[GLM-5.3-Flash] Reduce KPool planning synchronization and overlap indexer preparation (#39695)

Co-authored-by: Xinyuan Tong <xinyuantong.cs@gmail.com>

python/sglang/srt/batch_overlap/two_batch_overlap.py

@@ -705,6 +705,7 @@ class TboForwardBatchPreparer:
 
         for key in [
             "req_pool_indices",
+            "req_pool_indices_cpu",
             "seq_lens",
             "seq_lens_cpu",
             "extend_seq_lens",

python/sglang/srt/layers/attention/dsa/dsa_indexer_kpool.py

@@ -14,6 +14,7 @@ from sglang.srt.layers.attention.dsa.dsa_indexer import (
     rotate_activation,
 )
 from sglang.srt.layers.attention.dsa.dsa_topk_backend import TopkTransformMethod
+from sglang.srt.layers.attention.dsa.utils import dsa_use_prefill_cp
 from sglang.srt.layers.layernorm import LayerNorm
 from sglang.srt.layers.utils import MultiPlatformOp
 from sglang.srt.utils import add_prefix, ceil_align, is_cuda, is_hip, is_npu
@@ -163,6 +164,36 @@ class IndexerKPool(MultiPlatformOp):
         weights = weights.unsqueeze(-1) * q_scale * self.softmax_scale
         return weights
 
+    @torch.compile(dynamic=True)
+    def _project_and_scale_head_gates(self, x: torch.Tensor) -> torch.Tensor:
+        weights, _ = self.weights_proj(x.float())
+        return weights * self.n_heads**-0.5
+
+    @torch.compile(dynamic=True)
+    def _apply_q_scale_and_softmax_scale(
+        self, weights: torch.Tensor, q_scale: torch.Tensor
+    ) -> torch.Tensor:
+        return weights.unsqueeze(-1) * q_scale * self.softmax_scale
+
+    def _resolve_head_gate_weights(self, x, q_scale, head_weights):
+        if head_weights is not None:
+            return self._apply_q_scale_and_softmax_scale(head_weights, q_scale)
+        return self._get_logits_head_gate(x, q_scale)
+
+    def _can_overlap_prefill(
+        self,
+        forward_batch: ForwardBatch,
+        return_indices: bool,
+    ) -> bool:
+        return (
+            self.alt_stream is not None
+            and return_indices
+            and forward_batch.forward_mode.is_extend_without_speculative()
+            and not get_is_capture_mode()
+            and not is_in_breakable_cuda_graph()
+            and not dsa_use_prefill_cp(forward_batch)
+        )
+
     @staticmethod
     def _get_index_k_read_buffer(pool, layer_id: int) -> torch.Tensor:
         if hasattr(pool, "get_broadcastable_index_k_with_scale_buffer"):
@@ -538,8 +569,11 @@ class IndexerKPool(MultiPlatformOp):
         enable_dual_stream: bool,
         forward_batch: ForwardBatch,
         precompute_compress_gate: bool = False,
+        precompute_head_gate: bool = False,
     ):
         gate_score = None
+        head_weights = None
+        apply_rope = not self.skip_rope and self.rope_head_dim > 0
         if enable_dual_stream:
             current_stream = torch.cuda.current_stream()
             self.alt_stream.wait_stream(current_stream)
@@ -557,6 +591,10 @@ class IndexerKPool(MultiPlatformOp):
                     [self.rope_head_dim, self.head_dim - self.rope_head_dim],
                     dim=-1,
                 )
+            if precompute_head_gate:
+                head_weights = self._project_and_scale_head_gates(x)
+            if not apply_rope:
+                query = rotate_activation(query)
             with torch.cuda.stream(self.alt_stream):
                 key, _ = self.wk(x)
                 key = self.k_norm(key)
@@ -584,15 +622,16 @@ class IndexerKPool(MultiPlatformOp):
                 key, [self.rope_head_dim, self.head_dim - self.rope_head_dim], dim=-1
             )
 
-        if not self.skip_rope:
+        if apply_rope:
             q_rope, k_rope = self.rotary_emb(positions, q_rope, k_rope)
 
             query[..., : self.rope_head_dim] = q_rope
             key[..., : self.rope_head_dim] = k_rope
 
-        query = rotate_activation(query)
+        if apply_rope or not enable_dual_stream:
+            query = rotate_activation(query)
 
-        return query, key, gate_score
+        return query, key, gate_score, head_weights
 
     def _get_k_bf16(
         self,
@@ -1293,7 +1332,7 @@ class IndexerKPool(MultiPlatformOp):
         assert plan is not None, "DSA kpool target_verify requires kpool_write_plan"
         num_draft_tokens = plan.num_draft_tokens
 
