[GitHub] [arrow-datafusion] xiaoyong-z commented on a diff in pull request #4522: Simplify MemoryManager

["xiaoyong-z (via GitHub)" <gi...@apache.org>]

xiaoyong-z commented on code in PR #4522:
URL: https://github.com/apache/arrow-datafusion/pull/4522#discussion_r1094187143


##########
datafusion/core/src/execution/memory_pool/pool.rs:
##########
@@ -0,0 +1,285 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+use crate::execution::memory_pool::{MemoryConsumer, MemoryPool, MemoryReservation};
+use datafusion_common::{DataFusionError, Result};
+use parking_lot::Mutex;
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+/// A [`MemoryPool`] that enforces no limit
+#[derive(Debug, Default)]
+pub struct UnboundedMemoryPool {
+    used: AtomicUsize,
+}
+
+impl MemoryPool for UnboundedMemoryPool {
+    fn grow(&self, _reservation: &MemoryReservation, additional: usize) {
+        self.used.fetch_add(additional, Ordering::Relaxed);
+    }
+
+    fn shrink(&self, _reservation: &MemoryReservation, shrink: usize) {
+        self.used.fetch_sub(shrink, Ordering::Relaxed);
+    }
+
+    fn try_grow(&self, reservation: &MemoryReservation, additional: usize) -> Result<()> {
+        self.grow(reservation, additional);
+        Ok(())
+    }
+
+    fn reserved(&self) -> usize {
+        self.used.load(Ordering::Relaxed)
+    }
+}
+
+/// A [`MemoryPool`] that implements a greedy first-come first-serve limit
+#[derive(Debug)]
+pub struct GreedyMemoryPool {
+    pool_size: usize,
+    used: AtomicUsize,
+}
+
+impl GreedyMemoryPool {
+    /// Allocate up to `limit` bytes
+    pub fn new(pool_size: usize) -> Self {
+        Self {
+            pool_size,
+            used: AtomicUsize::new(0),
+        }
+    }
+}
+
+impl MemoryPool for GreedyMemoryPool {
+    fn grow(&self, _reservation: &MemoryReservation, additional: usize) {
+        self.used.fetch_add(additional, Ordering::Relaxed);
+    }
+
+    fn shrink(&self, _reservation: &MemoryReservation, shrink: usize) {
+        self.used.fetch_sub(shrink, Ordering::Relaxed);
+    }
+
+    fn try_grow(&self, reservation: &MemoryReservation, additional: usize) -> Result<()> {
+        self.used
+            .fetch_update(Ordering::Relaxed, Ordering::Relaxed, |used| {
+                let new_used = used + additional;
+                (new_used <= self.pool_size).then_some(new_used)
+            })
+            .map_err(|used| {
+                insufficient_capacity_err(reservation, additional, self.pool_size - used)
+            })?;
+        Ok(())
+    }
+
+    fn reserved(&self) -> usize {
+        self.used.load(Ordering::Relaxed)
+    }
+}
+
+/// A [`MemoryPool`] that prevents spillable reservations from using more than
+/// an even fraction of the available memory sans any unspillable reservations
+/// (i.e. `(pool_size - unspillable_memory) / num_spillable_reservations`)
+///
+///    ┌───────────────────────z──────────────────────z───────────────┐
+///    │                       z                      z               │
+///    │                       z                      z               │
+///    │       Spillable       z       Unspillable    z     Free      │
+///    │        Memory         z        Memory        z    Memory     │
+///    │                       z                      z               │
+///    │                       z                      z               │
+///    └───────────────────────z──────────────────────z───────────────┘
+///
+/// Unspillable memory is allocated in a first-come, first-serve fashion
+#[derive(Debug)]
+pub struct FairSpillPool {
+    /// The total memory limit
+    pool_size: usize,
+
+    state: Mutex<FairSpillPoolState>,
+}
+
+#[derive(Debug)]
+struct FairSpillPoolState {
+    /// The number of consumers that can spill
+    num_spill: usize,
+
+    /// The total amount of memory reserved that can be spilled
+    spillable: usize,
+
+    /// The total amount of memory reserved by consumers that cannot spill
+    unspillable: usize,
+}
+
+impl FairSpillPool {
+    /// Allocate up to `limit` bytes
+    pub fn new(pool_size: usize) -> Self {
+        Self {
+            pool_size,
+            state: Mutex::new(FairSpillPoolState {
+                num_spill: 0,
+                spillable: 0,
+                unspillable: 0,
+            }),
+        }
+    }
+}
+
+impl MemoryPool for FairSpillPool {
+    fn register(&self, consumer: &MemoryConsumer) {
+        if consumer.can_spill {
+            self.state.lock().num_spill += 1;
+        }
+    }
+
+    fn unregister(&self, consumer: &MemoryConsumer) {
+        if consumer.can_spill {
+            self.state.lock().num_spill -= 1;
+        }
+    }
+
+    fn grow(&self, reservation: &MemoryReservation, additional: usize) {
+        let mut state = self.state.lock();
+        match reservation.consumer.can_spill {
+            true => state.spillable += additional,
+            false => state.unspillable += additional,
+        }
+    }
+
+    fn shrink(&self, reservation: &MemoryReservation, shrink: usize) {
+        let mut state = self.state.lock();
+        match reservation.consumer.can_spill {
+            true => state.spillable -= shrink,
+            false => state.unspillable -= shrink,
+        }
+    }
+
+    fn try_grow(&self, reservation: &MemoryReservation, additional: usize) -> Result<()> {
+        let mut state = self.state.lock();
+
+        match reservation.consumer.can_spill {
+            true => {
+                // The total amount of memory available to spilling consumers
+                let spill_available = self.pool_size.saturating_sub(state.unspillable);
+
+                // No spiller may use more than their fraction of the memory available
+                let available = spill_available
+                    .checked_div(state.num_spill)
+                    .unwrap_or(spill_available);
+
+                if reservation.size + additional > available {
+                    return Err(insufficient_capacity_err(
+                        reservation,
+                        additional,
+                        available,
+                    ));
+                }
+                state.spillable += additional;
+            }
+            false => {
+                let available = self
+                    .pool_size
+                    .saturating_sub(state.unspillable + state.unspillable);

Review Comment:
   why sub state.unspillable twice here



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