为什么我的 Intel Skylake/Kaby Lake CPU 在一个简单的散列表实现中会出现神秘的因子3减速？

简而言之:

我已经实现了一个简单的(多键)哈希表，其桶(包含多个元素)完全适合一个缓存。 插入到一个缓冲桶是非常简单的，而且主循环的关键部分。

我已经实现了三个版本，它们产生相同的结果，并且应该具有相同的行为。

神秘

然而，尽管所有版本都具有完全相同的缓存访问模式并导致相同的哈希表数据，但是我发现性能差异惊人地大了3倍。

与我的 CPU (i7-7700HQ)上的 insert_bad和 insert_alt相比，最好的实现 insert_ok的速度要慢3倍。 一个变体 insert _ bad 是对 insert_ok的一个简单修改，它添加了一个额外的不必要的线性搜索，以便查找要写入的位置(它已经知道了) ，并且不会受到 x3减速的影响。

完全相同的可执行文件显示 insert_ok比其他 CPU (AMD 5950X (Zen 3) ，Intel i7-11800H (Tiger Lake))上的 insert_bad和 insert_alt快1.6倍。

# see https://github.com/cr-marcstevens/hashtable_mystery
$ ./test.sh
model name      : Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
==============================
CXX=g++    CXXFLAGS=-std=c++11 -O2 -march=native -falign-functions=64
tablesize: 117440512 elements: 67108864 loadfactor=0.571429
- test insert_ok : 11200ms
- test insert_bad: 3164ms
(outcome identical to insert_ok: true)
- test insert_alt: 3366ms
(outcome identical to insert_ok: true)


tablesize: 117440813 elements: 67108864 loadfactor=0.571427
- test insert_ok : 10840ms
- test insert_bad: 3301ms
(outcome identical to insert_ok: true)
- test insert_alt: 3579ms
(outcome identical to insert_ok: true)

准则

// insert element in hash_table
inline void insert_ok(uint64_t k)
{
// compute target bucket
uint64_t b = mod(k);
// bounded linear search for first non-full bucket
for (size_t c = 0; c < 1024; ++c)
{
bucket_t& B = table_ok[b];
// if bucket non-full then store element and return
if (B.size != bucket_size)
{
B.keys[B.size] = k;
B.values[B.size] = 1;
++B.size;
++table_count;
return;
}
// increase b w/ wrap around
if (++b == table_size)
b = 0;
}
}
// equivalent to insert_ok
// but uses a stupid linear search to store the element at the target position
inline void insert_bad(uint64_t k)
{
// compute target bucket
uint64_t b = mod(k);
// bounded linear search for first non-full bucket
for (size_t c = 0; c < 1024; ++c)
{
bucket_t& B = table_bad[b];
// if bucket non-full then store element and return
if (B.size != bucket_size)
{
for (size_t i = 0; i < bucket_size; ++i)
{
if (i == B.size)
{
B.keys[i] = k;
B.values[i] = 1;
++B.size;
++table_count;
return;
}
}
}
// increase b w/ wrap around
if (++b == table_size)
b = 0;
}
}
// instead of using bucket_t.size, empty elements are marked by special empty_key value
// a bucket is filled first to last, so bucket is full if last element key != empty_key
uint64_t empty_key = ~uint64_t(0);
inline void insert_alt(uint64_t k)
{
// compute target bucket
uint64_t b = mod(k);
// bounded linear search for first non-full bucket
for (size_t c = 0; c < 1024; ++c)
{
bucket_t& B = table_alt[b];
// if bucket non-full then store element and return
if (B.keys[bucket_size-1] == empty_key)
{
for (size_t i = 0; i < bucket_size; ++i)
{
if (B.keys[i] == empty_key)
{
B.keys[i] = k;
B.values[i] = 1;
++table_count;
return;
}
}
}
// increase b w/ wrap around
if (++b == table_size)
b = 0;
}
}

我的分析

我已经尝试了对循环 C + + 的各种修改，但它本质上是如此简单，编译器将生成相同的程序集。 从产生的装配结果来看，因子3的损失可能会导致什么并不明显。 我试过用透视法测量，但似乎找不到任何有意义的差异。

