Adding new env variables for TPU backends. (#1755)

# What does this PR do?


On TPU (and probably inferentia). The model needs to know right off the
bat about BATCH_SIZE and MAX_TOTAL_TOKENS (since the entire cache will
be determined by both).

This PR sends that information to the shards to they can allocate
accordingly. Should be no-op for other backends.
<!--
Congratulations! You've made it this far! You're not quite done yet
though.

Once merged, your PR is going to appear in the release notes with the
title you set, so make sure it's a great title that fully reflects the
extent of your awesome contribution.

Then, please replace this with a description of the change and which
issue is fixed (if applicable). Please also include relevant motivation
and context. List any dependencies (if any) that are required for this
change.

Once you're done, someone will review your PR shortly (see the section
"Who can review?" below to tag some potential reviewers). They may
suggest changes to make the code even better. If no one reviewed your PR
after a week has passed, don't hesitate to post a new comment
@-mentioning the same persons---sometimes notifications get lost.
-->

<!-- Remove if not applicable -->

Fixes # (issue)


## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the
other checks if that's the case).
- [ ] Did you read the [contributor
guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?
- [ ] Was this discussed/approved via a Github issue or the
[forum](https://discuss.huggingface.co/)? Please add a link
      to it if that's the case.
- [ ] Did you make sure to update the documentation with your changes?
Here are the
[documentation
guidelines](https://github.com/huggingface/transformers/tree/main/docs),
and
[here are tips on formatting
docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests?


## Who can review?

Anyone in the community is free to review the PR once the tests have
passed. Feel free to tag
members/contributors who may be interested in your PR.

<!-- Your PR will be replied to more quickly if you can figure out the
right person to tag with @


@OlivierDehaene OR @Narsil

 -->

Author: Narsil

launcher/src/main.rs

@@ -448,6 +448,8 @@ fn shard_manager(
     cuda_memory_fraction: f32,
     rope_scaling: Option<RopeScaling>,
     rope_factor: Option<f32>,
+    max_total_tokens: usize,
+    max_batch_size: Option<usize>,
     otlp_endpoint: Option<String>,
     status_sender: mpsc::Sender<ShardStatus>,
     shutdown: Arc<AtomicBool>,
@@ -512,6 +514,7 @@ fn shard_manager(
         (Some(scaling), Some(factor)) => Some((scaling, factor)),
         (None, Some(factor)) => Some((RopeScaling::Linear, factor)),
     };
+
     // OpenTelemetry
     if let Some(otlp_endpoint) = otlp_endpoint {
         shard_args.push("--otlp-endpoint".to_string());
@@ -564,6 +567,14 @@ fn shard_manager(
         envs.push(("ROPE_FACTOR".into(), factor.to_string().into()));
     }
 
+    envs.push((
+        "MAX_TOTAL_TOKENS".into(),
+        max_total_tokens.to_string().into(),
+    ));
+    if let Some(max_batch_size) = max_batch_size {
+        envs.push(("MAX_BATCH_SIZE".into(), max_batch_size.to_string().into()));
+    }
+
     // If huggingface_hub_cache is some, pass it to the shard
     // Useful when running inside a docker container
     if let Some(huggingface_hub_cache) = huggingface_hub_cache {
@@ -967,6 +978,7 @@ fn spawn_shards(
     num_shard: usize,
     args: &Args,
     cuda_graphs: Vec<usize>,
+    max_total_tokens: usize,
     shutdown: Arc<AtomicBool>,
     shutdown_receiver: &mpsc::Receiver<()>,
     shutdown_sender: mpsc::Sender<()>,
@@ -998,6 +1010,7 @@ fn spawn_shards(
         let cuda_memory_fraction = args.cuda_memory_fraction;
         let rope_scaling = args.rope_scaling;
         let rope_factor = args.rope_factor;
+        let max_batch_size = args.max_batch_size;
         thread::spawn(move || {
             shard_manager(
                 model_id,
@@ -1020,6 +1033,8 @@ fn spawn_shards(
                 cuda_memory_fraction,
                 rope_scaling,
                 rope_factor,
+                max_total_tokens,
+                max_batch_size,
                 otlp_endpoint,
                 status_sender,
                 shutdown,
@@ -1474,6 +1489,7 @@ fn main() -> Result<(), LauncherError> {
         num_shard,
         &args,
         cuda_graphs,
+        max_total_tokens,
         shutdown.clone(),
         &shutdown_receiver,
         shutdown_sender,