Refactor Matmul to use a policy class for parallelization.

PiperOrigin-RevId: 800864489

gemma/weights.cc

@@ -320,8 +320,6 @@ static void AllocateAndBindAll(std::vector<TensorToRead>& tensors,
   const size_t start = owners.size();
   owners.resize(start + tensors.size());
 
-  MMParallel parallel(ctx);
-
   // Allocate in parallel because faulting in large tensors is slow.
   ctx.pools.Pool().Run(
       0, tensors.size(), [&](uint64_t task, size_t /*thread*/) {
@@ -339,7 +337,7 @@ static void AllocateAndBindAll(std::vector<TensorToRead>& tensors,
 
         owners[start + task].AllocateFor(*tensor.mat, ctx.allocator,
                                          tensor.padding);
-        BindB(*tensor.mat, tensor.mat->ElementBytes(), parallel);
+        BindB(ctx, *tensor.mat, tensor.mat->ElementBytes());
       });
 }
 

ops/matmul-inl.h

@@ -779,17 +779,19 @@ class MMPerPackage {
   // B and maybe A are decompressed several call layers lower, but not all
   // member functions depend on TA/TB, so pass them as an argument instead of
   // templating the class.
-  template <typename TA, typename TB, typename TC>
+  template <typename TA, typename TB, typename TC, class MMParallelPolicyT>
-  HWY_NOINLINE void operator()(const MatPtrT<TA>& A, const MatPtrT<TB>& B,
+  HWY_NOINLINE void operator()(const MMParallelPolicyT& parallel_policy,
+                               const MatPtrT<TA>& A, const MatPtrT<TB>& B,
                                RowPtrs<TC> C_rows) const {
     if constexpr (WantDecompressA<TA>()) {
       const StridedViewBF A_view = args_.env->storage.A(pkg_idx_, A.Extents());
-      DecompressA(A, A_view);
+      DecompressA<MMParallelPolicyT>(A, A_view);
       constexpr bool A_padded = true;  // MMStorage `pkg_A_` is padded.
-      DispatchOrder(A_view, A_padded, B, C_rows);
+      DispatchOrder(parallel_policy, A_view, A_padded, B, C_rows);
     } else {
       const bool A_padded = HasPadding(A);
-      DispatchOrder(View(A, 0, 0, A.Cols()), A_padded, B, C_rows);
+      DispatchOrder(parallel_policy, View(A, 0, 0, A.Cols()), A_padded, B,
+                    C_rows);
     }
   }
 
@@ -828,28 +830,30 @@ class MMPerPackage {
   }
 
   // `TA` is usually BF16, but can be F32 if `!HWY_NATIVE_DOT_BF16`.
-  template <typename TA, typename TB, typename TC>
+  template <typename TA, typename TB, typename TC, class MMParallelPolicyT>
-  HWY_INLINE void DispatchOrder(const StridedView<TA> A, const bool A_padded,
+  HWY_INLINE void DispatchOrder(const MMParallelPolicyT& parallel_policy,
+                                const StridedView<TA> A, const bool A_padded,
                                 const MatPtrT<TB>& B,
                                 RowPtrs<TC> C_rows) const {
     switch (order_) {
       case MMOrder::kNT:
-        return DoNT(A, A_padded, B, C_rows);
+        return DoNT<TA, TB, TC>(parallel_policy, A, A_padded, B, C_rows);
       case MMOrder::kNT_K:
-        return DoNT_K(A, A_padded, B, C_rows);
+        return DoNT_K<TA, TB, TC>(parallel_policy, A, A_padded, B, C_rows);
       case MMOrder::kNT_MT:
-        return DoNT_MT(A, A_padded, B, C_rows);
+        return DoNT_MT<TA, TB, TC>(parallel_policy, A, A_padded, B, C_rows);
       case MMOrder::kNT_MT_K:
-        return DoNT_MT_K(A, A_padded, B, C_rows);
+        return DoNT_MT_K<TA, TB, TC>(parallel_policy, A, A_padded, B, C_rows);
       default:
         HWY_UNREACHABLE;
     }
   }
 