比较3个版本的组装，它们都只是相对较小的循环，没有任何迹象表明任何接近的东西可能会导致这些版本之间的因子3损失。

因此，我认为3倍的减速是自动预取、分支预测、指令/跳转对齐或这些因素的组合造成的怪异效果。

是否有人有更好的见解或方法来衡量什么影响可能实际上在这里发挥作用？

细节

我已经创建了一个小的可用的 C + + 11示例来演示这个问题。 该代码可以在 < a href = “ https://github.com/cr-marcstevens/hashtable _ secret”rel = “ norefrer”> https://github.com/cr-marcstevens/hashtable_mystery 找到

这也包括我自己的静态二进制文件，它们在我的 CPU 上演示了这个问题，因为不同的编译器可能产生不同的代码。 以及所有三个哈希表版本的转储程序集代码。

性能事件测量

这里有很多性能事件的度量方法，我重点介绍了包括 miss和 stall在内的一些度量方法。 每个项目有两行:

• 第一行对应于 insert_ok，它有减速
• 第二行对应于 insert_alt，它有一个额外的循环和额外的工作，但结束得更快

=== L1-dcache-load-misses ===
insert_ok : 171411476
insert_alt: 244244027
=== L1-dcache-loads ===
insert_ok : 775468123
insert_alt: 1038574743
=== L1-dcache-stores ===
insert_ok : 621353009
insert_alt: 554244145
=== L1-icache-load-misses ===
insert_ok : 69666
insert_alt: 259102
=== LLC-load-misses ===
insert_ok : 70519701
insert_alt: 71399242
=== LLC-loads ===
insert_ok : 130909270
insert_alt: 134776189
=== LLC-store-misses ===
insert_ok : 16782747
insert_alt: 16851787
=== LLC-stores ===
insert_ok : 17072141
insert_alt: 17534866
=== arith.divider_active ===
insert_ok : 26810
insert_alt: 26611
=== baclears.any ===
insert_ok : 2038060
insert_alt: 7648128
=== br_inst_retired.all_branches ===
insert_ok : 546479449
insert_alt: 938434022
=== br_inst_retired.all_branches_pebs ===
insert_ok : 546480454
insert_alt: 938412921
=== br_inst_retired.cond_ntaken ===
insert_ok : 237470651
insert_alt: 433439086
=== br_inst_retired.conditional ===
insert_ok : 477604946
insert_alt: 802468807
=== br_inst_retired.far_branch ===
insert_ok : 1058138
insert_alt: 1052510
=== br_inst_retired.near_call ===
insert_ok : 227076
insert_alt: 227074
=== br_inst_retired.near_return ===
insert_ok : 227072
insert_alt: 227070
=== br_inst_retired.near_taken ===
insert_ok : 307946256
insert_alt: 503926433
=== br_inst_retired.not_taken ===
insert_ok : 237458763
insert_alt: 433429466
=== br_misp_retired.all_branches ===
insert_ok : 36443541
insert_alt: 90626754
=== br_misp_retired.all_branches_pebs ===
insert_ok : 36441027
insert_alt: 90622375
=== br_misp_retired.conditional ===
insert_ok : 36454196
insert_alt: 90591031
=== br_misp_retired.near_call ===
insert_ok : 173
insert_alt: 169
=== br_misp_retired.near_taken ===
insert_ok : 19032467
insert_alt: 40361420
=== branch-instructions ===
insert_ok : 546476228
insert_alt: 938447476
=== branch-load-misses ===
insert_ok : 36441314
insert_alt: 90611299
=== branch-loads ===
insert_ok : 546472151
insert_alt: 938435143
=== branch-misses ===
insert_ok : 36436325
insert_alt: 90597372
=== bus-cycles ===
insert_ok : 222283508
insert_alt: 88243938
=== cache-misses ===
insert_ok : 257067753
insert_alt: 475091979
=== cache-references ===
insert_ok : 445465943
insert_alt: 590770464
=== cpu-clock ===
insert_ok : 10333.94 msec cpu-clock:u # 1.000 CPUs utilized
insert_alt: 4766.53 msec cpu-clock:u # 1.000 CPUs utilized
=== cpu-cycles ===
insert_ok : 25273361574
insert_alt: 11675804743
=== cpu_clk_thread_unhalted.one_thread_active ===
insert_ok : 223196489
insert_alt: 88616919
=== cpu_clk_thread_unhalted.ref_xclk ===
insert_ok : 222719013
