From 2ab66e112d596a61ec6b583ba7fc0d7911783abe Mon Sep 17 00:00:00 2001
From: Evan <evanev7@gmail.com>
Date: Tue, 3 Mar 2026 15:25:57 +0000
Subject: [PATCH] or maybe this

---
 src/exo/master/placement.py       | 12 +++++++++++-
 src/exo/master/placement_utils.py |  7 ++++++-
 src/exo/shared/types/topology.py  |  1 +
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/exo/master/placement.py b/src/exo/master/placement.py
index d6f382ec..ba058903 100644
--- a/src/exo/master/placement.py
+++ b/src/exo/master/placement.py
@@ -69,7 +69,17 @@ def place_instance(
     required_nodes: set[NodeId] | None = None,
 ) -> dict[InstanceId, Instance]:
     cycles = topology.get_cycles()
-    candidate_cycles = list(filter(lambda it: len(it) >= command.min_nodes, cycles))
+    candidate_cycles = filter(lambda it: len(it) >= command.min_nodes, cycles)
+    nodes_with_exo = set[NodeId]()
+    for instance in current_instances.values():
+        nodes_with_exo |= instance.shard_assignments.node_to_runner.keys()
+    candidate_cycles = [
+        Cycle(
+            cycle.node_ids,
+            has_other_placement=any(node in nodes_with_exo for node in cycle),
+        )
+        for cycle in candidate_cycles
+    ]
 
     # Filter to cycles containing all required nodes (subset matching)
     if required_nodes:
diff --git a/src/exo/master/placement_utils.py b/src/exo/master/placement_utils.py
index a8a2e70b..ff800c5e 100644
--- a/src/exo/master/placement_utils.py
+++ b/src/exo/master/placement_utils.py
@@ -29,7 +29,12 @@ def filter_cycles_by_memory(
             continue
 
         total_mem = sum(
-            (node_memory[node_id].ram_total for node_id in cycle.node_ids),
+            (
+                node_memory[node_id].ram_available
+                if cycle.has_other_placement
+                else node_memory[node_id].ram_total
+                for node_id in cycle.node_ids
+            ),
             start=Memory(),
         )
         if total_mem >= required_memory:
diff --git a/src/exo/shared/types/topology.py b/src/exo/shared/types/topology.py
index c388c6ab..e2f29d02 100644
--- a/src/exo/shared/types/topology.py
+++ b/src/exo/shared/types/topology.py
@@ -9,6 +9,7 @@ from exo.utils.pydantic_ext import FrozenModel
 @dataclass(frozen=True)
 class Cycle:
     node_ids: list[NodeId]
+    has_other_placement: bool = False
 
     def __len__(self) -> int:
         return self.node_ids.__len__()