[NPU] Fix failed test cases in pr‑test‑npu and improve execution efficiency (#38112)

Co-authored-by: Even Zhou <even.y.zhou@outlook.com>
Co-authored-by: sglang-npu-bot <sglangnpu@163.com>

python/sglang/multimodal_gen/test/server/ascend/conftest.py

@@ -0,0 +1,111 @@
+"""Ascend NPU conftest: evict stale model page cache before each test case.
+
+Memory-capped CI runners (e.g. a 128 GiB cgroup on the 4-NPU A3 pool) count
+reclaimable page cache from previously loaded models in cgroup
+``memory.current``, so ``host_memory_available_bytes()`` reports ~0 GiB
+available and layerwise offload degrades to the slow checkpoint-mapping path
+(observed as multi-fold latency regressions on minimax/mova perf cases).
+Dropping the page cache of non-current models before each case keeps the host
+memory budget healthy for the upcoming model load.
+"""
+
+from __future__ import annotations
+
+import os
+import sys
+
+import pytest
+
+from sglang.multimodal_gen.test.server.ascend.testcase_configs_npu import (
+    MODELSCOPE_MODEL_WEIGHTS_DIR,
+)
+
+_CGROUP_V2_CURRENT = "/sys/fs/cgroup/memory.current"
+_CGROUP_V1_USAGE = "/sys/fs/cgroup/memory/memory.usage_in_bytes"
+
+
+def _read_cgroup_memory_current() -> str:
+    """Best-effort read of the container's cgroup memory usage in bytes."""
+    for path in (_CGROUP_V2_CURRENT, _CGROUP_V1_USAGE):
+        try:
+            with open(path, encoding="utf-8") as handle:
+                return handle.read().strip()
+        except OSError:
+            continue
+    return "unknown"
+
+
+def _collect_case_weight_paths(server_args) -> set[str]:
+    """Real paths of every weight dir/file the upcoming case will load."""
+    paths = set()
+    for attr in ("model_path", "transformer_weights_path", "lora_path"):
+        value = getattr(server_args, attr, None)
+        if value:
+            paths.add(os.path.realpath(value))
+    for attr in ("component_paths", "component_weights_paths"):
+        mapping = getattr(server_args, attr, None)
+        if mapping:
+            paths.update(os.path.realpath(value) for value in mapping.values() if value)
+    return paths
+
+
+def _evict_dir_page_cache(root: str, keep: set[str]) -> tuple[int, int]:
+    """Drop page cache of files under ``root`` except those under ``keep``.
+
+    ``posix_fadvise(POSIX_FADV_DONTNEED)`` only drops clean cache pages, so it
+    is safe on read-only model checkpoints.
+    """
+    evicted_files = 0
+    evicted_bytes = 0
+    for dirpath, _dirnames, filenames in os.walk(root):
+        for name in filenames:
+            path = os.path.realpath(os.path.join(dirpath, name))
+            if any(path == kept or path.startswith(kept + os.sep) for kept in keep):
+                continue
+            try:
+                fd = os.open(path, os.O_RDONLY)
+                try:
+                    os.posix_fadvise(fd, 0, 0, os.POSIX_FADV_DONTNEED)
+                    evicted_bytes += os.fstat(fd).st_size
+                    evicted_files += 1
+                finally:
+                    os.close(fd)
+            except OSError:
+                continue
+    return evicted_files, evicted_bytes
+
+
+@pytest.fixture(autouse=True)
+def _evict_stale_model_page_cache(request):
+    """Evict page cache of models not used by the upcoming test case.
+
+    For parametrized diffusion cases the current model's weights are kept so
+    the server load is not penalized; only stale cache from previous cases is
+    dropped. For standalone (non-parametrized) tests everything is dropped.
+    """
+    if sys.platform != "linux" or not os.path.isdir(MODELSCOPE_MODEL_WEIGHTS_DIR):
+        yield
+        return
+
+    keep: set[str] = set()
+    callspec = getattr(request.node, "callspec", None)
+    if callspec is not None:
+        for value in callspec.params.values():
+            server_args = getattr(value, "server_args", None)
+            if server_args is not None:
+                keep |= _collect_case_weight_paths(server_args)
+
+    before = _read_cgroup_memory_current()
+    print(
+        f"[CONFTEST] Evicting stale model page cache before {request.node.nodeid} "
+        f"(keep: {sorted(os.path.basename(p) for p in keep) or 'none'})"
+    )
+    print(f"[CONFTEST] cgroup memory.current before: {before}")
+
+    total_files, total_bytes = _evict_dir_page_cache(MODELSCOPE_MODEL_WEIGHTS_DIR, keep)
+    print(
+        f"[CONFTEST] Page cache eviction summary: {total_files} files, "
+        f"{total_bytes / 1024**3:.2f} GiB evicted"
+    )
+    print(f"[CONFTEST] cgroup memory.current after: {_read_cgroup_memory_current()}")
+    yield

python/sglang/multimodal_gen/test/server/ascend/testcase_configs_npu.py

@@ -176,6 +176,7 @@ TWO_NPU_CASES: list[DiffusionTestCase] = [
                 "SGLANG_CACHE_DIT_TAYLORSEER": "true",
                 "SGLANG_CACHE_DIT_TS_ORDER": "2",
                 "HCCL_BUFFSIZE": "256",
+                "SGLANG_DIFFUSION_TEST_FORCE_HOST_AVAILABLE_GIB": "64",
             },
         ),
         DiffusionSamplingParams(
@@ -227,6 +228,9 @@ TWO_NPU_CASES: list[DiffusionTestCase] = [
             num_gpus=2,
             tp_size=2,
             dit_layerwise_offload=True,
+            env_vars={
+                "SGLANG_DIFFUSION_TEST_FORCE_HOST_AVAILABLE_GIB": "96",
+            },
             extras=EXTRAS_DISABLE_WARMUP,
         ),
         run_consistency_check=False,