insert_alt: 88467292
=== cpu_clk_unhalted.one_thread_active ===
insert_ok : 223380608
insert_alt: 88212476
=== cpu_clk_unhalted.ref_tsc ===
insert_ok : 32663820508
insert_alt: 12901195392
=== cpu_clk_unhalted.ref_xclk ===
insert_ok : 221957996
insert_alt: 88390991
insert_alt: === cpu_clk_unhalted.ring0_trans ===
insert_ok : 374
insert_alt: 373
=== cpu_clk_unhalted.thread ===
insert_ok : 25286801620
insert_alt: 11714137483
=== cycle_activity.cycles_l1d_miss ===
insert_ok : 16278956219
insert_alt: 7417877493
=== cycle_activity.cycles_l2_miss ===
insert_ok : 15607833569
insert_alt: 7054717199
=== cycle_activity.cycles_l3_miss ===
insert_ok : 12987627072
insert_alt: 6745771672
=== cycle_activity.cycles_mem_any ===
insert_ok : 23440206343
insert_alt: 9027220495
=== cycle_activity.stalls_l1d_miss ===
insert_ok : 16194872307
insert_alt: 4718344050
=== cycle_activity.stalls_l2_miss ===
insert_ok : 15350067722
insert_alt: 4578933898
=== cycle_activity.stalls_l3_miss ===
insert_ok : 12697354271
insert_alt: 4457980047
=== cycle_activity.stalls_mem_any ===
insert_ok : 20930005455
insert_alt: 4555461595
=== cycle_activity.stalls_total ===
insert_ok : 22243173394
insert_alt: 6561416461
=== dTLB-load-misses ===
insert_ok : 67817362
insert_alt: 63603879
=== dTLB-loads ===
insert_ok : 775467642
insert_alt: 1038562488
=== dTLB-store-misses ===
insert_ok : 8823481
insert_alt: 13050341
=== dTLB-stores ===
insert_ok : 621353007
insert_alt: 554244145
=== dsb2mite_switches.count ===
insert_ok : 93894397
insert_alt: 315793354
=== dsb2mite_switches.penalty_cycles ===
insert_ok : 9216240937
insert_alt: 206393788
=== dtlb_load_misses.miss_causes_a_walk ===
insert_ok : 177266866
insert_alt: 101439773
=== dtlb_load_misses.stlb_hit ===
insert_ok : 2994329
insert_alt: 35601646
=== dtlb_load_misses.walk_active ===
insert_ok : 4747616986
insert_alt: 3893609232
=== dtlb_load_misses.walk_completed ===
insert_ok : 67817832
insert_alt: 63591832
=== dtlb_load_misses.walk_completed_4k ===
insert_ok : 67817841
insert_alt: 63596148
=== dtlb_load_misses.walk_pending ===
insert_ok : 6495600072
insert_alt: 5987182579
=== dtlb_store_misses.miss_causes_a_walk ===
insert_ok : 89895924
insert_alt: 21841494
=== dtlb_store_misses.stlb_hit ===
insert_ok : 4940907
insert_alt: 21970231
=== dtlb_store_misses.walk_active ===
insert_ok : 1784142210
insert_alt: 903334856
=== dtlb_store_misses.walk_completed ===
insert_ok : 8845884
insert_alt: 13071262
=== dtlb_store_misses.walk_completed_4k ===
insert_ok : 8822993
insert_alt: 12936414
=== dtlb_store_misses.walk_pending ===
insert_ok : 1842905733
insert_alt: 933039119
=== exe_activity.1_ports_util ===
insert_ok : 991400575
insert_alt: 1433908710
=== exe_activity.2_ports_util ===
insert_ok : 782270731
insert_alt: 1314443071
=== exe_activity.3_ports_util ===
insert_ok : 556847358
insert_alt: 1158115803
=== exe_activity.4_ports_util ===
insert_ok : 427323800
insert_alt: 783571280
=== exe_activity.bound_on_stores ===
insert_ok : 299732094
insert_alt: 303475333
=== exe_activity.exe_bound_0_ports ===
insert_ok : 227569792
insert_alt: 348959512