   // Single M and K ranges, parallel N. Fills all of C directly.
-  template <typename TA, typename TB, typename TC>
+  template <typename TA, typename TB, typename TC, class MMParallelPolicyT>
-  HWY_INLINE void DoNT(const StridedView<TA> A, const bool A_padded,
+  HWY_INLINE void DoNT(MMParallelPolicyT, const StridedView<TA> A,
-                       const MatPtrT<TB>& B, RowPtrs<TC> C_rows) const {
+                       const bool A_padded, const MatPtrT<TB>& B,
+                       RowPtrs<TC> C_rows) const {
     static const auto zone = args_.env->ctx.profiler.AddZone("MM.NT");
     HWY_DASSERT(ranges_mc_.NumTasks() == 1);
     HWY_DASSERT(ranges_kc_.NumTasks() == 1);
@@ -861,9 +865,9 @@ class MMPerPackage {
         Stride(MatPadding::kOdd, K, sizeof(BF16), line_bytes_);
 
     // Similar to `loop_nc` below, but here we hoisted `A_view`.
-    args_.env->parallel.ForNP(
+    MMParallelPolicyT::ForNP(
-        range_np_, MultipleNP(sizeof(TC)), inner_tasks_, pkg_idx_,
+        args_.env->ctx, range_np_, MultipleNP(sizeof(TC)), inner_tasks_,
-        [&](const IndexRange& range_nc, size_t worker) HWY_ATTR {
+        pkg_idx_, [&](const IndexRange& range_nc, size_t worker) HWY_ATTR {
           MMZone mm_zone;
           mm_zone.MaybeEnter(worker, zone, args_);
 
@@ -881,9 +885,10 @@ class MMPerPackage {
   }
 
   // Single M range, parallel N, sequential K. Sets C, then accumulates.
-  template <typename TA, typename TB, typename TC>
+  template <typename TA, typename TB, typename TC, class MMParallelPolicyT>
-  HWY_INLINE void DoNT_K(const StridedView<TA> A, const bool A_padded,
+  HWY_INLINE void DoNT_K(MMParallelPolicyT, const StridedView<TA> A,
-                         const MatPtrT<TB>& B, RowPtrs<TC> C_rows) const {
+                         const bool A_padded, const MatPtrT<TB>& B,
+                         RowPtrs<TC> C_rows) const {
     static const auto zone = args_.env->ctx.profiler.AddZone("MM.NT_K");
     HWY_DASSERT(ranges_mc_.NumTasks() == 1);
     const IndexRange& range_mc = ranges_mc_.Range(0);
@@ -909,9 +914,9 @@ class MMPerPackage {
       }
     };
 
-    args_.env->parallel.ForNP(
+    MMParallelPolicyT::ForNP(
-        range_np_, MultipleNP(sizeof(TC)), inner_tasks_, pkg_idx_,
+        args_.env->ctx, range_np_, MultipleNP(sizeof(TC)), inner_tasks_,
-        [&](const IndexRange& range_nc, size_t worker) HWY_ATTR {
+        pkg_idx_, [&](const IndexRange& range_nc, size_t worker) HWY_ATTR {
           MMZone mm_zone;
           mm_zone.MaybeEnter(worker, zone, args_);
 
@@ -930,9 +935,10 @@ class MMPerPackage {
 
   // Parallel loops over mc/nc blocks of M/range_np, single K.
   // Fills `mc x nc` sections of C directly, in parallel.
-  template <typename TA, typename TB, typename TC>
+  template <typename TA, typename TB, typename TC, class MMParallelPolicyT>
-  HWY_INLINE void DoNT_MT(const StridedView<TA> A, const bool A_padded,
+  HWY_INLINE void DoNT_MT(MMParallelPolicyT, const StridedView<TA> A,
-                          const MatPtrT<TB>& B, RowPtrs<TC> C_rows) const {
+                          const bool A_padded, const MatPtrT<TB>& B,
+                          RowPtrs<TC> C_rows) const {
     static const auto zone = args_.env->ctx.profiler.AddZone("MM.NT_MT");
     HWY_DASSERT(ranges_kc_.NumTasks() == 1);
     const IndexRange& range_K = ranges_kc_.Range(0);
@@ -942,8 +948,8 @@ class MMPerPackage {
 
     // Sequential loop over NC/MC/KC, similar to `loop_nc` below
     // except for the profiler strings and `out_tag`.
-    args_.env->parallel.ForRangesMC_NC(
+    MMParallelPolicyT::ForRangesMC_NC(
-        ranges_mc_, ranges_nc_, pkg_idx_,
+        args_.env->ctx, ranges_mc_, ranges_nc_, pkg_idx_,
         [&](const IndexRange& range_mc, const IndexRange& range_nc,
             size_t worker) HWY_ATTR {
           MMZone mm_zone;
@@ -965,9 +971,10 @@ class MMPerPackage {
 