-        query, key, gate_score_maybe = self._get_q_k_bf16(
+        query, key, gate_score_maybe, head_weights = self._get_q_k_bf16(
             q_lora,
             x,
             positions,
@@ -1302,6 +1341,7 @@ class IndexerKPool(MultiPlatformOp):
             precompute_compress_gate=(
                 enable_dual_stream and self.compress_gate_stream is not None
             ),
+            precompute_head_gate=enable_dual_stream and return_indices,
         )
 
         pool = get_token_to_kv_pool()
@@ -1340,7 +1380,7 @@ class IndexerKPool(MultiPlatformOp):
                 self.alt_stream.wait_stream(self.compress_gate_stream)
             if return_indices:
                 q_fp8, q_scale = act_quant(query, self.block_size, self.scale_fmt)
-                weights = self._get_logits_head_gate(x, q_scale)
+                weights = self._resolve_head_gate_weights(x, q_scale, head_weights)
             with torch.cuda.stream(self.alt_stream):
                 _compress_write()
             current_stream.wait_stream(self.alt_stream)
@@ -1348,7 +1388,7 @@ class IndexerKPool(MultiPlatformOp):
             _compress_write()
             if return_indices:
                 q_fp8, q_scale = act_quant(query, self.block_size, self.scale_fmt)
-                weights = self._get_logits_head_gate(x, q_scale)
+                weights = self._resolve_head_gate_weights(x, q_scale, head_weights)
 
         if not return_indices:
             return None
@@ -1476,44 +1516,24 @@ class IndexerKPool(MultiPlatformOp):
             and forward_batch.forward_mode.is_decode_or_idle()
             and self.compress_gate_stream is not None
         )
-        query, key, gate_score = self._get_q_k_bf16(
+        query, key, gate_score, head_weights = self._get_q_k_bf16(
             q_lora,
             x,
             positions,
             enable_dual_stream,
             forward_batch=forward_batch,
             precompute_compress_gate=precompute_compress_gate,
+            precompute_head_gate=enable_dual_stream and return_indices,
         )
 
-        weights = None
+        has_kpool_extend_plan = metadata.attn_metadata.kpool_extend_plan is not None
-        kpool_extend_cache = None
+        is_prefill = forward_batch.forward_mode.is_extend_without_speculative()
-        if enable_dual_stream and forward_batch.forward_mode.is_decode_or_idle():
+        defer_kpool_cache_write = (
-            current_stream = torch.cuda.current_stream()
+            is_prefill and return_indices and not has_kpool_extend_plan
-            self.alt_stream.wait_stream(current_stream)
+        )
-            if gate_score is not None:
+
-                self.alt_stream.wait_stream(self.compress_gate_stream)
+        def compress_write():
-            with torch.cuda.stream(self.alt_stream):
+            return self._compress_write(
-                self._compress_write(
-                    x=x,
-                    key=key,
-                    positions=positions,
-                    forward_batch=forward_batch,
-                    layer_id=layer_id,
-                    metadata=metadata,
-                    gate_score=gate_score,
-                )
-            q_fp8, q_scale = act_quant(query, self.block_size, self.scale_fmt)
-            weights = self._get_logits_head_gate(x, q_scale)
-            current_stream.wait_stream(self.alt_stream)
-        else:
-            q_fp8, q_scale = act_quant(query, self.block_size, self.scale_fmt)
-            has_kpool_extend_plan = metadata.attn_metadata.kpool_extend_plan is not None
-            defer_kpool_cache_write = (
-                forward_batch.forward_mode.is_extend_without_speculative()
-                and return_indices
-                and not has_kpool_extend_plan
-            )
-            kpool_extend_cache = self._compress_write(
                 x=x,
                 key=key,
                 positions=positions,
@@ -1521,20 +1541,33 @@ class IndexerKPool(MultiPlatformOp):
                 layer_id=layer_id,
                 metadata=metadata,
                 gate_score=gate_score,
-                return_compressed=(
+                return_compressed=is_prefill and return_indices,
-                    forward_batch.forward_mode.is_extend_without_speculative()
-                    and return_indices
-                ),
                 write_cache=not defer_kpool_cache_write,
             )
-            if (
-                forward_batch.forward_mode.is_extend_without_speculative()
-                and not return_indices
-            ):
-                return None
 