=== frontend_retired.dsb_miss ===
insert_ok : 6771584
insert_alt: 93700643
=== frontend_retired.itlb_miss ===
insert_ok : 1115
insert_alt: 1689
=== frontend_retired.l1i_miss ===
insert_ok : 3639
insert_alt: 3857
=== frontend_retired.l2_miss ===
insert_ok : 2826
insert_alt: 2830
=== frontend_retired.latency_ge_1 ===
insert_ok : 9206268
insert_alt: 178345368
=== frontend_retired.latency_ge_128 ===
insert_ok : 2708
insert_alt: 2703
=== frontend_retired.latency_ge_16 ===
insert_ok : 403492
insert_alt: 820950
=== frontend_retired.latency_ge_2 ===
insert_ok : 4981263
insert_alt: 85781924
=== frontend_retired.latency_ge_256 ===
insert_ok : 802
insert_alt: 970
=== frontend_retired.latency_ge_2_bubbles_ge_1 ===
insert_ok : 56936702
insert_alt: 225712704
=== frontend_retired.latency_ge_2_bubbles_ge_2 ===
insert_ok : 10312026
insert_alt: 163227996
=== frontend_retired.latency_ge_2_bubbles_ge_3 ===
insert_ok : 7599252
insert_alt: 122841752
=== frontend_retired.latency_ge_32 ===
insert_ok : 3599
insert_alt: 3317
=== frontend_retired.latency_ge_4 ===
insert_ok : 2627373
insert_alt: 42287077
=== frontend_retired.latency_ge_512 ===
insert_ok : 418
insert_alt: 241
=== frontend_retired.latency_ge_64 ===
insert_ok : 2474
insert_alt: 2802
=== frontend_retired.latency_ge_8 ===
insert_ok : 528748
insert_alt: 951836
=== frontend_retired.stlb_miss ===
insert_ok : 769
insert_alt: 562
=== hw_interrupts.received ===
insert_ok : 9330
insert_alt: 3738
=== iTLB-load-misses ===
insert_ok : 456094
insert_alt: 90739
=== iTLB-loads ===
insert_ok : 949
insert_alt: 1031
=== icache_16b.ifdata_stall ===
insert_ok : 1145821
insert_alt: 862403
=== icache_64b.iftag_hit ===
insert_ok : 1378406022
insert_alt: 4459469241
=== icache_64b.iftag_miss ===
insert_ok : 61812
insert_alt: 57204
=== icache_64b.iftag_stall ===
insert_ok : 56551468
insert_alt: 82354039
=== idq.all_dsb_cycles_4_uops ===
insert_ok : 896374829
insert_alt: 1610100578
=== idq.all_dsb_cycles_any_uops ===
insert_ok : 1217878089
insert_alt: 2739912727
=== idq.all_mite_cycles_4_uops ===
insert_ok : 315979501
insert_alt: 480165021
=== idq.all_mite_cycles_any_uops ===
insert_ok : 1053703958
insert_alt: 2251382760
=== idq.dsb_cycles ===
insert_ok : 1218891711
insert_alt: 2744099964
=== idq.dsb_uops ===
insert_ok : 5828442701
insert_alt: 10445095004
=== idq.mite_cycles ===
insert_ok : 470409312
insert_alt: 1664892371
=== idq.mite_uops ===
insert_ok : 1407396065
insert_alt: 4515396737
=== idq.ms_cycles ===
insert_ok : 583601361
insert_alt: 587996351
=== idq.ms_dsb_cycles ===
insert_ok : 218346
insert_alt: 74155
=== idq.ms_mite_uops ===
insert_ok : 1266443204
insert_alt: 1277980465
=== idq.ms_switches ===
insert_ok : 149106449
insert_alt: 150392336
=== idq.ms_uops ===
insert_ok : 1266950097
insert_alt: 1277330690
=== idq_uops_not_delivered.core ===
insert_ok : 1871959581
insert_alt: 6531069387
=== idq_uops_not_delivered.cycles_0_uops_deliv.core ===
insert_ok : 289301660
insert_alt: 946930713
=== idq_uops_not_delivered.cycles_fe_was_ok ===
insert_ok : 24668869613
insert_alt: 9335642949
=== idq_uops_not_delivered.cycles_le_1_uop_deliv.core ===
