Paged KV Types

namespace trt_edgellm

Argument bundles for the CuTe DSL FMHA launchers.

Each public run* entry point fills one of these once from its own arguments and members, and the launcher then spreads it across the generated descriptors. One struct per wrapper shape rather than a single superset: a superset would let a field that matters on one path (kvCacheCapacity on the dense path, tokensPerPage on the paged one) sit silently at zero on another.

These carry no generated types, so this header is safe to include from translation units that use the required FMHA-v2 runner, the optional CUTE_DSL_FMHA_BLACKWELL_ENABLED runner, or both. The descriptor-filling machinery itself lives in cuteDslTensorDescriptors.h, which stays free of any FMHA concept.

Helpers for populating the tensor descriptors emitted by the CuTe DSL C exporter.

Every AOT variant exports its own nominally distinct but layout-identical descriptor structs (fmha_d64_Tensor_q_tensor_t vs fmha_d128_Tensor_q_tensor_t) plus a cute_dsl_<variant>_wrapper entry point. There is no umbrella C type, so descriptor types are recovered here from the signature of the wrapper that consumes them: a call site names only the wrapper and the kernel module, and pairing a descriptor with the wrong variant is not expressible.

The exporter (cutlass/cute/export/c_header_generator.py) always names the members data, dynamic_shapes and dynamic_strides, but emits each array only when its dynamic mask is non-empty. A rank-1 descriptor therefore has no dynamic_strides member at all and needs makeCuSeqLenTensor() rather than the strided builders below.

namespace rt

Functions

inline int32_t pagesPerSlot(int32_t maxCapPadded)

Number of pages a single slot’s padded token capacity spans.

inline int32_t computeMaxPagesPerSeq(int32_t maxKVCacheCapacity)

Maximum number of pages one sequence’s KV capacity spans (the page table’s last dim).

inline int64_t computeMinimumKvPoolPages(

int64_t maxBatchSize,

int64_t maxKVCacheCapacity

)

Computes the paged-KV pool’s minimum active pages: maxBatchSize * ceil(maxKVCacheCapacity / kTOKENS_PER_PAGE). Identity-mapped active slots occupy these first pages. A build may serialize extra retained pages for cross-request reuse, but its engine profile, runtime registry, allocation, and page table must all use that same count. Callers validate positive inputs and validate against kMAX_KV_POOL_PAGES before narrowing to int32.

Variables

int32_t kTOKENS_PER_PAGE = {128}

Page size P for the paged-KV layout (tokens per page).

int32_t kUNUSED_PAGE_ENTRY = {-1}

Sentinel value for an unallocated page-table entry.

int64_t kMAX_KV_POOL_PAGES = {std::numeric_limits<int32_t>::max() / 2}

Largest K-page count for which both the derived V ids and the CuTe FMHA combined K/V page count (2 * numPages) fit a positive int32.

int32_t kMAX_KV_CACHE_CAPACITY = (std::numeric_limits<int32_t>::max() / kTOKENS_PER_PAGE) * kTOKENS_PER_PAGE

Largest token capacity whose page-aligned padded value still fits int32.