-        if weights is None:
+        overlap_decode = (
-            weights = self._get_logits_head_gate(x, q_scale)
+            enable_dual_stream and forward_batch.forward_mode.is_decode_or_idle()
+        )
+        if overlap_decode or self._can_overlap_prefill(forward_batch, return_indices):
+            current_stream = torch.cuda.current_stream()
+            self.alt_stream.wait_stream(current_stream)
+            if gate_score is not None:
+                self.alt_stream.wait_stream(self.compress_gate_stream)
+            with torch.cuda.stream(self.alt_stream):
+                kpool_extend_cache = compress_write()
+            if return_indices:
+                q_fp8, q_scale = act_quant(query, self.block_size, self.scale_fmt)
+                weights = self._resolve_head_gate_weights(x, q_scale, head_weights)
+            current_stream.wait_stream(self.alt_stream)
+        else:
+            if return_indices:
+                q_fp8, q_scale = act_quant(query, self.block_size, self.scale_fmt)
+            kpool_extend_cache = compress_write()
+            if return_indices:
+                weights = self._resolve_head_gate_weights(x, q_scale, head_weights)
+
+        if not return_indices:
+            return None
 
         if is_cuda():
             if (

python/sglang/srt/layers/attention/dsa/kpool_plan.py

@@ -245,7 +245,10 @@ def _kpool_cpu_plan(
     if isinstance(extend_seq_lens_cpu, torch.Tensor):
         extend_seq_lens_cpu = extend_seq_lens_cpu.tolist()
     seq_lens_cpu = forward_batch.seq_lens_cpu.tolist()
-    req_pool_indices_cpu = forward_batch.req_pool_indices.tolist()
+    req_pool_indices_cpu = getattr(forward_batch, "req_pool_indices_cpu", None)
+    if req_pool_indices_cpu is None:
+        req_pool_indices_cpu = forward_batch.req_pool_indices
+    req_pool_indices_cpu = req_pool_indices_cpu.tolist()
 
     _append_compress_rows(
         plan,
@@ -411,7 +414,9 @@ def _kpool_plan_to_gpu(
     if need_paged:
         req_to_token = get_req_to_token_pool().req_to_token
         ragged_paged_page_table_row_index = torch.repeat_interleave(
-            local_req_pool_indices.to(torch.int32), ragged_q_len_t
+            local_req_pool_indices.to(torch.int32),
+            ragged_q_len_t,
+            output_size=sum(cpu.ragged_q_len),
         )
         ragged_paged_page_table = req_to_token
 

python/sglang/srt/managers/schedule_batch.py

@@ -2348,8 +2348,6 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
     # A full prefill has one result but can span several run_batch calls.
     split_prefill_start: Optional[Tuple[int, float]] = None
 
-    # CPU mirror of req_pool_indices; schedule-path only (used in overlap_utils,
-    # not read by ForwardBatch), stale in spec draft window
     req_pool_indices_cpu: torch.Tensor = None  # shape: [b], int64
 
     # Forward-pass metrics
@@ -3770,6 +3768,7 @@ class ScheduleBatch(ScheduleBatchDisaggregationDecodeMixin):
             prefix_lens=self.prefix_lens,
             req_to_token_pool=self.req_to_token_pool,
             req_pool_indices=self.req_pool_indices,
+            req_pool_indices_cpu=self.req_pool_indices_cpu,
             model_config=self.model_config,
             forward_mode=self.forward_mode,
             out_cache_loc=self.out_cache_loc,

python/sglang/srt/model_executor/forward_batch_info.py

@@ -547,6 +547,8 @@ class ForwardBatch(ForwardBatchDeepSeekMHAMixin):
     # === Borrowed from ScheduleBatch: host metadata (CPU lists / mirrors) ===
     # Optional seq_lens on cpu (CPU mirror of seq_lens)
     seq_lens_cpu: Optional[torch.Tensor] = None
+    # Fresh only for non-speculative extend; speculative modes use device slots.
+    req_pool_indices_cpu: Optional[torch.Tensor] = None
 
     # For logprob
     top_logprobs_nums: Optional[List[int]] = None
@@ -908,6 +910,11 @@ class ForwardBatch(ForwardBatchDeepSeekMHAMixin):
             seq_lens_sum=batch.seq_lens_sum,
             # Inputs aliased by reference from ScheduleBatch
             seq_lens_cpu=seq_lens_cpu,
+            req_pool_indices_cpu=(
+                getattr(batch, "req_pool_indices_cpu", None)
+                if batch.forward_mode.is_extend_without_speculative()
+                else None
+            ),
             orig_seq_lens=batch.orig_seq_lens,
             out_cache_loc_dsv4=batch.out_cache_loc_dsv4,
             engram_history=batch.engram_history,
@@ -1671,6 +1678,10 @@ class ForwardBatch(ForwardBatchDeepSeekMHAMixin):
             # Keep token-aligned inputs consistent after padding.
             self.input_embeds = self._pad_tensor_to_size(self.input_embeds, num_tokens)
         self.req_pool_indices = self._pad_tensor_to_size(self.req_pool_indices, bs)
+        if self.req_pool_indices_cpu is not None:
+            self.req_pool_indices_cpu = self._pad_tensor_to_size(
+                self.req_pool_indices_cpu, bs
+            )
         if self.lora_ids is not None:
             self.lora_ids.extend((bs - len(self.lora_ids)) * [None])
 
