[Bug libc/27437] [aarch64]memcpy_simd has performance regression with larger size on Neoverse N1

["xuchunmei at linux dot alibaba.com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=27437

--- Comment #4 from xuchunmei <xuchunmei at linux dot alibaba.com> ---
(In reply to Wilco from comment #3)
> So bench-memcpy-random shows __memcpy_simd is fastest by a good margin for
> small cases. Do you see similar differences between __memcpy_generic and
> __memcpy_simd in bench-memcpy-walk or bench-memcpy-large?

# ./bench-memcpy-walk 
{
 "timing_type": "hp_timing",
 "functions": {
  "memcpy": {
   "bench-variant": "walk",
   "ifuncs": ["__memcpy_thunderx", "__memcpy_thunderx2", "__memcpy_falkor",
"__memcpy_simd", "__memcpy_generic"],
   "results": [
    {
     "length": 128,
     "timings": [33.76, 34.9569, 9.54915, 9.57585, 9.47256]
    },
    {
     "length": 129,
     "timings": [35.2716, 31.849, 30.5517, 29.9549, 31.5533]
    },
    {
     "length": 256,
     "timings": [62.829, 60.8114, 57.7517, 56.2223, 57.1628]
    },
    {
     "length": 257,
     "timings": [49.6077, 47.399, 47.2415, 46.5737, 47.5711]
    },
    {
     "length": 512,
     "timings": [113.586, 113.427, 115.86, 116.922, 116.778]
    },
    {
     "length": 513,
     "timings": [106.793, 101.588, 94.7251, 88.1578, 88.2201]
    },
    {
     "length": 1024,
     "timings": [121.122, 122.055, 128.414, 122.723, 123.736]
    },
    {
     "length": 1025,
     "timings": [210.901, 195.7, 195.425, 181.864, 172.566]
    },
    {
     "length": 2048,
     "timings": [218.448, 224.068, 223.655, 230.854, 216.989]
    },
    {
     "length": 2049,
     "timings": [321.531, 329.909, 289.185, 285.851, 281.323]
    },
    {
     "length": 4096,
     "timings": [374.179, 401.979, 384.495, 392.112, 381.073]
    },
    {
     "length": 4097,
     "timings": [450.306, 510.441, 414.745, 401.545, 401.715]
    },
    {
     "length": 8192,
     "timings": [667.217, 673.253, 677.579, 694.132, 674.405]
    },
    {
     "length": 8193,
     "timings": [679.844, 768.811, 610.683, 591.152, 591.464]
    },
    {
     "length": 16384,
     "timings": [1236.02, 1206.93, 1261.11, 1287.68, 1255.33]
    },
    {
     "length": 16385,
     "timings": [1102.34, 1254.92, 1071.11, 1054.39, 1053.36]
    },
    {
     "length": 32768,
     "timings": [2275.35, 2294.88, 2424.76, 2472.89, 2404.96]
    },
    {
     "length": 32769,
     "timings": [2328.63, 2305.86, 2109.21, 2002.92, 2024.76]
    },
    {
     "length": 65536,
     "timings": [4437.26, 4435.93, 4803.28, 4880.86, 4743.9]
    },
    {
     "length": 65537,
     "timings": [4355.46, 4326.86, 4179.13, 4072.96, 4076.16]
    },
    {
     "length": 131072,
     "timings": [8670.91, 8735.29, 9394.05, 9515.15, 9383.43]
    },
    {
     "length": 131073,
     "timings": [8454.82, 9398.74, 8723.57, 8726.39, 8669.98]
    },
    {
     "length": 262144,
     "timings": [17410.9, 17450.9, 18792.5, 18928.1, 18682.2]
    },
    {
     "length": 262145,
     "timings": [16825.3, 16689.3, 17449.6, 17574.3, 17360.3]
    },
    {
     "length": 524288,
     "timings": [34310.5, 34433.7, 37218.7, 37446.8, 37060.6]
    },
    {
     "length": 524289,
     "timings": [33399.9, 33441.8, 34781.2, 34548.7, 34354.3]
    },
    {
     "length": 1048576,
     "timings": [68204.8, 68134.8, 74178.7, 74529.9, 73581.2]
    },
    {
     "length": 1048577,
     "timings": [64777.2, 65532.3, 69548.6, 69252.3, 68627.3]
    },
    {
     "length": 2097152,
     "timings": [134797, 135150, 146707, 147932, 146395]
    },
    {
     "length": 2097153,
     "timings": [131402, 130510, 141845, 142190, 141580]
    },
    {
     "length": 4194304,
     "timings": [268444, 269134, 292860, 295185, 293134]
    },
    {
     "length": 4194305,
     "timings": [265649, 265709, 287879, 289754, 288134]
    },
    {
     "length": 8388608,
     "timings": [534478, 538868, 585879, 589639, 584779]
    },
    {
     "length": 8388609,
     "timings": [533418, 535318, 581869, 587639, 580609]
    },
    {
     "length": 16777216,
     "timings": [1.07644e+06, 1.07876e+06, 1.17434e+06, 1.18022e+06,
1.17142e+06]
    },
    {
     "length": 16777217,
     "timings": [1.07702e+06, 1.07438e+06, 1.1722e+06, 1.18212e+06,
1.17316e+06]
    },
    {
     "length": 33554432,
     "timings": [2.14187e+06, 2.15503e+06, 2.35112e+06, 2.38628e+06,
2.34704e+06]
    },
    {
     "length": 33554433,
     "timings": [2.16367e+06, 2.15555e+06, 2.35476e+06, 2.36968e+06,
2.35604e+06]
    }]
  }
 }
}

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