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new 4102fb852 feat: Change default off-heap memory pool from
`greedy_unified` to `fair_unified` (#2526)
4102fb852 is described below
commit 4102fb852cd6f1eabf79e890ba1ec9a33ed64db3
Author: Andy Grove <[email protected]>
AuthorDate: Mon Oct 6 08:42:11 2025 -0600
feat: Change default off-heap memory pool from `greedy_unified` to
`fair_unified` (#2526)
---
common/src/main/scala/org/apache/comet/CometConf.scala | 13 +++++++------
docs/source/user-guide/latest/configs.md | 2 +-
docs/source/user-guide/latest/tuning.md | 6 +++---
native/core/src/execution/memory_pools/config.rs | 10 ++++++----
native/core/src/execution/memory_pools/mod.rs | 2 +-
5 files changed, 18 insertions(+), 15 deletions(-)
diff --git a/common/src/main/scala/org/apache/comet/CometConf.scala
b/common/src/main/scala/org/apache/comet/CometConf.scala
index c2a5d0582..249b0ea6b 100644
--- a/common/src/main/scala/org/apache/comet/CometConf.scala
+++ b/common/src/main/scala/org/apache/comet/CometConf.scala
@@ -509,12 +509,13 @@ object CometConf extends ShimCometConf {
.createWithDefault(false)
val COMET_EXEC_MEMORY_POOL_TYPE: ConfigEntry[String] =
conf("spark.comet.exec.memoryPool")
- .doc("The type of memory pool to be used for Comet native execution. " +
- "When running Spark in on-heap mode, available pool types are 'greedy',
'fair_spill', " +
- "'greedy_task_shared', 'fair_spill_task_shared', 'greedy_global',
'fair_spill_global', " +
- "and `unbounded`. When running Spark in off-heap mode, available pool
types are " +
- "'unified' and `fair_unified`. The default pool type is
`greedy_task_shared` for on-heap " +
- s"mode and `unified` for off-heap mode. $TUNING_GUIDE.")
+ .doc(
+ "The type of memory pool to be used for Comet native execution. " +
+ "When running Spark in on-heap mode, available pool types are
'greedy', 'fair_spill', " +
+ "'greedy_task_shared', 'fair_spill_task_shared', 'greedy_global',
'fair_spill_global', " +
+ "and `unbounded`. When running Spark in off-heap mode, available pool
types are " +
+ "'greedy_unified' and `fair_unified`. The default pool type is
`greedy_task_shared` " +
+ s"for on-heap mode and `unified` for off-heap mode. $TUNING_GUIDE.")
.stringConf
.createWithDefault("default")
diff --git a/docs/source/user-guide/latest/configs.md
b/docs/source/user-guide/latest/configs.md
index bebca3c44..4c8fe810e 100644
--- a/docs/source/user-guide/latest/configs.md
+++ b/docs/source/user-guide/latest/configs.md
@@ -49,7 +49,7 @@ Comet provides the following configuration settings.
| spark.comet.exec.globalLimit.enabled | Whether to enable globalLimit by
default. | true |
| spark.comet.exec.hashJoin.enabled | Whether to enable hashJoin by default. |
true |
| spark.comet.exec.localLimit.enabled | Whether to enable localLimit by
default. | true |
-| spark.comet.exec.memoryPool | The type of memory pool to be used for Comet
native execution. When running Spark in on-heap mode, available pool types are
'greedy', 'fair_spill', 'greedy_task_shared', 'fair_spill_task_shared',
'greedy_global', 'fair_spill_global', and `unbounded`. When running Spark in
off-heap mode, available pool types are 'unified' and `fair_unified`. The
default pool type is `greedy_task_shared` for on-heap mode and `unified` for
off-heap mode. For more information, [...]
+| spark.comet.exec.memoryPool | The type of memory pool to be used for Comet
native execution. When running Spark in on-heap mode, available pool types are
'greedy', 'fair_spill', 'greedy_task_shared', 'fair_spill_task_shared',
'greedy_global', 'fair_spill_global', and `unbounded`. When running Spark in
off-heap mode, available pool types are 'greedy_unified' and `fair_unified`.