@@ -1836,6 +1847,8 @@ class ForwardBatch(ForwardBatchDeepSeekMHAMixin):
             self.positions = self.positions[: self._original_num_tokens]
             self.seq_lens = self.seq_lens[:bs]
             self.req_pool_indices = self.req_pool_indices[:bs]
+            if self.req_pool_indices_cpu is not None:
+                self.req_pool_indices_cpu = self.req_pool_indices_cpu[:bs]
             if self.seq_lens_cpu is not None:
                 self.seq_lens_cpu = self.seq_lens_cpu[:bs]
 
@@ -1845,6 +1858,8 @@ class ForwardBatch(ForwardBatchDeepSeekMHAMixin):
                 self.positions = self.positions[:num_tokens]
                 self.seq_lens = self.seq_lens[:bs]
                 self.req_pool_indices = self.req_pool_indices[:bs]
+                if self.req_pool_indices_cpu is not None:
+                    self.req_pool_indices_cpu = self.req_pool_indices_cpu[:bs]
                 if self.seq_lens_cpu is not None:
                     self.seq_lens_cpu = self.seq_lens_cpu[:bs]
                 if logits_output.next_token_logits is not None:

python/sglang/srt/model_executor/runner/prefill_cuda_graph_runner.py

@@ -1176,6 +1176,10 @@ class PrefillCudaGraphRunner(BaseCudaGraphRunner):
             padded_view.seq_lens = s["seq_lens"][:r]
             padded_view.seq_lens_cpu = self._full_cg_seq_lens_cpu
             padded_view.req_pool_indices = s["req_pool_indices"][:r]
+            if getattr(forward_batch, "req_pool_indices_cpu", None) is not None:
+                padded_view.req_pool_indices_cpu = padded_view._pad_tensor_to_size(
+                    forward_batch.req_pool_indices_cpu, r
+                )
             padded_view.extend_seq_lens = s["extend_seq_lens"][:r]
             padded_view.extend_prefix_lens = s["extend_prefix_lens"][:r]
             padded_view.max_seq_len_override = static_forward_batch.max_seq_len_override

