实习的公司因为各类原因共享内存用得特别多，为了将数据容器放在共享内存上，也写了很多轮子。刚好看到Boost:interprocess，接口是足够现代了，但是不知道性能如何。所以在这里做了一个benchmark。
boost
google/benchmark
cd $benchmark_dir && mkdir build && cd build && cmake -DCMAKE_BUILD_TYPE=Release && make
Run on (4 X 2700 MHz CPU s)
CPU Caches:
L1 Data 32K (x2)
L1 Instruction 32K (x2)
L2 Unified 262K (x2)
L3 Unified 3145K (x1)
Load Average: 4.02, 3.21, 2.97
--------------------------------------------------------------------------------------------
Benchmark Time CPU Iterations
--------------------------------------------------------------------------------------------
raw_array_sequential_assign_benchmark/8 3 ns 3 ns 217126976
raw_array_sequential_assign_benchmark/64 25 ns 23 ns 31862210
raw_array_sequential_assign_benchmark/512 172 ns 171 ns 4039448
raw_array_sequential_assign_benchmark/1024 338 ns 337 ns 2076603
raw_array_random_assign_benchmark/8 5 ns 4 ns 177247049
raw_array_random_assign_benchmark/64 31 ns 31 ns 22002961
raw_array_random_assign_benchmark/512 270 ns 261 ns 2531069
raw_array_random_assign_benchmark/1024 508 ns 507 ns 1387485
std_vector_sequential_assign_benchmark/8 2 ns 2 ns 432785345
std_vector_sequential_assign_benchmark/64 7 ns 7 ns 104479171
std_vector_sequential_assign_benchmark/512 47 ns 47 ns 14883357
std_vector_sequential_assign_benchmark/1024 85 ns 85 ns 8173369
std_vector_random_assign_benchmark/8 4 ns 4 ns 178199120
std_vector_random_assign_benchmark/64 32 ns 31 ns 22105589
std_vector_random_assign_benchmark/512 259 ns 258 ns 2680852
std_vector_random_assign_benchmark/1024 522 ns 515 ns 1389523
interprocess_vector_sequential_assign_benchmark/8 8 ns 8 ns 84849513
interprocess_vector_sequential_assign_benchmark/64 63 ns 63 ns 10913456
interprocess_vector_sequential_assign_benchmark/512 406 ns 406 ns 1701127
interprocess_vector_sequential_assign_benchmark/1024 802 ns 800 ns 862611
interprocess_vector_random_assign_benchmark/8 9 ns 9 ns 79439836
interprocess_vector_random_assign_benchmark/64 73 ns 73 ns 9600088
interprocess_vector_random_assign_benchmark/512 539 ns 536 ns 1227747
interprocess_vector_random_assign_benchmark/1024 1053 ns 1049 ns 674699
std::vector对比interprocess::vector在随机赋值时快很多，查看汇编码发现compiler对std::vector进行了simd的优化，而对于interprocess::vector，compiler就发现不了顺序这个优化点.