insert_ok : 393750384
insert_alt: 1344106460
=== idq_uops_not_delivered.cycles_le_2_uop_deliv.core ===
insert_ok : 506090534
insert_alt: 1824690188
=== idq_uops_not_delivered.cycles_le_3_uop_deliv.core ===
insert_ok : 688462029
insert_alt: 2416339045
=== ild_stall.lcp ===
insert_ok : 380
insert_alt: 480
=== inst_retired.any ===
insert_ok : 4760842560
insert_alt: 5470438932
=== inst_retired.any_p ===
insert_ok : 4760919037
insert_alt: 5470404264
=== inst_retired.prec_dist ===
insert_ok : 4760801654
insert_alt: 5470649220
=== inst_retired.total_cycles_ps ===
insert_ok : 25175372339
insert_alt: 11718929626
=== instructions ===
insert_ok : 4760805219
insert_alt: 5470497783
=== int_misc.clear_resteer_cycles ===
insert_ok : 199623562
insert_alt: 671083279
=== int_misc.recovery_cycles ===
insert_ok : 314434729
insert_alt: 704406698
=== itlb.itlb_flush ===
insert_ok : 303
insert_alt: 248
=== itlb_misses.miss_causes_a_walk ===
insert_ok : 19537
insert_alt: 116729
=== itlb_misses.stlb_hit ===
insert_ok : 11323
insert_alt: 5557
=== itlb_misses.walk_active ===
insert_ok : 2809766
insert_alt: 4070194
=== itlb_misses.walk_completed ===
insert_ok : 24298
insert_alt: 45251
=== itlb_misses.walk_completed_4k ===
insert_ok : 34084
insert_alt: 29759
=== itlb_misses.walk_pending ===
insert_ok : 853764
insert_alt: 2817933
=== l1d.replacement ===
insert_ok : 171135334
insert_alt: 244967326
=== l1d_pend_miss.fb_full ===
insert_ok : 354631656
insert_alt: 382309583
=== l1d_pend_miss.pending ===
insert_ok : 16792436441
insert_alt: 22979721104
=== l1d_pend_miss.pending_cycles ===
insert_ok : 16377420892
insert_alt: 7349245429
=== l1d_pend_miss.pending_cycles_any ===
insert_ok : insert_alt: === l2_lines_in.all ===
insert_ok : 303009088
insert_alt: 411750486
=== l2_lines_out.non_silent ===
insert_ok : 157208112
insert_alt: 309484666
=== l2_lines_out.silent ===
insert_ok : 127379047
insert_alt: 84169481
=== l2_lines_out.useless_hwpf ===
insert_ok : 70374658
insert_alt: 144359127
=== l2_lines_out.useless_pref ===
insert_ok : 70747103
insert_alt: 142931540
=== l2_rqsts.all_code_rd ===
insert_ok : 71254
insert_alt: 242327
=== l2_rqsts.all_demand_data_rd ===
insert_ok : 137366274
insert_alt: 143507049
=== l2_rqsts.all_demand_miss ===
insert_ok : 150071420
insert_alt: 150820168
=== l2_rqsts.all_demand_references ===
insert_ok : 154854022
insert_alt: 160487082
=== l2_rqsts.all_pf ===
insert_ok : 170261458
insert_alt: 282476184
=== l2_rqsts.all_rfo ===
insert_ok : 17575896
insert_alt: 16938897
=== l2_rqsts.code_rd_hit ===
insert_ok : 79800
insert_alt: 381566
=== l2_rqsts.code_rd_miss ===
insert_ok : 25800
insert_alt: 33755
=== l2_rqsts.demand_data_rd_hit ===
insert_ok : 5191029
insert_alt: 9831101
=== l2_rqsts.demand_data_rd_miss ===
insert_ok : 132253891
insert_alt: 133965310
=== l2_rqsts.miss ===
insert_ok : 305347974
insert_alt: 414758839
=== l2_rqsts.pf_hit ===
insert_ok : 14639778
insert_alt: 19484420
=== l2_rqsts.pf_miss ===
insert_ok : 156092998
insert_alt: 263293430
=== l2_rqsts.references ===
insert_ok : 326549998
insert_alt: 443460029
=== l2_rqsts.rfo_hit ===