   // Parallel loops over mc/nc blocks of M/range_np, sequential K.
   // Fills `mc x nc` sections of `partial`, then `C`, in parallel.
-  template <typename TA, typename TB, typename TC>
+  template <typename TA, typename TB, typename TC, class MMParallelPolicyT>
-  HWY_INLINE void DoNT_MT_K(const StridedView<TA> A, const bool A_padded,
+  HWY_INLINE void DoNT_MT_K(MMParallelPolicyT, const StridedView<TA> A,
-                            const MatPtrT<TB>& B, RowPtrs<TC> C_rows) const {
+                            const bool A_padded, const MatPtrT<TB>& B,
+                            RowPtrs<TC> C_rows) const {
     static const auto zone = args_.env->ctx.profiler.AddZone("MM.NT_MT_K");
     const size_t kc_max = ranges_kc_.TaskSize();
     HWY_DASSERT(kc_max <= MMStorage::kMaxKC);
@@ -992,8 +999,8 @@ class MMPerPackage {
                        out_tag, args_, C_rows);
       }
     };  // loop_nc
-    args_.env->parallel.ForRangesMC_NC(
+    MMParallelPolicyT::ForRangesMC_NC(
-        ranges_mc_, ranges_nc_, pkg_idx_,
+        args_.env->ctx, ranges_mc_, ranges_nc_, pkg_idx_,
         [&](const IndexRange& range_mc, const IndexRange& range_nc,
             size_t worker) HWY_ATTR {
           MMZone mm_zone;
@@ -1014,6 +1021,7 @@ class MMPerPackage {
   }
 
   // Decompresses all `M x K` from `A` into padded BF16 `A_view`.
+  template <typename MMParallelPolicyT>
   HWY_NOINLINE void DoDecompressA(const MatPtrT<float>& A,
                                   const StridedViewBF A_view,
                                   MMParA par_a) const {
@@ -1064,16 +1072,16 @@ class MMPerPackage {
         // line to avoid false sharing.
         const size_t multiple_K = HWY_MAX(NBF, line_bytes_ / sizeof(BF16));
 
-        args_.env->parallel.ForNP(
+        MMParallelPolicyT::ForNP(args_.env->ctx, all_K, multiple_K, inner_tasks,
-            all_K, multiple_K, inner_tasks, pkg_idx_,
+                                 pkg_idx_,
                                  [&](const IndexRange& range_K, size_t worker) {
                                    do_range(all_M, range_K, worker);
                                  });
         break;
       }
       case MMParA::kM:
-        args_.env->parallel.ForRangeMC(
+        MMParallelPolicyT::ForRangeMC(
-            all_M, pkg_idx_, [&](size_t row_a, size_t worker) {
+            args_.env->ctx, all_M, pkg_idx_, [&](size_t row_a, size_t worker) {
               do_range(IndexRange(row_a, row_a + 1), all_K, worker);
             });
         break;
@@ -1081,12 +1089,13 @@ class MMPerPackage {
   }
 
   // Autotuning wrapper for `DoDecompressA`.
+  template <typename MMParallelPolicyT>
   HWY_INLINE void DecompressA(const MatPtrT<float>& A,
                               const StridedViewBF A_view) const {
     MMAutoTune<MMParA>& autotune = args_.per_key->autotune_par_a[pkg_idx_];
 
     if (HWY_LIKELY(autotune.Best())) {
-      return DoDecompressA(A, A_view, *autotune.Best());
+      return DoDecompressA<MMParallelPolicyT>(A, A_view, *autotune.Best());
     }
 
     // First call: generate candidates.
@@ -1099,7 +1108,7 @@ class MMPerPackage {
 
     const MMParA& par_a = autotune.NextConfig();
     const uint64_t t0 = hwy::timer::Start();
-    DoDecompressA(A, A_view, par_a);
+    DoDecompressA<MMParallelPolicyT>(A, A_view, par_a);
     const uint64_t t1 =
         args_.env->have_timer_stop ? hwy::timer::Stop() : hwy::timer::Start();
     const uint64_t min_elapsed = autotune.NotifyTicks(t1 - t0);
@@ -1185,19 +1194,21 @@ struct MMImpl {
 