对于raw array，我加了volatile阻止优化，所以速度比std::vector要慢了一些。(如果不对数组加volatile修饰符防止优化,那么整段赋值代码都会因为数组本身在后面没有被用到而优化掉)
Run on (4 X 2700 MHz CPU s)
CPU Caches:
L1 Data 32K (x2)
L1 Instruction 32K (x2)
L2 Unified 262K (x2)
L3 Unified 3145K (x1)
Load Average: 2.70, 2.44, 2.59
---------------------------------------------------------------------------------
Benchmark Time CPU Iterations
---------------------------------------------------------------------------------
std_map_insert_benchmark/8 32 ns 32 ns 19554056
std_map_insert_benchmark/64 382 ns 381 ns 1784494
std_map_insert_benchmark/512 16952 ns 16774 ns 42543
std_map_insert_benchmark/4096 343687 ns 332633 ns 2251
std_map_insert_benchmark/32768 4433556 ns 4423133 ns 143
std_map_insert_benchmark/262144 130912831 ns 129502800 ns 5
std_map_insert_benchmark/2097152 2752607513 ns 2679438000 ns 1
std_map_insert_benchmark/8388608 14061497385 ns 13477410000 ns 1
interprocess_map_insert_benchmark/8 256 ns 254 ns 2750653
interprocess_map_insert_benchmark/64 2855 ns 2846 ns 235724
interprocess_map_insert_benchmark/512 45160 ns 44679 ns 15346
interprocess_map_insert_benchmark/4096 622551 ns 616071 ns 976
interprocess_map_insert_benchmark/32768 12957082 ns 12429405 ns 74
interprocess_map_insert_benchmark/262144 182152925 ns 181168333 ns 3
interprocess_map_insert_benchmark/2097152 4080912673 ns 3795930000 ns 1
interprocess_map_insert_benchmark/8388608 17511696908 ns 16895284000 ns 1
可以发现随着插入数量的增加，速度开始趋同，相比较各类指针偏移操作，本身插入逻辑更耗时间。但是在key个数较小的时候，interprocess::offset_ptr的性能损耗是不容忽视的。
std_map_lookup_benchmark/8 24 ns 23 ns 29428210
std_map_lookup_benchmark/64 499 ns 484 ns 1506329
std_map_lookup_benchmark/512 8235 ns 8208 ns 86711
std_map_lookup_benchmark/4096 182682 ns 181943 ns 3852
std_map_lookup_benchmark/32768 3731340 ns 3689636 ns 184
std_map_lookup_benchmark/262144 88041652 ns 87878429 ns 7
std_map_lookup_benchmark/2097152 1375593998 ns 1370821000 ns 1
std_map_lookup_benchmark/8388608 8146980286 ns 8032067000 ns 1
std_hashmap_lookup_benchmark/8 165 ns 160 ns 4420699
std_hashmap_lookup_benchmark/64 1079 ns 1067 ns 644241
std_hashmap_lookup_benchmark/512 9285 ns 8824 ns 81766
std_hashmap_lookup_benchmark/4096 94218 ns 93241 ns 7391
std_hashmap_lookup_benchmark/32768 1295797 ns 1267359 ns 560
std_hashmap_lookup_benchmark/262144 26021905 ns 25794037 ns 27
std_hashmap_lookup_benchmark/2097152 296494872 ns 290691000 ns 2
std_hashmap_lookup_benchmark/8388608 1378290361 ns 1361531000 ns 1
interprocess_map_lookup_benchmark/8 175 ns 171 ns 4113896
interprocess_map_lookup_benchmark/64 2013 ns 1992 ns 318863
interprocess_map_lookup_benchmark/512 38164 ns 37539 ns 17372
interprocess_map_lookup_benchmark/4096 540232 ns 534830 ns 1295
interprocess_map_lookup_benchmark/32768 9113175 ns 9065047 ns 85
interprocess_map_lookup_benchmark/262144 206415034 ns 200967667 ns 3
interprocess_map_lookup_benchmark/2097152 2863882061 ns 2815927000 ns 1
interprocess_map_lookup_benchmark/8388608 13772586489 ns 13680254000 ns 1
interprocess_hashmap_lookup_benchmark/8 221 ns 198 ns 3189836
interprocess_hashmap_lookup_benchmark/64 1868 ns 1783 ns 413399
interprocess_hashmap_lookup_benchmark/512 30387 ns 16947 ns 40853
interprocess_hashmap_lookup_benchmark/4096 174154 ns 152821 ns 3900
interprocess_hashmap_lookup_benchmark/32768 2893169 ns 2792449 ns 254
interprocess_hashmap_lookup_benchmark/262144 41644076 ns 40875647 ns 17
interprocess_hashmap_lookup_benchmark/2097152 440294224 ns 431269000 ns 2
interprocess_hashmap_lookup_benchmark/8388608 3360580116 ns 2522784000 ns 1
以上是在大小为n的容器上进行100,000次查询的耗时 hashmap在容器大时查询速度对比红黑树实现在键-值对数量大于百万后有明显速度优势，同时基于共享内存的hashmap性能与stl的hashmap差异不大，但是红黑树实现的速度差异非常大，基于共享内存的红黑树耗时增长接近现性