test/registered/unit/layers/test_kpool_planner_cpu_mirror.py

@@ -0,0 +1,147 @@
+"""CPU coverage for KPool request-slot selection and paged query rows."""
+
+import unittest
+from types import SimpleNamespace
+from unittest.mock import patch
+
+import torch
+
+from sglang.srt.environ import envs
+from sglang.srt.layers.attention.dsa import kpool_plan
+from sglang.srt.layers.attention.dsa.dsa_topk_backend import TopkTransformMethod
+from sglang.test.ci.ci_register import register_cpu_ci
+
+register_cpu_ci(est_time=5, suite="base-a-test-cpu")
+
+
+class _NoDeviceReadTensor(torch.Tensor):
+    def tolist(self):
+        raise AssertionError("Reading device request slots would synchronize")
+
+
+def _batch(extend_lens=(3, 5), seq_lens=(5, 11), slots=(9, 2)):
+    indices = torch.tensor(slots, dtype=torch.int64)
+    return SimpleNamespace(
+        batch_size=len(slots),
+        extend_seq_lens_cpu=list(extend_lens),
+        seq_lens_cpu=torch.tensor(seq_lens, dtype=torch.int64),
+        seq_lens=torch.tensor(seq_lens, dtype=torch.int64),
+        req_pool_indices=indices.as_subclass(_NoDeviceReadTensor),
+        req_pool_indices_cpu=indices,
+    )
+
+
+def _expected_plan():
+    return kpool_plan._KPoolCpuPlan(
+        pool_batch_idx=[0, 1],
+        pool_req=[9, 2],
+        pool_pool_id=[0, 1],
+        pool_n_from_tail=[2, 2],
+        pool_chunk_src=[0, 3],
+        pool_tail_logical_base=[0, 4],
+        tail_req=[9, 2],
+        tail_dst_logical_start=[4, 8],
+        tail_chunk_src=[2, 5],
+        tail_n_write=[1, 3],
+        ragged_q_len=[3, 5],
+        ragged_pool_pages=[1, 1],
+        cu_pages_excl=[0, 1],
+        cu_q_len_excl=[0, 3],
+        total_pool_pages=2,
+    )
+
+
+class TestKPoolPlannerCpuMirror(unittest.TestCase):
+    def test_mirror_avoids_device_read_and_preserves_compression_rows(self):
+        for tensor_lengths in (False, True):
+            with self.subTest(tensor_lengths=tensor_lengths):
+                batch = _batch()
+                if tensor_lengths:
+                    batch.extend_seq_lens_cpu = torch.tensor(batch.extend_seq_lens_cpu)
+                plan = kpool_plan._kpool_cpu_plan(batch, 4, 64)
+                self.assertEqual(plan, _expected_plan())
+
+    def test_absent_or_none_mirror_uses_device_slots(self):
+        for absent in (False, True):
+            with self.subTest(absent=absent):
+                batch = _batch()
+                batch.req_pool_indices = batch.req_pool_indices_cpu
+                if absent:
+                    del batch.req_pool_indices_cpu
+                else:
+                    batch.req_pool_indices_cpu = None
+                plan = kpool_plan._kpool_cpu_plan(batch, 4, 64)
+                self.assertEqual(plan, _expected_plan())
+
+    def test_empty_mirror_needs_no_device_read(self):
+        plan = kpool_plan._kpool_cpu_plan(_batch((), (), ()), 4, 64)
+        self.assertEqual(plan, kpool_plan._KPoolCpuPlan())
+
+    def test_paged_query_rows_use_local_lengths_and_explicit_output_size(self):
+        batch = _batch()
+        cpu_plan = kpool_plan._kpool_cpu_plan(
+            batch,
+            4,
+            64,
+            local_extend_seq_lens_cpu=[1, 2],
+            local_seq_lens_cpu=[3, 8],
+        )
+        expected = _expected_plan()
+        expected.ragged_q_len = [1, 2]
+        expected.ragged_pool_pages = [0, 1]
+        expected.cu_pages_excl = [0, 0]
+        expected.cu_q_len_excl = [0, 1]
+        expected.total_pool_pages = 1
+        self.assertEqual(cpu_plan, expected)
+
+        original_tensor = torch.tensor
+
+        def cpu_tensor(*args, **kwargs):
+            kwargs.pop("pin_memory", None)
+            return original_tensor(*args, **kwargs)
+
+        page_table = torch.zeros(2, 4, dtype=torch.int32)
+        req_to_token = torch.zeros(10, 256, dtype=torch.int32)
+        seq_lens = torch.tensor([3, 7, 8], dtype=torch.int32)
+        local_slots = torch.tensor([9, 2], dtype=torch.int64)
+        with (
+            envs.SGLANG_DSA_FUSE_TOPK.override(True),
+            patch.object(torch, "tensor", side_effect=cpu_tensor),
+            patch.object(
+                torch, "repeat_interleave", wraps=torch.repeat_interleave
+            ) as repeat,
+            patch.object(
+                kpool_plan,
+                "kpool_build_ragged_layout",
+                return_value=(torch.empty(0), torch.empty(0), torch.empty(0)),
+            ),
+            patch.object(kpool_plan, "dsa_use_prefill_cp", return_value=False),
+            patch.object(kpool_plan, "_RAGGED_SCRATCH_K_U8", None),
+            patch.object(kpool_plan, "_RAGGED_SCRATCH_K_SCALE", None),
+            patch.object(
+                kpool_plan,
+                "get_req_to_token_pool",
+                return_value=SimpleNamespace(req_to_token=req_to_token),
+            ),
+        ):
+            plan = kpool_plan._kpool_plan_to_gpu(
+                cpu_plan,
+                batch,
+                page_table,
+                page_table,
+                seq_lens,
+                local_slots,
+                4,
+                64,
+                TopkTransformMethod.PAGED,
+            )
+
+        repeat.assert_called_once()
+        self.assertEqual(repeat.call_args.kwargs["output_size"], 3)
+        self.assertEqual(plan.ragged_paged_page_table_row_index.tolist(), [9, 2, 2])
+        self.assertEqual(plan.ragged_paged_page_table_row_index.dtype, torch.int32)
+        self.assertIs(plan.ragged_paged_page_table, req_to_token)
+
+
+if __name__ == "__main__":
+    unittest.main()

