[Example] Optimize sink attention forward via swizzled layout and report benchmark results (#885)

* Enhance attention sink examples with swizzled layout and performance metrics

- Added `make_swizzled_layout` annotations for shared tensors in the `flashattn` function across MHA and GQA examples to optimize memory access patterns.
- Updated benchmark outputs to include speedup calculations comparing Triton and TileLang implementations.

* Add README for Attention Sink example with algorithm details and benchmark results

- Introduced a new README.md file for the Attention Sink example, outlining the forward and backward algorithms, including the computation of `dsinks`.
- Provided benchmark results comparing performance metrics of the optimized implementation against Triton, highlighting speedup across various configurations.

* Update README.md for Attention Sink example to include link to Triton implementation

* Update examples/attention_sink/README.md
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

* Update examples/attention_sink/example_gqa_sink_fwd_bhsd_wgmma_pipelined.py
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

* typo

---------
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

examples/attention_sink/README.md

+# Attention Sink
+
+We compare with an optimized version of the official Triton implementation at [here](https://github.com/openai/gpt-oss/blob/main/gpt_oss/triton/attention.py).
+
+
+## Algorithm
+### Forward
+The only change from vanilla FlashAttention is that `sinks` should be taken into consideration in the softmax, which requires an extra rescaling at the epilogue stage.
+
+### Backward
+Based on detailed mathematical derivation, interestingly, the backward computation process of `dQ`, `dK`, `dv` is almost identical to that in vanilla FlashAttention, except for that the specific meanings of `lse` differ. We only need to compute `dsinks` additionally, which is given by:
+
+$$
+dsink_h=-\sum_{b}\sum_{q}P_{b, h, q}Delta_{b, h, q}
+$$
+
+where $P_{b, h, q}$ is the proportion of $sink_h$ in the softmax in the $b$-th block, $h$-th head and $q$-th query(row).
+
+## Benchmark of forward process
+
+### Benchmark Environment
+- **Hardware**: NVIDIA H800
+- **CUDA version**: 12.9
+- **Triton Version**: 3.4.0
+
+### Results
+
+- dtype=float16
+- batch_size=1, heads=64, kv_heads=8 (the setting of GPT-OSS-120B)
+- Full attention is adopted.
+
+| SEQ_LEN | headdim | Triton TFLOPs | TileLang TFLOPs      | Speedup |
+|---------|---------|---------------|----------------------|---------|
+| 2048    |   64    | 231.55        | **277.07**           | 1.20x   |
+| 2048    |  128    | 313.55        | **393.98**           | 1.26x   |
+|         |         |               |                      |         |
+| 4096    |   64    | 272.17        | **337.30**           | 1.24x   |
+| 4096    |  128    | 356.35        | **461.54**           | 1.30x   |
+|         |         |               |                      |         |
+| 8192    |   64    | 289.93        | **353.81**           | 1.22x   |
+| 8192    |  128    | 392.18        | **482.50**           | 1.23x   |
+|         |         |               |                      |         |
+| 16384   |   64    | 299.52        | **377.44**           | 1.26x   |
+| 16384   |  128    | 404.64        | **519.02**           | 1.28x   |
+
+> The backward performance will be further optimized via fine-grained manual pipelining of FA3 in the tilelang kernel.
\ No newline at end of file

examples/attention_sink/example_gqa_sink_fwd_bhsd_wgmma_pipelined.py

@@ -6,6 +6,7 @@ import tilelang
 from tilelang.autotuner import autotune
 from tilelang.profiler import do_bench
 import tilelang.language as T
+from tilelang.layout import make_swizzled_layout
 import itertools
 import argparse
 import triton
@@ -152,6 +153,13 @@ def flashattn(
             logsum = T.alloc_fragment([block_M], accum_dtype)
             sinks = T.alloc_fragment([block_M], dtype)
 
+            T.annotate_layout({
+                Q_shared: make_swizzled_layout(Q_shared),
+                K_shared: make_swizzled_layout(K_shared),
+                V_shared: make_swizzled_layout(V_shared),
+                O_shared: make_swizzled_layout(O_shared),
+            })
+
             T.copy(Q[bz, by, bx * block_M:(bx + 1) * block_M, :], Q_shared)
             T.fill(acc_o, 0)
             T.fill(logsum, 0)
@@ -425,22 +433,24 @@ def main(
             print("Checks for triton failed.❌")
 