     if constexpr (kMaxPackages > 1) {
       // Outermost loop: static NUMA-aware partition of B rows across packages.
-      args.env->parallel.ForPkg(
+      MMNestedParallelPolicy::ForPkg(
-          args.per_key->ranges_np.NumTasks(), [&](size_t pkg_idx) {
+          args.env->ctx, args.per_key->ranges_np.NumTasks(),
+          [&](size_t pkg_idx) {
             MMZone mm_zone;
             mm_zone.MaybeEnter(pkg_idx, zone, args);
             const IndexRange& range_np = args.per_key->ranges_np.Range(pkg_idx);
-            MMPerPackage(A.Extents(), args, config, pkg_idx, range_np)(A, B,
+            MMPerPackage(A.Extents(), args, config, pkg_idx, range_np)(
-                                                                       C_rows);
+                MMNestedParallelPolicy(), A, B, C_rows);
           });
     } else {
       const size_t pkg_idx = 0;
       HWY_DASSERT(args.per_key->ranges_np.NumTasks() == 1);
       const IndexRange& range_np = args.per_key->ranges_np.Range(pkg_idx);
-      MMPerPackage(A.Extents(), args, config, pkg_idx, range_np)(A, B, C_rows);
+      MMPerPackage(A.Extents(), args, config, pkg_idx, range_np)(
+          MMNestedParallelPolicy(), A, B, C_rows);
     }
   }
 };
@@ -1250,8 +1261,7 @@ HWY_NOINLINE MMPerKey* MatMul(const MatPtrT<TA>& A, const MatPtrT<TB>& B,
 
     // invalidates `MMAutoTune::Best()`
     index = env.per_key.size();
-    env.per_key.push_back(
+    env.per_key.push_back(MMPerKey(env.ctx, max_packages, N, sizeof(TC), kNR));
-        MMPerKey(max_packages, N, sizeof(TC), kNR, env.parallel));
   }
   MMPerKey& per_key = env.per_key[index];
   MMAutoTune<MMConfig>& tuner = per_key.autotune;

ops/matmul.cc

@@ -397,34 +397,33 @@ static size_t NPMultiple(const Allocator& allocator, size_t N,
   return np_multiple;
 }
 
-IndexRangePartition MMParallel::RangesOfNP(size_t max_packages, size_t N,
+IndexRangePartition MMRangesOfNP(ThreadingContext& ctx, size_t max_packages,
-                                           size_t sizeof_TC, size_t nr) const {
+                                 size_t N, size_t sizeof_TC, size_t nr) {
-  const size_t num_packages = HWY_MIN(max_packages, ctx_.pools.NumPackages());
+  const size_t num_packages = HWY_MIN(max_packages, ctx.pools.NumPackages());
   return StaticPartition(
       IndexRange(0, N), num_packages,
-      NPMultiple(ctx_.allocator, N, sizeof_TC, nr, num_packages));
+      NPMultiple(ctx.allocator, N, sizeof_TC, nr, num_packages));
 }
 
-MatMulEnv::MatMulEnv(ThreadingContext& ctx)
+MatMulEnv::MatMulEnv(ThreadingContext& ctx) : ctx(ctx), storage(ctx) {
-    : ctx(ctx), parallel(ctx), storage(ctx.allocator, parallel) {
   char cpu100[100];
   have_timer_stop = hwy::platform::HaveTimerStop(cpu100);
 
   row_ptrs.push_back(hwy::AllocateAligned<uint8_t*>(MMStorage::kMaxM));  // C
 }
 
-void BindB(MatPtr& B, size_t sizeof_TC, MMParallel& parallel) {
+void BindB(ThreadingContext& ctx, MatPtr& B, size_t sizeof_TC) {
-  Allocator& allocator = parallel.allocator();
+  Allocator& allocator = ctx.allocator;
   if (!allocator.ShouldBind()) return;
   if (B.Rows() == 1) return;
 
   PROFILER_ZONE("Startup.BindB");
 
   const IndexRangePartition ranges_np =
-      parallel.RangesOfNP(kMaxPackages, B.Rows(), sizeof_TC, kNR);
+      MMRangesOfNP(ctx, kMaxPackages, B.Rows(), sizeof_TC, kNR);
   for (size_t pkg_idx = 0; pkg_idx < ranges_np.NumTasks(); ++pkg_idx) {
     const IndexRange& rows_b = ranges_np.Range(pkg_idx);
-    const size_t node = parallel.Node(pkg_idx);
+    const size_t node = ctx.topology.GetCluster(pkg_idx, 0).Node();
     uintptr_t begin = reinterpret_cast<uintptr_t>(B.RowBytes(rows_b.begin()));
     uintptr_t end = begin + rows_b.Num() * B.Stride() * B.ElementBytes();
     // B row padding is less than the page size, so only bind the subset that
@@ -438,14 +437,14 @@ void BindB(MatPtr& B, size_t sizeof_TC, MMParallel& parallel) {
 }
 
