[PP] Fix dynamic chunking strategy for PP (#15372)

Signed-off-by: Shangming Cai <csmthu@gmail.com>

python/sglang/srt/managers/scheduler_pp_mixin.py

@@ -10,6 +10,7 @@ from typing import TYPE_CHECKING, Dict, List, Optional, Tuple
 import numpy as np
 import torch
 import torch.distributed
+from tqdm import tqdm
 
 from sglang.srt.disaggregation.base.conn import KVPoll
 from sglang.srt.disaggregation.utils import DisaggregationMode, poll_and_all_reduce
@@ -532,13 +533,11 @@ class SchedulerPPMixin:
         latencies: List[float] = []
 
         if self.pp_group.is_first_rank:
-            logger.info("Profiling prefill latency for dynamic chunk sizing...")
-
-            # Create requests with different lengths: base_chunk_size // (2**i) for i in range(10)
             input_ids_list = []
-            for i in range(32):
+            for i in range(128):
-                chunk_size = self.chunked_prefill_size - i * (
+                chunk_size = int(
-                    self.chunked_prefill_size // 32
+                    self.chunked_prefill_size * 1.25
+                    - i * (self.chunked_prefill_size * 1.25 // 128)
                 )
                 if chunk_size <= 0:
                     break
@@ -551,9 +550,13 @@ class SchedulerPPMixin:
                 temperature=0,
                 max_new_tokens=1,
             )
-
             # Create and profile requests
-            for i, input_ids in enumerate(input_ids_list):
+            for i, input_ids in enumerate(
+                tqdm(
+                    input_ids_list,
+                    desc="Profiling prefill latency for dynamic chunking",
+                )
+            ):
                 req = Req(
                     rid=str(i),
                     origin_input_text="",
@@ -1338,8 +1341,8 @@ class ChunkSizePredictor:
         )
         calculated_chunk_size = int(smoothed_chunk_size)
 
-        # Align to page_size (round down to nearest multiple)
+        # Align to page_size (minimum alignment size is 64)
-        alignment_size = max(page_size, 1)
+        alignment_size = max(page_size, 64)
         dynamic_chunk_size = (calculated_chunk_size // alignment_size) * alignment_size
 
         # Ensure aligned size is at least alignment_size