insert_ok : 11650
insert_alt: 21474
=== l2_rqsts.rfo_miss ===
insert_ok : 17544467
insert_alt: 16835137
=== l2_trans.l2_wb ===
insert_ok : 157044674
insert_alt: 308107712
=== ld_blocks.no_sr ===
insert_ok : 14
insert_alt: 13
=== ld_blocks.store_forward ===
insert_ok : 158
insert_alt: 128
=== ld_blocks_partial.address_alias ===
insert_ok : 5155853
insert_alt: 17867414
=== load_hit_pre.sw_pf ===
insert_ok : 10840795
insert_alt: 11072297
=== longest_lat_cache.miss ===
insert_ok : 257061118
insert_alt: 471152073
=== longest_lat_cache.reference ===
insert_ok : 445701577
insert_alt: 583870610
=== machine_clears.count ===
insert_ok : 3926377
insert_alt: 4280080
=== machine_clears.memory_ordering ===
insert_ok : 97177
insert_alt: 25407
=== machine_clears.smc ===
insert_ok : 138579
insert_alt: 305423
=== mem-stores ===
insert_ok : 621353009
insert_alt: 554244143
=== mem_inst_retired.all_loads ===
insert_ok : 775473590
insert_alt: 1038559807
=== mem_inst_retired.all_stores ===
insert_ok : 621353013
insert_alt: 554244145
=== mem_inst_retired.lock_loads ===
insert_ok : 85
insert_alt: 85
=== mem_inst_retired.split_loads ===
insert_ok : 171
insert_alt: 174
=== mem_inst_retired.split_stores ===
insert_ok : 53
insert_alt: 49
=== mem_inst_retired.stlb_miss_loads ===
insert_ok : 68308539
insert_alt: 18088047
=== mem_inst_retired.stlb_miss_stores ===
insert_ok : 264054
insert_alt: 819551
=== mem_load_l3_hit_retired.xsnp_none ===
insert_ok : 231116
insert_alt: 175217
=== mem_load_retired.fb_hit ===
insert_ok : 6510722
insert_alt: 95952490
=== mem_load_retired.l1_hit ===
insert_ok : 698271530
insert_alt: 920982402
=== mem_load_retired.l1_miss ===
insert_ok : 69525335
insert_alt: 20089897
=== mem_load_retired.l2_hit ===
insert_ok : 1451905
insert_alt: 773356
=== mem_load_retired.l2_miss ===
insert_ok : 68085186
insert_alt: 19474303
=== mem_load_retired.l3_hit ===
insert_ok : 222829
insert_alt: 155958
=== mem_load_retired.l3_miss ===
insert_ok : 67879593
insert_alt: 19244746
=== memory_disambiguation.history_reset ===
insert_ok : 97621
insert_alt: 25831
=== minor-faults ===
insert_ok : 1048716
insert_alt: 1048718
=== node-loads ===
insert_ok : 71473780
insert_alt: 71377840
=== node-stores ===
insert_ok : 16781161
insert_alt: 16842666
=== offcore_requests.all_data_rd ===
insert_ok : 284186682
insert_alt: 392110677
=== offcore_requests.all_requests ===
insert_ok : 530876505
insert_alt: 777784382
=== offcore_requests.demand_code_rd ===
insert_ok : 34252
insert_alt: 45896
=== offcore_requests.demand_data_rd ===
insert_ok : 133468710
insert_alt: 134288893
=== offcore_requests.demand_rfo ===
insert_ok : 17612516
insert_alt: 17062276
=== offcore_requests.l3_miss_demand_data_rd ===
insert_ok : 71616594
insert_alt: 82917520
=== offcore_requests_buffer.sq_full ===
insert_ok : 2001445
insert_alt: 3113287
=== offcore_requests_outstanding.all_data_rd ===
insert_ok : 35577129549
insert_alt: 78698308135
=== offcore_requests_outstanding.cycles_with_data_rd ===
insert_ok : 17518017620
insert_alt: 7940272202
=== offcore_requests_outstanding.demand_code_rd ===
insert_ok : 11085819
