andygrove commented on PR #3534:
URL:
https://github.com/apache/datafusion-comet/pull/3534#issuecomment-3909407007
## TPC-H q21 Memory Profile: Comet vs Gluten (SF100, Docker, 1 executor / 8
cores / 16 GiB)
Ran TPC-H query 21 with JVM memory profiling enabled (`--profile
--profile-interval 1.0`) for both engines on the same Docker cluster.
### Configuration
- **Spark:** 3.5.2 (docker image `comet-bench`)
- **Comet:** Java 17, `comet-baseline.jar`
- **Gluten:** Java 8,
`gluten-velox-bundle-spark3.5_2.12-linux_amd64-1.4.0.jar`
- **Cluster:** 1 executor, 8 cores, 16 GiB executor memory, 16 GiB off-heap
### Results (Executor 0)
Engine Wall-clock time
---Comet 80.03s
Gluten 43.55s
Delta +36.48s (Comet 1.84x slower)
Metric Comet Gluten
Delta
Peak memoryUsed 1.31 MB 1.91 MB
-605.79 KB (0.69x)
Peak JVMHeapMemory 5.90 GB 2.43 GB
+3.47 GB (2.43x)
Peak JVMOffHeapMemory 123.64 MB 116.36 MB
+7.27 MB (1.06x)
Peak OnHeapExecutionMemory 0.00 B 0.00 B
0
Peak OffHeapExecutionMemory 4.17 GB 2.79 GB
+1.38 GB (1.50x)
Peak OnHeapUnifiedMemory 9.49 MB 5.32 MB
+4.17 MB (1.78x)
Peak OffHeapUnifiedMemory 4.17 GB 2.79 GB
+1.38 GB (1.50x)
Peak ProcessTreeJVMRSSMemory 0.00 B 0.00 B
0
memoryUsed % of maxMemory 0.01% 0.01%
-0.00 pp
maxMemory (executor 0): Comet = 25.42 GB | Gluten = 24.36 GB
### Key Takeaways
- **Speed:** Gluten finished in 43.55s vs Comet's 80.03s (1.84x faster on
q21)
- **JVM Heap:** Comet peaked at 5.90 GB on-heap — **2.43x higher** than
Gluten's 2.43 GB. This is the single largest memory difference.
- **Off-Heap Execution Memory:** Comet used 4.17 GB vs Gluten's 2.79 GB
(1.50x more), reflecting native engine working memory during q21's multi-way
join + anti-join + aggregation.
- **JVM Off-Heap:** Roughly comparable (~120 MB each, only 6% difference).
- **On-Heap Execution:** Both 0 — expected since both engines execute
natively off-heap.
- **ProcessTreeJVMRSSMemory:** 0 for both (RSS tracking not enabled).
### Notes
- This is a single query (q21) on a single run — results may vary across
queries and iterations.
- The Docker image was updated to include both Java 8 (Gluten) and Java 17
(Comet), with a `--name` arg injection bugfix in `run.py`.
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