 // C is BF16/float
-void BindC(MatPtr& C, MMParallel& parallel) {
+void BindC(ThreadingContext& ctx, MatPtr& C) {
-  Allocator& allocator = parallel.allocator();
+  Allocator& allocator = ctx.allocator;
   if (!allocator.ShouldBind()) return;
 
   PROFILER_ZONE("Startup.BindC");
 
   const IndexRangePartition ranges_np =
-      parallel.RangesOfNP(kMaxPackages, C.Cols(), C.ElementBytes(), kNR);
+      MMRangesOfNP(ctx, kMaxPackages, C.Cols(), C.ElementBytes(), kNR);
   bool ok = true;
   for (size_t pkg_idx = 0; pkg_idx < ranges_np.NumTasks(); ++pkg_idx) {
     const IndexRange& cols_c = ranges_np.Range(pkg_idx);
@@ -455,7 +454,7 @@ void BindC(MatPtr& C, MMParallel& parallel) {
     const size_t end = hwy::RoundDownTo(cols_c.end() * C.ElementBytes(),
                                         allocator.BasePageBytes());
 
-    const size_t node = parallel.Node(pkg_idx);
+    const size_t node = ctx.topology.GetCluster(pkg_idx, 0).Node();
     for (size_t im = 0; im < C.Rows(); ++im) {
       ok &= allocator.BindMemory(C.RowBytes(im) + begin, end - begin, node);
     }

ops/matmul.h

@@ -53,35 +53,31 @@ constexpr size_t kNR = 4;
 // or less on ISAs with fewer registers, or for the last few rows of A.
 static constexpr size_t kMaxMR = 4;
 
-// Mostly stateless, can be constructed on the fly by weights.cc. Captures the
+IndexRangePartition MMRangesOfNP(ThreadingContext& ctx, size_t max_packages,
-// the ThreadingContext to shorten call sites.
+                                 size_t N, size_t sizeof_TC, size_t nr);
-class MMParallel {
- public:
-  // `ctx` must outlive this object.
-  MMParallel(ThreadingContext& ctx) : ctx_(ctx) {
-    if (ctx_.pools.NumPackages() > kMaxPackages) {
-      HWY_WARN("CPU and --max_packages allow %zu > matmul.h kMaxPackages %zu.",
-               ctx_.pools.NumPackages(), kMaxPackages);
-    }
-  }
 
-  Allocator& allocator() const { return ctx_.allocator; }
+enum class ParallelismType : uint8_t {
+  kNone,
+  // No parallelism.
+  kSequential,
+  // Parallelism at cluster level.
+  kCluster,
+  // Parallelism at package level.
+  kNested,
+};
 
-  // Initial static partitioning of B rows across packages.
+struct MMOptions {
-  IndexRangePartition RangesOfNP(size_t max_packages, size_t N,
+  ParallelismType parallelism_type_ = ParallelismType::kNested;
-                                 size_t sizeof_TC, size_t nr) const;
+  uint8_t cluster_idx_ = 0;
+};
 
-  // For `BindB` and `BindC`.
+struct MMNestedParallelPolicy {
-  size_t Node(size_t pkg_idx) const {
-    return ctx_.topology.GetCluster(pkg_idx, 0).Node();
-  }
-
-  // Calls `func(pkg_idx)` for each package in parallel.
   template <class Func>
-  void ForPkg(const size_t max_packages, const Func& func) {
+  static void ForPkg(ThreadingContext& ctx, const size_t max_packages,
+                     const Func& func) {
     if constexpr (kMaxPackages > 1) {
-      ctx_.pools.AllPackages().Run(
+      ctx.pools.AllPackages().Run(
-          0, HWY_MIN(max_packages, ctx_.pools.NumPackages()),
+          0, HWY_MIN(max_packages, ctx.pools.NumPackages()),
           [&](uint64_t task, size_t pkg_idx) {
             HWY_DASSERT(task == pkg_idx);
             (void)task;
@@ -95,16 +91,17 @@ class MMParallel {
   // Cluster/CCX-aware parallel-for over B rows in `range_np`. `nx_multiple` is
   // the granularity of per-cluster tasks. Calls `func(worker_range, worker)`.
   template <class Func>
-  void ForNP(const IndexRange& range_np, size_t nx_multiple, size_t inner_tasks,
+  static void ForNP(ThreadingContext& ctx, const IndexRange& range_np,
-             size_t pkg_idx, const Func& func) {
+                    size_t nx_multiple, size_t inner_tasks, size_t pkg_idx,
+                    const Func& func) {
     HWY_DASSERT(1 <= inner_tasks && inner_tasks <= 4);
-    const size_t pkg_base = pkg_idx * ctx_.pools.MaxWorkersPerPackage();
+    const size_t pkg_base = pkg_idx * ctx.pools.MaxWorkersPerPackage();
 
