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Suggest explicitly to stripe Python environment squashfs files #223

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5 changes: 4 additions & 1 deletion docs/guides/gb25.md
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Expand Up @@ -47,14 +47,17 @@ In the first round of GB runs we identified slow job startup times as a common c

With HPE we have identified that the most likely cause is file system contention loading dynamic libraries before `main()` starts.

The fix is to update how the squashfs file for the uenv or container used by your job is stored on the filesystem.
The fix is to update how the SquashFS file for the uenv or container used by your job is stored on the filesystem.

```console title="set lustre striping on uenv squashfs file"
$ uenv image inspect prgenv-gnu/24.11:v2 --format='{sqfs}'
/capstor/scratch/cscs/bcumming/.uenv-images/images/6068794b820fb4dd91019d020d6d98334a2f9fd23035a5e4a2f72f9dda5f1260/store.squashfs
$ lfs migrate --stripe-count 20 --stripe-size 1M $(uenv image inspect prgenv-gnu/24.11:v2 --format='{sqfs}')
```

If you are using a [SquashFS image for your Python environment][ref-guides-storage-venv],
you should also set the striping for that file.

As an additional precaution, we recommend to increase the default wait threshold for `MPI_Init` from 180 seconds to 300.
```console title="increase MPI initialization time-out"
$ export PMI_MMAP_SYNC_WAIT_TIME=300
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