diff --git a/test_runner/fixtures/pageserver/http.py b/test_runner/fixtures/pageserver/http.py
index f1e3d1a309..c7cea4ec04 100644
--- a/test_runner/fixtures/pageserver/http.py
+++ b/test_runner/fixtures/pageserver/http.py
@@ -117,6 +117,9 @@ class LayerMapInfo:
     def image_layers(self) -> List[HistoricLayerInfo]:
         return [x for x in self.historic_layers if x.kind == "Image"]
 
+    def delta_l0_layers(self) -> List[HistoricLayerInfo]:
+        return [x for x in self.historic_layers if x.kind == "Delta" and x.l0]
+
     def historic_by_name(self) -> Set[str]:
         return set(x.layer_file_name for x in self.historic_layers)
 
diff --git a/test_runner/performance/test_compaction.py b/test_runner/performance/test_compaction.py
index 326c4f5c6f..077b76104c 100644
--- a/test_runner/performance/test_compaction.py
+++ b/test_runner/performance/test_compaction.py
@@ -2,6 +2,7 @@ from contextlib import closing
 
 import pytest
 from fixtures.compare_fixtures import NeonCompare
+from fixtures.log_helper import log
 from fixtures.neon_fixtures import wait_for_last_flush_lsn
 
 
@@ -56,3 +57,98 @@ def test_compaction(neon_compare: NeonCompare):
         pageserver_http.timeline_compact(tenant_id, timeline_id)
 
     neon_compare.report_size()
+
+
+def test_compaction_l0_memory(neon_compare: NeonCompare):
+    """
+    Generate a large stack of L0s pending compaction into L1s, and
+    measure the pageserver's peak RSS while doing so
+    """
+
+    env = neon_compare.env
+    pageserver_http = env.pageserver.http_client()
+
+    tenant_id, timeline_id = env.neon_cli.create_tenant(
+        conf={
+            # Initially disable compaction so that we will build up a stack of L0s
+            "compaction_period": "0s",
+            "gc_period": "0s",
+        }
+    )
+    neon_compare.tenant = tenant_id
+    neon_compare.timeline = timeline_id
+
+    endpoint = env.endpoints.create_start(
+        "main", tenant_id=tenant_id, config_lines=["shared_buffers=512MB"]
+    )
+
+    # Read tenant effective config and assert on checkpoint_distance and compaction_threshold,
+    # as we do want to test with defaults (to be same as the field), but this test's workload size makes assumptions about them.
+    #
+    # If these assertions fail, it probably means we changed the default.
+    tenant_conf = pageserver_http.tenant_config(tenant_id)
+    assert tenant_conf.effective_config["checkpoint_distance"] == 256 * 1024 * 1024
+    assert tenant_conf.effective_config["compaction_threshold"] == 10
+
+    # Aim to write about 20 L0s, so that we will hit the limit on how many
+    # to compact at once
+    with closing(endpoint.connect()) as conn:
+        with conn.cursor() as cur:
+            for i in range(200):
+                cur.execute(f"create table tbl{i} (i int, j int);")
+                cur.execute(f"insert into tbl{i} values (generate_series(1, 1000), 0);")
+                for j in range(100):
+                    cur.execute(f"update tbl{i} set j = {j};")
+
+    wait_for_last_flush_lsn(env, endpoint, tenant_id, timeline_id)
+    endpoint.stop()
+
+    # Check we have generated the L0 stack we expected
+    layers = pageserver_http.layer_map_info(tenant_id, timeline_id)
+    initial_l0s = len(layers.delta_l0_layers())
+    initial_l0s_size = sum(x.layer_file_size for x in layers.delta_l0_layers())
+    log.info(f"l0s before compaction {initial_l0s} ({initial_l0s_size})")
+
+    def rss_hwm():
+        v = pageserver_http.get_metric_value("libmetrics_maxrss_kb")
+        assert v is not None
+        assert v > 0
+        return v * 1024
+
+    before = rss_hwm()
+    pageserver_http.timeline_compact(tenant_id, timeline_id)
+    after = rss_hwm()
+
+    log.info(f"RSS across compaction: {before} -> {after} (grew {after - before})")
+
+    layers = pageserver_http.layer_map_info(tenant_id, timeline_id)
+    final_l0s_size = sum(x.layer_file_size for x in layers.delta_l0_layers())
+    log.info(f"l0s after compaction {len(layers.delta_l0_layers())} ({final_l0s_size})")
+
+    assert after > before  # If we didn't use some memory the test is probably buggy
+    compaction_mapped_rss = after - before
+
+    # During L0 compaction, we require as much memory as the physical size of what we compacted, and then some,
+    # because the key->value mapping in L0s compaction is exhaustive, non-streaming, and does not de-duplicate
+    # repeated references to the same key.
+    #
+    # To be fixed in https://github.com/neondatabase/neon/issues/8184, after which
+    # this memory estimate can be revised far downwards to something that doesn't scale
+    # linearly with the layer sizes.
+    MEMORY_ESTIMATE = (initial_l0s_size - final_l0s_size) * 1.25
+
+    # If we find that compaction is using more memory, this may indicate a regression
+    assert compaction_mapped_rss < MEMORY_ESTIMATE
+
+    # If we find that compaction is using <0.5 the expected memory then:
+    # - maybe we made a big efficiency improvement, in which case update the test
+    # - maybe something is functionally wrong with the test and it's not driving the system as expected
+    assert compaction_mapped_rss > MEMORY_ESTIMATE / 2
+
+    # We should have compacted some but not all of the l0s, based on the limit on how much
+    # l0 to compact in one go
+    assert len(layers.delta_l0_layers()) > 0
+    assert len(layers.delta_l0_layers()) < initial_l0s
+
+    # The pageserver should have logged when it hit the compaction size limit
+    env.pageserver.assert_log_contains(".*hit max delta layer size limit.*")