test/registered/unit/layers/test_kpool_stream_scheduling.py

@@ -0,0 +1,316 @@
+"""CPU scheduling checks: stream dependencies, cache contracts and gate math."""
+
+import unittest
+from contextlib import contextmanager, nullcontext
+from types import MethodType, SimpleNamespace
+from unittest.mock import Mock, patch
+
+import torch
+import torch.nn.functional as F
+
+from sglang.kernels.ops.attention.dsa import triton_kernel
+from sglang.srt.layers.attention.dsa import dsa_indexer_kpool as indexer_module
+from sglang.srt.layers.attention.dsa.dsa_indexer_kpool import IndexerKPool
+from sglang.srt.model_executor.forward_batch_info import ForwardMode
+from sglang.test.ci.ci_register import register_cpu_ci
+
+register_cpu_ci(est_time=5, suite="base-a-test-cpu")
+
+
+def _eager(method):
+    return getattr(method, "_torchdynamo_orig_callable", method)
+
+
+class _Stream:
+    def __init__(self, name, trace):
+        self.name = name
+        self.trace = trace
+
+    def wait_stream(self, other):
+        self.trace.append(("wait", self.name, other.name))
+
+
+class _Streams:
+    def __init__(self):
+        self.trace = []
+        self.current = _Stream("main", self.trace)
+        self.alt = _Stream("alt", self.trace)
+        self.gate = _Stream("gate", self.trace)
+
+    @contextmanager
+    def use(self, stream):
+        previous = self.current
+        self.current = stream
+        try:
+            yield
+        finally:
+            self.current = previous
+
+    def record(self, operation):
+        self.trace.append((operation, self.current.name))
+
+
+class TestKPoolStreamScheduling(unittest.TestCase):
+    def test_prefill_overlap_excludes_cp_and_graph_capture(self):
+        for mode in (ForwardMode.EXTEND, ForwardMode.DECODE, ForwardMode.TARGET_VERIFY):
+            for has_stream in (False, True):
+                for capture, breakable, cp in (
+                    (False, False, False),
+                    (True, False, False),
+                    (False, True, False),
+                    (False, False, True),
+                ):
+                    with (
+                        self.subTest(
+                            mode=mode,
+                            stream=has_stream,
+                            capture=capture,
+                            breakable=breakable,
+                            cp=cp,
+                        ),
+                        patch.object(
+                            indexer_module, "get_is_capture_mode", return_value=capture
+                        ),
+                        patch.object(
+                            indexer_module,
+                            "is_in_breakable_cuda_graph",
+                            return_value=breakable,
+                        ),
+                        patch.object(
+                            indexer_module, "dsa_use_prefill_cp", return_value=cp
+                        ),
+                    ):
+                        indexer = SimpleNamespace(
+                            alt_stream=object() if has_stream else None
+                        )
+                        actual = IndexerKPool._can_overlap_prefill(
+                            indexer,
+                            SimpleNamespace(forward_mode=mode),
+                            return_indices=True,
+                        )
+                        self.assertEqual(
+                            actual,
+                            mode == ForwardMode.EXTEND
+                            and has_stream
+                            and not (capture or breakable or cp),
+                        )
+
+    def test_precomputed_head_gate_matches_original_math(self):
+        torch.manual_seed(19)
+        for dtype in (torch.bfloat16, torch.float16, torch.float32):
+            x = torch.randn(11, 32).to(dtype)
+            matrix = torch.randn(8, 32)
+            q_scale = torch.rand(11, 8, 1)
+            indexer = SimpleNamespace(
+                weights_proj=lambda value: (F.linear(value, matrix), None),
+                n_heads=8,
+                softmax_scale=128**-0.5,
+            )
+            expected = _eager(IndexerKPool._get_logits_head_gate)(indexer, x, q_scale)
+            projected = _eager(IndexerKPool._project_and_scale_head_gates)(indexer, x)
+            actual = _eager(IndexerKPool._apply_q_scale_and_softmax_scale)(
+                indexer, projected, q_scale
+            )
+            torch.testing.assert_close(actual, expected, rtol=0, atol=0)
+
+    def test_projection_reordering_preserves_rope_and_third_stream(self):
+        for skip_rope in (False, True):
+            streams = _Streams()
+            x = torch.arange(32, dtype=torch.float32).reshape(4, 8)
+            indexer = SimpleNamespace(
+                alt_stream=streams.alt,
+                compress_gate_stream=streams.gate,
+                half_device_sm_count=8,
+                head_dim=4,
+                rope_head_dim=2,
+                skip_rope=skip_rope,
+                index_kpool_compress_gate=torch.ones(4, 8),
+            )
+
+            def project_q(value):
+                streams.record("project_q")
+                return value.clone(), None
+
+            def project_k(value):
+                streams.record("project_k")
+                return value[:, :4].clone(), None
+
+            def head_gate(value):
+                streams.record("head_gate")
+                return value[:, :2].clone()
+
+            def rotate(value):
+                streams.record("rotate")
+                return value.flip(-1)
+
+            def rope(positions, q, k):
+                streams.record("rope")
+                return q + 1, k + 2
+
+            indexer.wq_b = project_q
+            indexer.wk = project_k
+            indexer.k_norm = lambda value: value
+            indexer.rotary_emb = rope
+            indexer._project_and_scale_head_gates = head_gate
+            with (
+                patch.object(
+                    torch.cuda, "current_stream", side_effect=lambda: streams.current
+                ),
+                patch.object(torch.cuda, "stream", side_effect=streams.use),
+                patch.object(
+                    indexer_module.deep_gemm_wrapper,
+                    "configure_deep_gemm_num_sms",
+                    return_value=nullcontext(),
+                ),
+                patch.object(indexer_module, "rotate_activation", side_effect=rotate),
