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project_6/muh/include/muh/tuning/tuning_scan_by_key.cuh
muh-bot a898faa34e [muh] delay v2: reduce_by_key + scan_by_key 全部改为 no_delay 
基于 CCCL delay 系统源码分析 (single_pass_scan_operators.cuh):
  if (gridDim.x < 500) __threadfence_block();  // 小 grid
  else __nanosleep(Delay);                      // 大 grid

BI-V100: 16 SMs × ~2 CTAs/SM = max 32 CTAs → gridDim.x < 500 永远成立
→ 所有 exponential_backoff/backon 在 BI-V100 上退化为 __threadfence_block
→ no_delay 是唯一正确的策略

变更:
- tuning_reduce_by_key.cuh: 280→171 行, 删除 sd() 缩放函数,
  66 条 entry 全部改为 no_delay, 保留 l2_write_latency
- tuning_scan_by_key.cuh: 256→145 行, 同上
- CCCL benchmark-tuned 的 threads/items/load_algorithm 不变
2026-08-04 07:17:34 +00:00

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// muh/include/muh/tuning/tuning_scan_by_key.cuh — BI-V100
//
// Full port from CCCL (2008 lines). SM100: 16, SM90: ~30, SM80: ~30 entries.
// DELAY v2: all no_delay (16 SMs → gridDim.x < 500 → CCCL skips __nanosleep)
// L2WriteLatency preserved from CCCL (one-time constructor wait for L2 visibility)
#pragma once
#include "muh/hardware.cuh"
#include "muh/tuning/common.cuh"
namespace muh::tuning::scan_by_key {
struct ScanByKeyLookbackPolicy {
int threads_per_block; int items_per_thread;
BlockLoadAlgorithm load_algorithm; CacheLoadModifier load_modifier;
BlockStoreAlgorithm store_algorithm; BlockScanAlgorithm scan_algorithm;
LookbackDelayPolicy delay;
};
enum class ScanByKeyAlgorithm { lookback };
struct ScanByKeyPolicy { ScanByKeyAlgorithm algorithm; ScanByKeyLookbackPolicy lookback; };
struct policy_selector {
int key_size; int value_size;
bool value_is_primitive; bool accum_is_primitive;
constexpr bool smem_ok(int tpb, int ipt, bool wt) const {
int pair = key_size + value_size;
int tile = tpb * ipt * pair;
if (wt) tile *= 2;
return tile + 1024 <= 49152;
}
constexpr ScanByKeyLookbackPolicy safe(int tpb, int ipt, BlockLoadAlgorithm la,
CacheLoadModifier lm, BlockStoreAlgorithm sa, LookbackDelayPolicy d) const {
bool wt = (la == BLOCK_LOAD_WARP_TRANSPOSE);
while (!smem_ok(tpb, ipt, wt) && ipt > 1) ipt--;
while (!smem_ok(tpb, ipt, wt) && tpb > 32) tpb -= 32;
return {tpb, ipt, la, lm, sa, BLOCK_SCAN_WARP_SCANS, d};
}
constexpr ScanByKeyLookbackPolicy wt(int tpb, int ipt, CacheLoadModifier lm, int l2w) const {
return safe(tpb, ipt, BLOCK_LOAD_WARP_TRANSPOSE, lm, BLOCK_STORE_WARP_TRANSPOSE,
{LookbackDelayAlgorithm::no_delay, 0, l2w});
}
constexpr ScanByKeyLookbackPolicy dr(int tpb, int ipt, CacheLoadModifier lm, int l2w) const {
return safe(tpb, ipt, BLOCK_LOAD_DIRECT, lm, BLOCK_STORE_DIRECT,
{LookbackDelayAlgorithm::no_delay, 0, l2w});
}
constexpr ScanByKeyLookbackPolicy get_lookback_policy() const {
bool pv = value_is_primitive;
// SM100 tile configs, all no_delay
if (pv) {
if (key_size==1 && value_size==1) return wt(288,13,LOAD_DEFAULT,745);
if (key_size==1 && value_size==2) return wt(288,13,LOAD_DEFAULT,570);
if (key_size==1 && value_size==4) return wt(224,19,LOAD_CA,910);
if (key_size==1 && value_size==8) return wt(192,18,LOAD_CA,1035);
if (key_size==2 && value_size==1) return wt(384,12,LOAD_DEFAULT,840);
if (key_size==2 && value_size==2) return wt(160,14,LOAD_DEFAULT,170);
if (key_size==2 && value_size==4) return wt(160,14,LOAD_DEFAULT,805);
if (key_size==2 && value_size==8) return wt(224,13,LOAD_CA,735);
if (key_size==4 && value_size==1) return wt(224,20,LOAD_CA,155);
if (key_size==4 && value_size==2) return wt(288,13,LOAD_CA,925);
if (key_size==4 && value_size==4) return wt(224,20,LOAD_CA,280); // VLLM HOT PATH
if (key_size==4 && value_size==8) return wt(224,14,LOAD_CA,860);
if (key_size==8 && value_size==1) return wt(160,12,LOAD_DEFAULT,850);
if (key_size==8 && value_size==2) return wt(288,15,LOAD_DEFAULT,335);
if (key_size==8 && value_size==4) return wt(160,22,LOAD_CA,505);
if (key_size==8 && value_size==8) return wt(256,23,LOAD_DEFAULT,810);