         # Benchmark triton
-        latency = do_bench(lambda: triton_program(Q, K, V, sinks, window_size), warmup=500)
-        print("Triton: {:.2f} ms".format(latency))
-        print("Triton: {:.2f} TFlops".format(total_flops / latency * 1e-9))
+        latency_triton = do_bench(lambda: triton_program(Q, K, V, sinks, window_size), warmup=500)
+        print("Triton: {:.2f} ms".format(latency_triton))
+        print("Triton: {:.2f} TFlops".format(total_flops / latency_triton * 1e-9))
 
         # Benchmark tilelang
-        latency = do_bench(lambda: kernel(Q, K, V, sinks), warmup=500)
-        print("Tilelang: {:.2f} ms".format(latency))
-        print("Tilelang: {:.2f} TFlops".format(total_flops / latency * 1e-9))
+        latency_tilelang = do_bench(lambda: kernel(Q, K, V, sinks), warmup=500)
+        print("Tilelang: {:.2f} ms".format(latency_tilelang))
+        print("Tilelang: {:.2f} TFlops".format(total_flops / latency_tilelang * 1e-9))
+
+        print("Speedup: {:.2f}x".format(latency_triton / latency_tilelang))
 
 
 if __name__ == "__main__":
     parser = argparse.ArgumentParser()
     parser.add_argument('--batch', type=int, default=1, help='batch size')
     parser.add_argument('--heads', type=int, default=64, help='heads')
-    parser.add_argument('--seq_q', type=int, default=4096, help='sequence length of query')
-    parser.add_argument('--seq_kv', type=int, default=4096, help='sequence length of key/value')
+    parser.add_argument('--seq_q', type=int, default=2048, help='sequence length of query')
+    parser.add_argument('--seq_kv', type=int, default=2048, help='sequence length of key/value')
     parser.add_argument('--dim', type=int, default=128, help='dim')
     parser.add_argument('--groups', type=int, default=8, help='groups')
     parser.add_argument(

examples/attention_sink/example_mha_sink_fwd_bhsd.py

@@ -5,6 +5,7 @@ import tilelang
 from tilelang.autotuner import autotune
 from tilelang.profiler import do_bench
 import tilelang.language as T
+from tilelang.layout import make_swizzled_layout
 import itertools
 import argparse
 
@@ -140,6 +141,13 @@ def flashattn(
             logsum = T.alloc_fragment([block_M], accum_dtype)
             sinks = T.alloc_fragment([block_M], dtype)
 
+            T.annotate_layout({
+                Q_shared: make_swizzled_layout(Q_shared),
+                K_shared: make_swizzled_layout(K_shared),
+                V_shared: make_swizzled_layout(V_shared),
+                O_shared: make_swizzled_layout(O_shared),
+            })
+
             T.copy(Q[bz, by, bx * block_M:(bx + 1) * block_M, :], Q_shared)
             T.fill(acc_o, 0)
             T.fill(logsum, 0)

examples/attention_sink/example_mha_sink_fwd_bhsd_wgmma_pipelined.py

@@ -6,6 +6,7 @@ import tilelang
 from tilelang.autotuner import autotune
 from tilelang.profiler import do_bench
 import tilelang.language as T
+from tilelang.layout import make_swizzled_layout
 import itertools
 import argparse
 import triton
@@ -145,6 +146,13 @@ def flashattn(
             logsum = T.alloc_fragment([block_M], accum_dtype)
             sinks = T.alloc_fragment([block_M], dtype)
 
+            T.annotate_layout({
+                Q_shared: make_swizzled_layout(Q_shared),
+                K_shared: make_swizzled_layout(K_shared),
+                V_shared: make_swizzled_layout(V_shared),
+                O_shared: make_swizzled_layout(O_shared),
+            })
+
             T.copy(Q[bz, by, bx * block_M:(bx + 1) * block_M, :], Q_shared)
             T.fill(acc_o, 0)
             T.fill(logsum, 0)