insert_alt: 9390881
=== offcore_requests_outstanding.demand_data_rd ===
insert_ok : 15902243707
insert_alt: 21097348926
=== offcore_requests_outstanding.demand_data_rd_ge_6 ===
insert_ok : 1225437
insert_alt: 317436422
=== offcore_requests_outstanding.demand_rfo ===
insert_ok : 1074492442
insert_alt: 1157902315
=== offcore_response.demand_code_rd.any_response ===
insert_ok : 53675
insert_alt: 69683
=== offcore_response.demand_code_rd.l3_hit.any_snoop ===
insert_ok : 19407
insert_alt: 29704
=== offcore_response.demand_code_rd.l3_hit.snoop_none ===
insert_ok : 12675
insert_alt: 11951
=== offcore_response.demand_code_rd.l3_miss.any_snoop ===
insert_ok : 34617
insert_alt: 40868
=== offcore_response.demand_code_rd.l3_miss.spl_hit ===
insert_ok : 0
insert_alt: 753
=== offcore_response.demand_data_rd.any_response ===
insert_ok : 131014821
insert_alt: 134813171
=== offcore_response.demand_data_rd.l3_hit.any_snoop ===
insert_ok : 59713328
insert_alt: 50254543
=== offcore_response.demand_data_rd.l3_miss.any_snoop ===
insert_ok : 71431585
insert_alt: 83916030
=== offcore_response.demand_data_rd.l3_miss.spl_hit ===
insert_ok : 244837
insert_alt: 6441992
=== offcore_response.demand_rfo.any_response ===
insert_ok : 16876557
insert_alt: 17619450
=== offcore_response.demand_rfo.l3_hit.any_snoop ===
insert_ok : 907432
insert_alt: 45127
=== offcore_response.demand_rfo.l3_hit.snoop_none ===
insert_ok : 787567
insert_alt: 794579
=== offcore_response.demand_rfo.l3_hit_e.any_snoop ===
insert_ok : 496938
insert_alt: 173658
=== offcore_response.demand_rfo.l3_hit_e.snoop_none ===
insert_ok : 779919
insert_alt: 50575
=== offcore_response.demand_rfo.l3_hit_m.any_snoop ===
insert_ok : 128627
insert_alt: 25483
=== offcore_response.demand_rfo.l3_miss.any_snoop ===
insert_ok : 16782186
insert_alt: 16847970
=== offcore_response.demand_rfo.l3_miss.snoop_none ===
insert_ok : 16782647
insert_alt: 16850104
=== offcore_response.demand_rfo.l3_miss.spl_hit ===
insert_ok : 0
insert_alt: 1364
=== offcore_response.other.any_response ===
insert_ok : 137231000
insert_alt: 189526494
=== offcore_response.other.l3_hit.any_snoop ===
insert_ok : 62695084
insert_alt: 51005882
=== offcore_response.other.l3_hit.snoop_none ===
insert_ok : 62975018
insert_alt: 50217349
=== offcore_response.other.l3_hit_e.any_snoop ===
insert_ok : 62770215
insert_alt: 50691817
=== offcore_response.other.l3_hit_e.snoop_none ===
insert_ok : 62602591
insert_alt: 50642954
=== offcore_response.other.l3_miss.any_snoop ===
insert_ok : 74247236
insert_alt: 139212975
=== offcore_response.other.l3_miss.snoop_none ===
insert_ok : 75911794
insert_alt: 141076520
=== other_assists.any ===
insert_ok : 1
insert_alt: 3
=== page-faults ===
insert_ok : 1048719
insert_alt: 1048718
=== partial_rat_stalls.scoreboard ===
insert_ok : 530950991
insert_alt: 539869553
=== ref-cycles ===
insert_ok : 32546980212
insert_alt: 12930921138
=== resource_stalls.any ===
insert_ok : 21923576648
insert_alt: 5205690082
=== resource_stalls.sb ===
insert_ok : 397908667
insert_alt: 402738367
=== rs_events.empty_cycles ===
insert_ok : 1173721723
insert_alt: 1880165720
