metal : per-device tuned (Q, NE) for flash-attn vec (#26570)

* metal : per-device tuned (Q, NE) for flash-attn vec (#25750)

* rebase Q-generic FA vec body from 01dc93607 (#23114)

* add 53 f16 (Q,NE) flash-attn vec instantiations (vec 80 -> 133)

* add FA vec (Q,NE) tuning table + dispatch wiring + SMEM cap fallback

* add  FA vec (Q,NE) perf sweep

* fill tuning result

* fold family table into a per-family representative SKU

* refactor tuning result format

* extend FA vec tuning to quantized KV caches

* sync fa vec tuner bucketing with runtime, use pointwise tuning regret

* update tuned table

* format and cleanup

* prefix fa_vec tuning procs with ggml_backend_metal_tuning_, drop unused fa_vec_override_active

* add device id -> token lookup for the offline tuning tool

* add ggml-metal-tuning skeleton

* add op-agnostic perf cell + median timing for the tuner

* add FA-vec graph build + tensor init to the tuner

* tools : add FA-vec (Q,NE) sweep, compression and table emit

* cool down and re-measure the dirty window on thermal drift

* test-backend-ops : replace the FA vec tune mode with a bounded (Q,NE) slice

* tools : document the Metal tuner, point the table comment at it

* abort on unknown KV type, single-source fa_vec_legal_ne

* cleanup

* honor -o in the FA vec (Q,NE) slice

* retune FA-vec (Q, NE) under a pointwise no-harm gate

* cont : add fa-vec tunings for M1 Pro, M2 Ultra, M5 Max

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

ggml/src/ggml-metal/ggml-metal-ops.cpp

@@ -7,6 +7,7 @@
 #include "ggml-metal-impl.h"
 #include "ggml-metal-common.h"
 #include "ggml-metal-device.h"
+#include "ggml-metal-tuning.h"
 
 #include <cassert>
 #include <algorithm>
@@ -3346,12 +3347,18 @@ int ggml_metal_op_flash_attn_ext(ggml_metal_op_t ctx, int idx) {
 #undef FATTN_SMEM
     } else {
         // half4x4 kernel
-        const int nqptg = OP_FLASH_ATTN_EXT_VEC_NQPSG; // queries per threadgroup
+        auto cfg = ggml_metal_tuning::fa_vec_pick(
+                props_dev->device_id,
+                props_dev->gpu_family,
+                (int) op->src[1]->type,
+                (int) ne00, (int) ne20,   // dk, dv (ne00 == dk for FA)
+                ne11, ne01);
+        int nqptg = cfg.Q;                             // queries per threadgroup
         const int ncpsg = OP_FLASH_ATTN_EXT_VEC_NCPSG; // cache values per simdgroup !! sync with kernel template arguments !!
         const int nhptg = 1;                           // heads per threadgroup
 
         GGML_ASSERT(nqptg <= 32);
-        GGML_ASSERT(nqptg  % 1  == 0);
+        GGML_ASSERT(nqptg == 1 || nqptg == 2 || nqptg == 4);  // only instantiated Q values
         GGML_ASSERT(ncpsg  % 32 == 0);
 
         bool need_sync = false;
@@ -3410,7 +3417,7 @@ int ggml_metal_op_flash_attn_ext(ggml_metal_op_t ctx, int idx) {
         // ne20*(nsg)
         // each simdgroup has a full f32 head vector in shared mem to accumulate results
         //
-#define FATTN_SMEM(nsg) (GGML_PAD(((GGML_PAD(ne00, 128) + 4*ncpsg + 2*GGML_PAD(ne20, 128))*(nsg))*(sizeof(float)/2), 16))
+#define FATTN_SMEM(nsg) (GGML_PAD(((GGML_PAD(ne00, 128) + 4*ncpsg + 2*GGML_PAD(ne20, 128))*(nsg)*nqptg)*(sizeof(float)/2), 16))
 
         int64_t nsg = 1;
 
@@ -3430,6 +3437,12 @@ int ggml_metal_op_flash_attn_ext(ggml_metal_op_t ctx, int idx) {
             }
         }
 
+        // fall back to baseline (Q=1) if the tuned config exceeds threadgroup memory
+        if ((size_t) FATTN_SMEM(nsg) > props_dev->max_theadgroup_memory_size) {
+            cfg   = ggml_metal_tuning::fa_vec_baseline_cfg((int) ne00, (int) ne20);
+            nqptg = cfg.Q;  // = 1
+        }
+
         const int32_t ns10 = nb11_attn/nb10_attn;
         const int32_t ns20 = nb21_attn/nb20_attn;
 
@@ -3468,7 +3481,7 @@ int ggml_metal_op_flash_attn_ext(ggml_metal_op_t ctx, int idx) {
             /*.logit_softcap =*/ logit_softcap,
         };
 
-        auto pipeline = ggml_metal_library_get_pipeline_flash_attn_ext_vec(lib, op, has_mask, has_sinks, has_bias, has_scap, has_kvpad, nsg, nwg, use_kv_f16, ns10, ns20);
+        auto pipeline = ggml_metal_library_get_pipeline_flash_attn_ext_vec(lib, op, has_mask, has_sinks, has_bias, has_scap, has_kvpad, nqptg, cfg.NE, nsg, nwg, use_kv_f16, ns10, ns20);
 
         GGML_ASSERT(nsg*32 <= ggml_metal_pipeline_max_theads_per_threadgroup(pipeline));