The default pool type is `greedy_task_shared` for on-heap mode and `unified`
for off-heap mode. For more infor [...]
| spark.comet.exec.project.enabled | Whether to enable project by default. |
true |
| spark.comet.exec.replaceSortMergeJoin | Experimental feature to force Spark
to replace SortMergeJoin with ShuffledHashJoin for improved performance. This
feature is not stable yet. For more information, refer to the Comet Tuning
Guide (https://datafusion.apache.org/comet/user-guide/tuning.html). | false |
| spark.comet.exec.shuffle.compression.codec | The codec of Comet native
shuffle used to compress shuffle data. lz4, zstd, and snappy are supported.
Compression can be disabled by setting spark.shuffle.compress=false. | lz4 |
diff --git a/docs/source/user-guide/latest/tuning.md
b/docs/source/user-guide/latest/tuning.md
index a35e32857..03aa8793b 100644
--- a/docs/source/user-guide/latest/tuning.md
+++ b/docs/source/user-guide/latest/tuning.md
@@ -116,13 +116,13 @@ Comet implements multiple memory pool implementations.
The type of pool can be s
The valid pool types for off-heap mode are:
-- `unified` (default when `spark.memory.offHeap.enabled=true` is set)
-- `fair_unified`
+- `fair_unified` (default when `spark.memory.offHeap.enabled=true` is set)
+- `greedy_unified`
Both of these pools share off-heap memory between Spark and Comet. This
approach is referred to as
unified memory management. The size of the pool is specified by
`spark.memory.offHeap.size`.
-The `unified` pool type implements a greedy first-come first-serve limit. This
pool works well for queries that do not
+The `greedy_unified` pool type implements a greedy first-come first-serve
limit. This pool works well for queries that do not
need to spill or have a single spillable operator.
The `fair_unified` pool type prevents operators from using more than an even
fraction of the available memory
diff --git a/native/core/src/execution/memory_pools/config.rs
b/native/core/src/execution/memory_pools/config.rs
index f9a0e23f4..ebab45b11 100644
--- a/native/core/src/execution/memory_pools/config.rs
+++ b/native/core/src/execution/memory_pools/config.rs
@@ -19,7 +19,7 @@ use crate::errors::{CometError, CometResult};
#[derive(Copy, Clone, PartialEq, Eq)]
pub(crate) enum MemoryPoolType {
- Unified,
+ GreedyUnified,
FairUnified,
Greedy,
FairSpill,
@@ -62,12 +62,14 @@ pub(crate) fn parse_memory_pool_config(
let pool_size = memory_limit as usize;
let memory_pool_config = if off_heap_mode {
match memory_pool_type.as_str() {
- "fair_unified" =>
MemoryPoolConfig::new(MemoryPoolType::FairUnified, pool_size),
- "default" | "unified" => {
+ "default" | "fair_unified" => {
+ MemoryPoolConfig::new(MemoryPoolType::FairUnified, pool_size)
+ }
+ "greedy_unified" => {
// the `unified` memory pool interacts with Spark's memory
pool to allocate
// memory therefore does not need a size to be explicitly set.
The pool size
// shared with Spark is set by `spark.memory.offHeap.size`.
- MemoryPoolConfig::new(MemoryPoolType::Unified, 0)
+ MemoryPoolConfig::new(MemoryPoolType::GreedyUnified, 0)
}
_ => {
return Err(CometError::Config(format!(
diff --git a/native/core/src/execution/memory_pools/mod.rs
b/native/core/src/execution/memory_pools/mod.rs
index 3e40dc692..fc6a81a5e 100644
--- a/native/core/src/execution/memory_pools/mod.rs
+++ b/native/core/src/execution/memory_pools/mod.rs
@@ -40,7 +40,7 @@ pub(crate) fn create_memory_pool(
) -> Arc<dyn MemoryPool> {
const NUM_TRACKED_CONSUMERS: usize = 10;
match memory_pool_config.pool_type {
- MemoryPoolType::Unified => {
+ MemoryPoolType::GreedyUnified => {
// Set Comet memory pool for native
let memory_pool =
CometUnifiedMemoryPool::new(comet_task_memory_manager,
task_attempt_id);
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