+            ):
+                actual = IndexerKPool._get_q_k_bf16(
+                    indexer,
+                    x,
+                    x,
+                    torch.arange(4),
+                    True,
+                    None,
+                    precompute_compress_gate=True,
+                    precompute_head_gate=True,
+                )
+                trace = streams.trace[:]
+                expected = IndexerKPool._get_q_k_bf16(
+                    indexer, x, x, torch.arange(4), False, None
+                )
+            torch.testing.assert_close(actual[0], expected[0])
+            torch.testing.assert_close(actual[1], expected[1])
+            torch.testing.assert_close(
+                actual[2], F.linear(x, indexer.index_kpool_compress_gate)
+            )
+            self.assertIsNotNone(actual[3])
+            self.assertIn(("wait", "gate", "main"), trace)
+            join = trace.index(("wait", "main", "alt"))
+            self.assertLess(trace.index(("head_gate", "main")), join)
+            if skip_rope:
+                self.assertLess(trace.index(("rotate", "main")), join)
+                self.assertNotIn(("rope", "main"), trace)
+            else:
+                self.assertGreater(trace.index(("rope", "main")), join)
+                self.assertGreater(trace.index(("rotate", "main")), join)
+
+    def test_prefill_waits_before_topk_and_preserves_deferred_cache(self):
+        for has_plan in (False, True):
+            for return_indices in (False, True):
+                for cp in (False, True):
+                    for num_tokens in (0, 128, 8192):
+                        with self.subTest(
+                            plan=has_plan,
+                            indices=return_indices,
+                            cp=cp,
+                            tokens=num_tokens,
+                        ):
+                            self._run_prefill(has_plan, return_indices, cp, num_tokens)
+
+    def _run_prefill(self, has_plan, return_indices, cp, num_tokens):
+        streams = _Streams()
+        x = torch.ones(num_tokens, 8)
+        compressed = object()
+        calls = []
+        metadata = SimpleNamespace(
+            attn_metadata=SimpleNamespace(
+                kpool_extend_plan=object() if has_plan else None
+            )
+        )
+        batch = SimpleNamespace(
+            forward_mode=ForwardMode.EXTEND,
+            seq_lens_cpu=torch.tensor([8192 + num_tokens]),
+        )
+        prepare_qk = Mock(return_value=(x, x, None, None))
+        indexer = SimpleNamespace(
+            alt_stream=streams.alt,
+            compress_gate_stream=streams.gate,
+            index_topk=16,
+            index_kpool=4,
+            index_kpool_compress=True,
+            block_size=128,
+            scale_fmt=None,
+            _get_q_k_bf16=prepare_qk,
+        )
+        indexer._can_overlap_prefill = MethodType(
+            IndexerKPool._can_overlap_prefill, indexer
+        )
+
+        def compress(**kwargs):
+            streams.record("compress")
+            calls.append(kwargs)
+            return compressed
+
+        def quant(*args):
+            streams.record("quant")
+            return x, torch.ones(num_tokens, 1, 1)
+
+        def head(*args):
+            streams.record("head")
+            return x
+
+        def topk(*args, **kwargs):
+            streams.record("topk")
+            if not has_plan:
+                self.assertIs(kwargs["kpool_extend_cache"], compressed)
+            return x
+
+        indexer._compress_write = compress
+        indexer._resolve_head_gate_weights = head
+        indexer._get_topk_ragged = topk
+        indexer._get_topk_ragged_kpool_plan = topk
+        with (
+            patch.object(indexer_module, "is_cuda", return_value=True),
+            patch.object(indexer_module, "is_hip", return_value=False),
+            patch.object(indexer_module, "is_npu", return_value=False),
+            patch.object(indexer_module, "get_is_capture_mode", return_value=False),
+            patch.object(
+                indexer_module, "is_in_breakable_cuda_graph", return_value=False
+            ),
+            patch.object(indexer_module, "dsa_use_prefill_cp", return_value=cp),
+            patch.object(
+                indexer_module,
+                "get_attn_backend",
+                return_value=SimpleNamespace(
+                    get_indexer_metadata=lambda *args: metadata
+                ),
+            ),
+            patch.object(
+                torch.cuda, "current_stream", side_effect=lambda: streams.current
+            ),
+            patch.object(torch.cuda, "stream", side_effect=streams.use),
+            patch.object(triton_kernel, "act_quant", side_effect=quant),
+        ):
+            actual = IndexerKPool._forward_cuda_impl(
+                indexer, x, x, torch.arange(num_tokens), batch, 0, return_indices
+            )
+        self.assertEqual(calls[0]["return_compressed"], return_indices)
+        self.assertEqual(calls[0]["write_cache"], has_plan or not return_indices)
+        self.assertFalse(prepare_qk.call_args.args[3])
+        self.assertFalse(prepare_qk.call_args.kwargs["precompute_head_gate"])
+        overlap = not cp and return_indices
+        self.assertIn(("compress", "alt" if overlap else "main"), streams.trace)
+        if overlap:
+            self.assertLess(
+                streams.trace.index(("wait", "alt", "main")),
+                streams.trace.index(("compress", "alt")),
+            )
+            join = streams.trace.index(("wait", "main", "alt"))
+            self.assertGreater(join, streams.trace.index(("compress", "alt")))
+            self.assertGreater(join, streams.trace.index(("quant", "main")))
+            self.assertGreater(join, streams.trace.index(("head", "main")))
+            self.assertLess(join, streams.trace.index(("topk", "main")))
+        else:
+            self.assertFalse(any(event[0] == "wait" for event in streams.trace))
+        if return_indices:
+            self.assertIs(actual, x)
+            self.assertIn(("quant", "main"), streams.trace)
+        else:
+            self.assertIsNone(actual)
+            self.assertNotIn(("quant", "main"), streams.trace)
+            self.assertNotIn(("head", "main"), streams.trace)
+            self.assertNotIn(("topk", "main"), streams.trace)
+
+
+if __name__ == "__main__":
+    unittest.main()