     // Single cluster: parallel-for over static partition of `range_np`.
-    hwy::ThreadPool& all_clusters = ctx_.pools.AllClusters(pkg_idx);
+    hwy::ThreadPool& all_clusters = ctx.pools.AllClusters(pkg_idx);
     const size_t num_clusters = all_clusters.NumWorkers();
     if (num_clusters == 1) {
-      hwy::ThreadPool& cluster = ctx_.pools.Cluster(pkg_idx, 0);
+      hwy::ThreadPool& cluster = ctx.pools.Cluster(pkg_idx, 0);
       const IndexRangePartition worker_ranges = StaticPartition(
           range_np, cluster.NumWorkers() * inner_tasks, nx_multiple);
       return ParallelizeOneRange(
@@ -120,9 +117,9 @@ class MMParallel {
     ParallelizeOneRange(
         nx_ranges, all_clusters,
         [&](const IndexRange& nx_range, const size_t cluster_idx) {
-          hwy::ThreadPool& cluster = ctx_.pools.Cluster(pkg_idx, cluster_idx);
+          hwy::ThreadPool& cluster = ctx.pools.Cluster(pkg_idx, cluster_idx);
           const size_t cluster_base =
-              pkg_base + cluster_idx * ctx_.pools.MaxWorkersPerCluster();
+              pkg_base + cluster_idx * ctx.pools.MaxWorkersPerCluster();
           // Parallel-for over sub-ranges of `cluster_range` within the cluster.
           const IndexRangePartition worker_ranges = StaticPartition(
               nx_range, cluster.NumWorkers() * inner_tasks, nx_multiple);
@@ -137,18 +134,19 @@ class MMParallel {
   // Cluster/CCX-aware parallel-for over blocks (separate subranges of A and B
   // rows). Calls `func(range_mc, range_nc, worker)`.
   template <class Func>
-  void ForRangesMC_NC(const IndexRangePartition& ranges_mc,
+  static void ForRangesMC_NC(ThreadingContext& ctx,
-                      const IndexRangePartition& ranges_nc, size_t pkg_idx,
+                             const IndexRangePartition& ranges_mc,
-                      const Func& func) {
+                             const IndexRangePartition& ranges_nc,
-    const size_t pkg_base = pkg_idx * ctx_.pools.MaxWorkersPerPackage();
+                             size_t pkg_idx, const Func& func) {
-    hwy::ThreadPool& all_clusters = ctx_.pools.AllClusters(pkg_idx);
+    const size_t pkg_base = pkg_idx * ctx.pools.MaxWorkersPerPackage();
+    hwy::ThreadPool& all_clusters = ctx.pools.AllClusters(pkg_idx);
     // `all_clusters` is a pool with one worker per cluster in a package.
     const size_t num_clusters = all_clusters.NumWorkers();
     // Single (big) cluster: collapse two range indices into one parallel-for
     // to reduce the number of fork-joins.
     if (num_clusters == 1) {
       const size_t cluster_idx = 0;
-      hwy::ThreadPool& cluster = ctx_.pools.Cluster(pkg_idx, cluster_idx);
+      hwy::ThreadPool& cluster = ctx.pools.Cluster(pkg_idx, cluster_idx);
       // Low-batch: avoid Divide/Remainder.
       if (HWY_UNLIKELY(ranges_mc.NumTasks() == 1)) {
         return ParallelizeOneRange(
@@ -171,8 +169,8 @@ class MMParallel {
         ranges_nc, all_clusters,
         [&](const IndexRange range_nc, size_t cluster_idx) {
           const size_t cluster_base =
-              pkg_base + cluster_idx * ctx_.pools.MaxWorkersPerCluster();
+              pkg_base + cluster_idx * ctx.pools.MaxWorkersPerCluster();
-          hwy::ThreadPool& cluster = ctx_.pools.Cluster(pkg_idx, cluster_idx);
+          hwy::ThreadPool& cluster = ctx.pools.Cluster(pkg_idx, cluster_idx);
           ParallelizeOneRange(ranges_mc, cluster,
                               [&](const IndexRange& range_mc, size_t thread) {
                                 func(range_mc, range_nc, cluster_base + thread);
@@ -182,21 +180,18 @@ class MMParallel {
 
