise, we set the step to last_step + 1. | ||
| // | ||
| // 3. When the memory usage exceeds the aggressive threshold: | ||
| // - If the memory usage decreases after the last eviction, we set the eviction step to | ||
| // last_step. | ||
| // - Otherwise, we set the step to last_step * 2. | ||
| let mut step = if cur_used_memory_bytes < self.threshold_stable { | ||
| // Do not evict if the memory usage is lower than `threshold_stable` | ||
| 0 | ||
| } else if cur_used_memory_bytes < self.threshold_graceful { | ||
| // Evict in equal speed of time before `threshold_graceful` | ||
| 1 | ||
| } else if cur_used_memory_bytes < self.threshold_aggressive { | ||
| // Gracefully evict | ||
| if last_used_memory_bytes > cur_used_memory_bytes { | ||
| 1 | ||
| } else { | ||
| last_step + 1 | ||
| } | ||
| } else if last_used_memory_bytes < cur_used_memory_bytes { | ||
| // Aggressively evict | ||
| if last_step == 0 { | ||
| 2 | ||
| } else { | ||
| last_step * 2 | ||
| } | ||
| } else { | ||
| last_step | ||
| }; | ||
|
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| let physical_now = Epoch::physical_now(); | ||
| let watermark_time_ms = | ||
| if (physical_now - self.state.lru_watermark_time_ms) / (interval_ms as u64) < step { | ||
| // We do not increase the step and watermark here to prevent a too-advanced watermark. The | ||
| // original condition is `prev_watermark_time_ms + interval_ms * step > now`. | ||
| step = last_step; | ||
| physical_now | ||
| } else { | ||
| // Increase by (steps * interval) | ||
| self.state.lru_watermark_time_ms + (interval_ms as u64 * step) | ||
| }; | ||
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| self.state = State { | ||
| used_memory_bytes: cur_used_memory_bytes, | ||
| lru_watermark_step: step, | ||
| lru_watermark_time_ms: watermark_time_ms, | ||
| }; | ||
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| self.metrics | ||
| .lru_current_watermark_time_ms | ||
| .set(watermark_time_ms as i64); | ||
| self.metrics.lru_physical_now_ms.set(physical_now as i64); | ||
| self.metrics.lru_watermark_step.set(step as i64); | ||
| self.metrics | ||
| .jemalloc_allocated_bytes | ||
| .set(jemalloc_allocated_bytes as i64); | ||
| self.metrics | ||
| .jemalloc_active_bytes | ||
| .set(jemalloc_active_bytes as i64); | ||
| self.metrics | ||
| .jvm_allocated_bytes | ||
| .set(jvm_allocated_bytes as i64); | ||
| self.metrics.jvm_active_bytes.set(jvm_active_bytes as i64); | ||
|
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| Epoch::from_physical_time(watermark_time_ms) | ||
| } | ||
| } |
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