# Turning run\_combiner() performance for Hail local mode **URL:** \ **Category:** Hail Query & hailctl\ **Created:** [October 28, 2021, 8:09pm UTC](https://discuss.hail.is/t/turning-run-combiner-performance-for-hail-local-mode/2318 "2021-10-28T20:09:58Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![tpoterba](https://yyz2.discourse-cdn.com/flex036/user_avatar/discuss.hail.is/tpoterba/32/61_2.png) [@tpoterba](https://discuss.hail.is/u/tpoterba)\ **Post date:** [October 28, 2021, 11:10pm UTC](https://discuss.hail.is/t/turning-run-combiner-performance-for-hail-local-mode/2318/2 "2021-10-28T23:10:16Z")
Spark requires a special environment variable to configure JVM method. See this post: > [@How do I increase the memory or RAM available to the JVM when I start Hail through Python?](https://discuss.hail.is/t/how-do-i-increase-the-memory-or-ram-available-to-the-jvm-when-i-start-hail-through-python/133/2): > > You can set the memory using an environment variable: PYSPARK\_SUBMIT\_ARGS="--driver-memory 8g --executor-memory 8g pyspark-shell" ipython This will start an ipython notebook with 8 GB of memory. If you want ipython to always start with 8 GB of memory, you can add this to your .bashrc (or the equivalent file for your shell): export PYSPARK\_SUBMIT\_ARGS="--driver-memory 8g --executor-memory 8g pyspark-shell" I hope this helps! The executor summary certainly indicates there might be some GC thrashing happening. --- _[View the full topic](https://discuss.hail.is/t/turning-run-combiner-performance-for-hail-local-mode/2318)._