   // Calls `func(row_a, worker)` in parallel.
   template <class Func>
-  void ForRangeMC(const IndexRange& range_mc, size_t pkg_idx,
+  static void ForRangeMC(ThreadingContext& ctx, const IndexRange& range_mc,
-                  const Func& func) {
+                         size_t pkg_idx, const Func& func) {
-    const size_t pkg_base = pkg_idx * ctx_.pools.MaxWorkersPerPackage();
+    const size_t pkg_base = pkg_idx * ctx.pools.MaxWorkersPerPackage();
-    ctx_.pools.Pool(pkg_idx).Run(
+    ctx.pools.Pool(pkg_idx).Run(
         range_mc.begin(), range_mc.end(),
         [&](uint64_t row_a, size_t thread) { func(row_a, pkg_base + thread); });
   }
-
- private:
-  ThreadingContext& ctx_;
 };
 
-void BindB(MatPtr& B, size_t sizeof_TC, MMParallel& parallel);
+void BindB(ThreadingContext& ctx, MatPtr& B, size_t sizeof_TC);
 // C is BF16/float.
-void BindC(MatPtr& C, MMParallel& parallel);
+void BindC(ThreadingContext& ctx, MatPtr& C);
 
 // Lightweight view into `MatStorageT`, with a fixed pitch/stride between rows.
 #pragma pack(push, 1)  // power of two size
@@ -250,15 +245,18 @@ class MMStorage {
 
   // Internally threaded; must not be called concurrently with the same
   // `ThreadingContext` (used via `parallel`).
-  MMStorage(const Allocator& allocator, MMParallel& parallel) {
+  MMStorage(ThreadingContext& ctx) {
     // Per-package allocation so each can decompress A into its own copy.
     // Must be padded, see `DoDecompressA`.
-    parallel.ForPkg(kMaxPackages, [&](size_t pkg_idx) {
+    // Default to nested parallel policy.
+    MMNestedParallelPolicy::ForPkg(ctx, kMaxPackages, [&](size_t pkg_idx) {
+      Allocator& allocator = ctx.allocator;
+
       pkg_A_[pkg_idx].reset(new MatStorageT<BF16>(
           "pkg_A", Extents2D(kMaxM, kMaxK), allocator, MatPadding::kOdd));
 
       if (allocator.ShouldBind()) {
-        const size_t node = parallel.Node(pkg_idx);
+        const size_t node = ctx.topology.GetCluster(pkg_idx, 0).Node();
         size_t bytes = pkg_A_[pkg_idx]->Rows() * pkg_A_[pkg_idx]->Stride() *
                        pkg_A_[pkg_idx]->ElementBytes();
         bytes = hwy::RoundDownTo(bytes, allocator.BasePageBytes());
@@ -607,9 +605,9 @@ class MMKeys {
 
 // Per-MatMul-shape state.
 struct MMPerKey {
-  MMPerKey(size_t max_packages, size_t N, size_t sizeof_TC, size_t nr,
+  MMPerKey(ThreadingContext& ctx, size_t max_packages, size_t N,
-           MMParallel& parallel)
+           size_t sizeof_TC, size_t nr)
-      : ranges_np(parallel.RangesOfNP(max_packages, N, sizeof_TC, nr)) {
+      : ranges_np(MMRangesOfNP(ctx, max_packages, N, sizeof_TC, nr)) {
     HWY_DASSERT(ranges_np.NumTasks() <= max_packages);
   }
 
@@ -639,7 +637,6 @@ struct MatMulEnv {
   // Whether to print the best config immediately after autotuning finished.
   bool print_best = false;
 
-  MMParallel parallel;
   MMStorage storage;
   MMKeys keys;
   std::vector<MMPerKey> per_key;