Jax persistent compilation cache user guide.

This user guide covers using the cache on local filesystems
and Google Cloud.

PiperOrigin-RevId: 623236335

docs/persistent_compilation_cache.md

@@ -0,0 +1,74 @@
+# Persistent Compilation Cache
+
+JAX has an optional disk cache for compiled programs. If enabled, JAX will
+store copies of compiled programs on disk, which can save recompilation time
+when running the same or similar tasks repeatedly.
+
+## Usage
+
+The compilation cache is enabled when the
+[cache-location](https://github.com/google/jax/blob/jax-v0.4.26/jax/_src/config.py#L1206)
+is set. This should be done prior to the first compilation. Set the location as
+follows:
+
+```
+import jax
+
+# Make sure this is called before jax runs any operations!
+jax.config.update("jax_compilation_cache_dir", "cache-location")
+```
+
+See the sections below for more detail on `cache-location`.
+
+[`set_cache_dir()`](https://github.com/google/jax/blob/jax-v0.4.26/jax/experimental/compilation_cache/compilation_cache.py#L18)
+is an alternate way of setting `cache-location`.
+
+### Local filesystem
+
+`cache-location` can be a directory on the local filesystem. For example:
+
+```
+import jax
+
+jax.config.update("jax_compilation_cache_dir", "/tmp/jax-cache")
+```
+
+Note: the cache does not have an eviction mechanism implemented. If the
+cache-location is a directory in the local filesystem, its size will continue
+to grow unless files are manually deleted.
+
+### Google Cloud
+
+When running on Google Cloud, the compilation cache can be placed on a Google
+Cloud Storage (GCS) bucket. We recommend the following configuration:
+
+*  Create the bucket in the same region as where the workload will run.
+
+*  Create the bucket in the same project as the workload’s VM(s). Ensure that
+   permissions are set so that the VM(s) can write to the bucket.
+
+*  There is no need for replication for smaller workloads. Larger workloads
+   could benefit from replication.
+
+*  Use “Standard” for the default storage class for the bucket.
+
+*  Set the soft delete policy to its shortest: 7 days.
+
+*  Set the object lifecycle to the expected duration of the workload run.
+   For example, if the workload is expected to run for 10 days, set the object
+   lifecycle to 10 days. That should cover restarts that occur during the entire
+   run. Use `age` for the lifecycle condition and `Delete` for the action. See
+   [Object Lifecycle Management](https://cloud.google.com/storage/docs/lifecycle)
+   for details. If the object lifecycle is not set, the cache will continue to
+   grow since there is no eviction mechanism implemented.
+
+*  All encryption policies are supported.
+
+Assuming that `gs://jax-cache` is the GCS bucket, set `cache-location` as
+follows:
+
+```
+import jax
+
+jax.config.update("jax_compilation_cache_dir", "gs://jax-cache")
+```

docs/user_guides.rst

@@ -15,7 +15,7 @@ or deployed codebases.
    device_memory_profiling
    debugging/index
    gpu_performance_tips
-
+   persistent_compilation_cache
 
 .. toctree::
    :maxdepth: 1