test/registered/unit/model_executor/runner/test_prefill_cuda_graph_padding.py

@@ -10,6 +10,7 @@ from sglang.srt.model_executor import forward_batch_info
 from sglang.srt.model_executor.cuda_graph_config import Backend
 from sglang.srt.model_executor.forward_batch_info import (
     CaptureHiddenMode,
+    ForwardBatch,
     ForwardMode,
     prefill_graph_tolerates_sum_len,
 )
@@ -93,6 +94,62 @@ class TestPrefillCudaGraphPadding(CustomTestCase):
             forward_batch, num_qo_tokens=16
         )
 
+    def test_full_replay_pads_request_slot_cpu_mirror(self):
+        for batch_size, has_mirror in ((2, True), (4, True), (2, False)):
+            with self.subTest(batch_size=batch_size, has_mirror=has_mirror):
+                runner = self._make_runner()
+                runner._is_full_backend = True
+                runner._capture_req_slots = 4
+                runner._full_cg_seq_lens_cpu = torch.full((4,), -1)
+                slots = torch.tensor([7, 2, 9, 5])[:batch_size]
+                seq_lens = torch.arange(1, batch_size + 1)
+                static_slots = torch.zeros(4, dtype=slots.dtype)
+                static_slots[:batch_size].copy_(slots)
+                static_lens = torch.zeros(4, dtype=seq_lens.dtype)
+                static_lens[:batch_size].copy_(seq_lens)
+                runner._prefill_static_buffers = {
+                    "req_pool_indices": static_slots,
+                    "seq_lens": static_lens,
+                    "extend_seq_lens": static_lens.clone(),
+                    "extend_prefix_lens": torch.zeros(4, dtype=torch.int64),
+                }
+                attn_backend = mock.Mock()
+                runner.model_runner = SimpleNamespace(attn_backend=attn_backend)
+                batch = ForwardBatch(
+                    forward_mode=ForwardMode.EXTEND,
+                    batch_size=batch_size,
+                    input_ids=torch.arange(batch_size),
+                    req_pool_indices=slots,
+                    req_pool_indices_cpu=slots if has_mirror else None,
+                    seq_lens=seq_lens,
+                    seq_lens_cpu=seq_lens,
+                    out_cache_loc=torch.arange(batch_size),
+                    seq_lens_sum=int(seq_lens.sum()),
+                )
+
+                runner._prepare_forward_metadata_for_replay(
+                    batch, batch, shape_key=ShapeKey(size=16)
+                )
+
+                attn_backend.init_forward_metadata_out_graph.assert_called_once()
+                padded = attn_backend.init_forward_metadata_out_graph.call_args.args[0]
+                self.assertIsInstance(padded, ForwardBatch)
+                self.assertIsNot(padded, batch)
+                self.assertEqual(padded.batch_size, 4)
+                torch.testing.assert_close(padded.seq_lens_cpu, static_lens)
+                torch.testing.assert_close(padded.req_pool_indices, static_slots)
+                if has_mirror:
+                    torch.testing.assert_close(
+                        padded.req_pool_indices_cpu, static_slots
+                    )
+                    self.assertEqual(padded.req_pool_indices_cpu.device.type, "cpu")
+                    self.assertIs(batch.req_pool_indices_cpu, slots)
+                else:
+                    self.assertIsNone(padded.req_pool_indices_cpu)
+                self.assertEqual(batch.batch_size, batch_size)
+                torch.testing.assert_close(batch.seq_lens_cpu, seq_lens)
+                attn_backend.init_forward_metadata.assert_not_called()
+
     def _megamoe_no_prefill_cp(self, graph_has_dp_gather=False):
         return (
             mock.patch.object(