=== rs_events.empty_end ===
insert_ok : 87752182
insert_alt: 160792701
=== sw_prefetch_access.t0 ===
insert_ok : 20835202
insert_alt: 20599176
=== task-clock ===
insert_ok : 10416.86 msec task-clock:u # 1.000 CPUs utilized
insert_alt: 4767.78 msec task-clock:u # 1.000 CPUs utilized
=== tlb_flush.stlb_any ===
insert_ok : 1835393
insert_alt: 1835396
=== topdown-fetch-bubbles ===
insert_ok : 1904143421
insert_alt: 6543146396
=== topdown-slots-issued ===
insert_ok : 7538371393
insert_alt: 14449966516
=== topdown-slots-retired ===
insert_ok : 5267325162
insert_alt: 5849706597
=== uops_dispatched_port.port_0 ===
insert_ok : 1252121297
insert_alt: 1489605354
=== uops_dispatched_port.port_1 ===
insert_ok : 1379316967
insert_alt: 1585037107
=== uops_dispatched_port.port_2 ===
insert_ok : 1140861153
insert_alt: 1785053149
=== uops_dispatched_port.port_3 ===
insert_ok : 1187151423
insert_alt: 1828975838
=== uops_dispatched_port.port_4 ===
insert_ok : 1577171758
insert_alt: 1557761857
=== uops_dispatched_port.port_5 ===
insert_ok : 1341370655
insert_alt: 1653599117
=== uops_dispatched_port.port_6 ===
insert_ok : 1856735970
insert_alt: 4387464794
=== uops_dispatched_port.port_7 ===
insert_ok : 508351498
insert_alt: 603583315
=== uops_executed.core ===
insert_ok : 7225522677
insert_alt: 12716368190
=== uops_executed.core_cycles_ge_1 ===
insert_ok : 3041586797
insert_alt: 5168421550
=== uops_executed.core_cycles_ge_2 ===
insert_ok : 2017794537
insert_alt: 3653591208
=== uops_executed.core_cycles_ge_3 ===
insert_ok : 1225785335
insert_alt: 2316014066
=== uops_executed.core_cycles_ge_4 ===
insert_ok : 657121809
insert_alt: 1143390519
=== uops_executed.core_cycles_none ===
insert_ok : 22191507320
insert_alt: 6563722081
=== uops_executed.cycles_ge_1_uop_exec ===
insert_ok : 3040999757
insert_alt: 5175668459
=== uops_executed.cycles_ge_2_uops_exec ===
insert_ok : 2015520940
insert_alt: 3659989196
=== uops_executed.cycles_ge_3_uops_exec ===
insert_ok : 1224025952
insert_alt: 2319025110
=== uops_executed.cycles_ge_4_uops_exec ===
insert_ok : 657094113
insert_alt: 1141381027
=== uops_executed.stall_cycles ===
insert_ok : 22350754164
insert_alt: 6590978048
=== uops_executed.thread ===
insert_ok : 7214521925
insert_alt: 12697219901
=== uops_executed.x87 ===
insert_ok : 2992
insert_alt: 3337
=== uops_issued.any ===
insert_ok : 7531354736
insert_alt: 14462113169
=== uops_issued.slow_lea ===
insert_ok : 2136241
insert_alt: 2115308
=== uops_issued.stall_cycles ===
insert_ok : 23244177475
insert_alt: 7416801878
=== uops_retired.macro_fused ===
insert_ok : 410461916
insert_alt: 735050350
=== uops_retired.retire_slots ===
insert_ok : 5265023980
insert_alt: 5855259326
=== uops_retired.stall_cycles ===
insert_ok : 23513958928
insert_alt: 9630258867
=== uops_retired.total_cycles ===
insert_ok : 25266688635
insert_alt: 11703285605

背景资料

我正在用 C + + 11实现一个密码分析攻击，需要找到两个大型列表(都是动态生成的)之间的许多冲突。 因此，攻击的关键部分只包括两个关键循环:

1. 首先用一个列表填充哈希表
2. 然后将其他列表与哈希表进行匹配。

因此，哈希表操作对性能至关重要，因子3的减速意味着攻击的速度减慢了3倍。

关于设计: 除了尽量减少内存使用之外，我还试图让一个典型的哈希表操作仅在一个单独的缓存上进行操作。正如我预期的那样，这将提高整体攻击性能，特别是在运行所有 CPU 核心的攻击时。