Set kHasUnevenSplits=false if num_splits = 1

example/ck_tile/01_fmha/codegen/ops/fmha_fwd_splitkv.py

@@ -47,7 +47,7 @@ using fmha_dtype_{F_idx} = {F_dtype};
 using fmha_mask_{F_idx} = {F_mask};
 
 namespace {{
-template <bool kHasUnevenSplits, bool kIsMultipleSplits>
+template <bool kIsMultipleSplits, bool kHasUnevenSplits = kIsMultipleSplits>
 struct kernel_runner {{
 using fmha_block_tile = ck_tile::sequence<{F_bm0}, {F_bn0}, {F_bk0}, {F_bn1}, {F_bk1}, {F_bk0max}>;
 using fmha_warp_tile = ck_tile::sequence<{F_wm}, {F_wn}, {F_wk}>;
@@ -68,7 +68,7 @@ using fmha_trait = ck_tile::TileFmhaFwdSplitKVTraits<{F_spad},
                                                      {F_lse},
                                                      {F_squant},
                                                      {F_pagedkv},
-                                                     kHasUnevenSplits,
+                                                     kIsMultipleSplits && kHasUnevenSplits,
                                                      {F_occupancy}>;
 
 using fmha_pipeline_problem = ck_tile::BlockFmhaFwdSplitKVPipelineProblem<
@@ -131,12 +131,23 @@ using trait_{F_idx} = fmha_fwd_splitkv_traits_<{F_hdim}, {F_dtype}, {F_mode}, {F
 template<>
 void fmha_fwd_splitkv_oneshot_<trait_{F_idx}>(const ck_tile::stream_config& s, fmha_fwd_splitkv_args a)
 {{
-    /// NOTICE: kHasUnevenSplits=false may be able to speed-up the batch mode kernel, 
-    ///         but we use kHasUnevenSplits=true here to reduce compilation time  
     if (1 < a.num_splits) {{
-        kernel_runner</*kHasUnevenSplits=*/true, /*kIsMultipleSplits=*/true>::run(s, a);
+        constexpr bool kIsMultipleSplits = true;
+        if constexpr({F_mode} == false) {{ // batch mode
+            // we don't check every seqlen_k values for kvcache
+            if (a.seqlen_k_ptr != nullptr) {{
+                kernel_runner<kIsMultipleSplits, /*kHasUnevenSplits=*/true>::run(s, a);
+            // make sure F_bn0 is divisible by F_bk1
+            }} else if (a.seqlen_k % (a.num_splits * {F_bn0}) == 0) {{
+                kernel_runner<kIsMultipleSplits, /*kHasUnevenSplits=*/false>::run(s, a);
             }} else {{
-        kernel_runner</*kHasUnevenSplits=*/true, /*kIsMultipleSplits=*/false>::run(s, a);
+                kernel_runner<kIsMultipleSplits, /*kHasUnevenSplits=*/true>::run(s, a);
+            }}
+        }} else {{ // group mode
+            kernel_runner<kIsMultipleSplits, /*kHasUnevenSplits=*/true>::run(s, a);
+        }}
+    }} else {{
+        kernel_runner</*kIsMultipleSplits=*/false>::run(s, a);
     }}
 }}
 
@@ -659,7 +670,6 @@ def get_fwd_splitkv_blobs(kernel_filter : Optional[str], receipt, mask_impl) ->
             for mask, bias, lse, pagedkv in itertools.product(get_mask_map(mask_impl).keys(), BIAS_MAP.keys(), ["t", "f"], ["t", "f"]):
                 # TODO: use async pipeline when compiler is more stable
                 if hdim == 256 or hdim in [32, 64, 128]:         ### [32, 64, 96, 128]:
-                # if True:
                     pipelines.append(Pipeline('qr', 'row', 'f', 't', 'f', 'f', bias, lse, squant, pagedkv, mask))
                     pipelines.append(Pipeline('qr', 'col', 'f', 't', 'f', 'f', bias, lse, squant, pagedkv, mask))