}
// SM90
if (pv) {
if (key_size==1 && value_size==1) return dr(128,12,LOAD_DEFAULT,650);
if (key_size==1 && value_size==2) return wt(256,16,LOAD_DEFAULT,995);
if (key_size==1 && value_size==4) return wt(128,15,LOAD_DEFAULT,545);
if (key_size==1 && value_size==8) return wt(224,10,LOAD_DEFAULT,1070);
if (key_size==2 && value_size==1) return dr(128,12,LOAD_DEFAULT,785);
if (key_size==2 && value_size==2) return wt(128,20,LOAD_DEFAULT,445);
if (key_size==2 && value_size==4) return wt(128,22,LOAD_DEFAULT,865);
if (key_size==2 && value_size==8) return wt(224,10,LOAD_DEFAULT,1170);
if (key_size==4 && value_size==1) return dr(128,12,LOAD_DEFAULT,850);
if (key_size==4 && value_size==2) return wt(256,14,LOAD_DEFAULT,965);
if (key_size==4 && value_size==4) return wt(288,14,LOAD_DEFAULT,1005);
if (key_size==4 && value_size==8) return wt(224,14,LOAD_DEFAULT,1195);
if (key_size==8 && value_size==1) return dr(128,12,LOAD_DEFAULT,1010);
if (key_size==8 && value_size==2) return wt(224,10,LOAD_DEFAULT,970);
if (key_size==8 && value_size==4) return wt(192,10,LOAD_DEFAULT,1125);
if (key_size==8 && value_size==8) return wt(224,11,LOAD_DEFAULT,930);
}
if (key_size==16 && accum_is_primitive) {
if (value_size==1) return wt(192,7,LOAD_DEFAULT,975);
if (value_size==2) return wt(224,10,LOAD_DEFAULT,1075);
if (value_size==4) return wt(256,9,LOAD_DEFAULT,1120);
if (value_size==8) return wt(192,9,LOAD_DEFAULT,1200);
}
if (value_size==16) {
if (key_size==1) return wt(128,23,LOAD_DEFAULT,1105);
if (key_size==2) return wt(128,23,LOAD_DEFAULT,1190);
if (key_size==4) return wt(128,23,LOAD_DEFAULT,1030);
if (key_size==8) return wt(192,15,LOAD_DEFAULT,1085);
if (key_size==16) return wt(128,23,LOAD_DEFAULT,1050);
}
// SM80
if (pv) {
if (key_size==1 && value_size==1) return dr(128,12,LOAD_DEFAULT,795);
if (key_size==1 && value_size==2) return wt(288,12,LOAD_DEFAULT,825);
if (key_size==1 && value_size==4) return wt(256,15,LOAD_DEFAULT,640);
if (key_size==1 && value_size==8) return wt(192,10,LOAD_DEFAULT,1040);
if (key_size==2 && value_size==1) return dr(256,8,LOAD_DEFAULT,1070);
if (key_size==2 && value_size==2) return wt(320,14,LOAD_DEFAULT,625);
if (key_size==2 && value_size==4) return wt(256,15,LOAD_DEFAULT,1055);
if (key_size==2 && value_size==8) return wt(160,17,LOAD_DEFAULT,695);
if (key_size==4 && value_size==1) return dr(128,12,LOAD_DEFAULT,1130);
if (key_size==4 && value_size==2) return wt(256,12,LOAD_DEFAULT,1130);
if (key_size==4 && value_size==4) return wt(256,15,LOAD_DEFAULT,1140);
if (key_size==4 && value_size==8) return wt(256,9,LOAD_DEFAULT,635);
if (key_size==8 && value_size==1) return wt(128,11,LOAD_DEFAULT,1120);
if (key_size==8 && value_size==2) return wt(256,10,LOAD_DEFAULT,1115);
if (key_size==8 && value_size==4) return wt(224,13,LOAD_DEFAULT,1060);
if (key_size==8 && value_size==8) return wt(224,10,LOAD_DEFAULT,1160);
}
if (key_size==16 && accum_is_primitive) {
if (value_size==1) return wt(192,7,LOAD_DEFAULT,1120);
if (value_size==2) return wt(192,7,LOAD_DEFAULT,780);
if (value_size==4) return wt(256,7,LOAD_DEFAULT,1170);
if (value_size==8) return wt(128,15,LOAD_DEFAULT,1030);
}
if (value_size==16) {
if (key_size==1) return wt(128,19,LOAD_DEFAULT,1095);
if (key_size==2) return wt(160,14,LOAD_DEFAULT,1105);
if (key_size==4) return wt(128,17,LOAD_DEFAULT,1100);
if (key_size==8) return wt(320,8,LOAD_DEFAULT,220);
if (key_size==16) return wt(128,15,LOAD_DEFAULT,1160);
}
// Default
int mx = key_size > value_size ? key_size : value_size;
int ipt = (mx <= 8) ? 9 : (9*8/(key_size+value_size));
if (ipt<1) ipt=1; if (ipt>9) ipt=9;
return wt(256, ipt, LOAD_DEFAULT, 450);
}
constexpr ScanByKeyPolicy operator()(const hardware_capability& hw) const {
return {ScanByKeyAlgorithm::lookback, get_lookback_policy()};
}
};
} // namespace muh::tuning::scan_by_key
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