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Posted to github@arrow.apache.org by "klion26 (via GitHub)" <gi...@apache.org> on 2026/05/07 11:19:19 UTC
Re: [PR] [Variant] Align cast logic for from/to_decimal for variant [arrow-rs]
klion26 commented on PR #9689:
URL: https://github.com/apache/arrow-rs/pull/9689#issuecomment-4396637437
@scovich @alamb I run the benchmark on ec2(Graviton, instance/cpu info attached below), and the regression exist, I've also tried the following, did not find any useful information yet
- compare the result of `perf stat -e cycles,instructions,cache-references,cache-misses,branch-misses,cpu-clock,task-clock`(details attached below)
- compare the result of `valgrind --tool=callgrind --branch-sim=yes` (details attached below)
- change `#[inline(always)]` to `#[inline]`
The result of `critcmp` is （left is from main branch, right from current branch)
<img width="1260" height="334" alt="3a9451e4c795a8d8349f85d53b52b5a9" src="https://github.com/user-attachments/assets/f54fbb8c-e5bd-4acd-9d0e-8b3adfea69ac" />
> Instance type: t4g.small
> uname: Linux ip-172-31-35-37.x.y.z.a.amzn2023.aarch64 #1 SMP Fri May 1 14:08:03 UTC 2026 aarch64 aarch64 aarch64 GNU/Linux
<details>
<summary>valgrind compare</summary>
<p>
current branch
```
==48976== Callgrind, a call-graph generating cache profiler
==48976== Copyright (C) 2002-2017, and GNU GPL'd, by Josef Weidendorfer et al.
==48976== Using Valgrind-3.19.0 and LibVEX; rerun with -h for copyright info
==48976== Command: ./variant_cast_cast_kernels-589283a85a93d289 --bench cast\ decimal32\ to\ uint8
==48976==
==48976== For interactive control, run 'callgrind_control -h'.
==48977==
==48977== Events : Ir Bc Bcm Bi Bim
==48977== Collected : 663142 107976 5969 392 109
==48977==
==48977== I refs: 663,142
==48977==
==48977== Branches: 108,368 (107,976 cond + 392 ind)
==48977== Mispredicts: 6,078 ( 5,969 cond + 109 ind)
==48977== Mispred rate: 5.6% ( 5.5% + 27.8% )
"cast decimal32 to uint8"
time: [7.3337 ms 7.3430 ms 7.3539 ms]
change: [+7692.6% +7730.7% +7769.2%] (p = 0.00 < 0.05)
Performance has regressed.
Found 4 outliers among 100 measurements (4.00%)
1 (1.00%) high mild
3 (3.00%) high severe
==48976==
==48976== Events : Ir Bc Bcm Bi Bim
==48976== Collected : 4275596549 515310914 27010015 3919351 14426
==48976==
==48976== I refs: 4,275,596,549
==48976==
==48976== Branches: 519,230,265 (515,310,914 cond + 3,919,351 ind)
==48976== Mispredicts: 27,024,441 ( 27,010,015 cond + 14,426 ind)
==48976== Mispred rate: 5.2% ( 5.2% + 0.4% )
```
main-branch
```
==48981== Callgrind, a call-graph generating cache profiler
==48981== Copyright (C) 2002-2017, and GNU GPL'd, by Josef Weidendorfer et al.
==48981== Using Valgrind-3.19.0 and LibVEX; rerun with -h for copyright info
==48981== Command: ./main_cast_kernels-589283a85a93d289 --bench cast\ decimal32\ to\ uint8
==48981==
==48981== For interactive control, run 'callgrind_control -h'.
==48982==
==48982== Events : Ir Bc Bcm Bi Bim
==48982== Collected : 663159 107990 5961 392 109
==48982==
==48982== I refs: 663,159
==48982==
==48982== Branches: 108,382 (107,990 cond + 392 ind)
==48982== Mispredicts: 6,070 ( 5,961 cond + 109 ind)
==48982== Mispred rate: 5.6% ( 5.5% + 27.8% )
"cast decimal32 to uint8"
time: [7.2994 ms 7.3039 ms 7.3086 ms]
change: [−0.6951% −0.5323% −0.3939%] (p = 0.00 < 0.05)
Change within noise threshold.
Found 2 outliers among 100 measurements (2.00%)
2 (2.00%) high mild
==48981==
==48981== Events : Ir Bc Bcm Bi Bim
==48981== Collected : 4275699913 515214573 26957819 3927787 16825
==48981==
==48981== I refs: 4,275,699,913
==48981==
==48981== Branches: 519,142,360 (515,214,573 cond + 3,927,787 ind)
==48981== Mispredicts: 26,974,644 ( 26,957,819 cond + 16,825 ind)
==48981== Mispred rate: 5.2% ( 5.2% + 0.4% )
```
</p>
</details>
<details>
<summary>perf -e result</summary>
<p>
current branch
```
Performance counter stats for './variant_cast_cast_kernels-589283a85a93d289 --bench cast decimal32 to uint8':
28594921663 cycles:u # 2.495 GHz
<not supported> instructions:u
<not supported> cache-references:u
<not supported> cache-misses:u
<not supported> branch-misses:u
11461.11 msec cpu-clock:u # 0.998 CPUs utilized
11461.12 msec task-clock:u # 0.998 CPUs utilized
11.479687283 seconds time elapsed
11.462746000 seconds user
0.000000000 seconds sys
```
main branch
```
[ec2-user@ip-172-31-35-37 ~]$ perf stat -e cycles,instructions,cache-references,cache-misses,branch-misses,cpu-clock,task-clock -- ./main_cast_kernels-589283a85a93d289 --bench "cast decimal32 to uint8"
"cast decimal32 to uint8"
time: [86.483 µs 86.859 µs 87.249 µs]
change: [+1.3885% +1.9087% +2.4051%] (p = 0.00 < 0.05)
Performance has regressed.
Found 3 outliers among 100 measurements (3.00%)
3 (3.00%) high mild
Performance counter stats for './main_cast_kernels-589283a85a93d289 --bench cast decimal32 to uint8':
29326652377 cycles:u # 2.424 GHz
<not supported> instructions:u
<not supported> cache-references:u
<not supported> cache-misses:u
<not supported> branch-misses:u
12096.47 msec cpu-clock:u # 1.000 CPUs utilized
12096.48 msec task-clock:u # 1.000 CPUs utilized
12.100896685 seconds time elapsed
12.087933000 seconds user
0.009998000 seconds sys
```
</p>
</details>
<details>
<summary>cpu details(lscpu)</summary>
```
Architecture: aarch64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 2
On-line CPU(s) list: 0,1
Vendor ID: ARM
Model name: Neoverse-N1
Model: 1
Thread(s) per core: 1
Core(s) per socket: 2
Socket(s): 1
Stepping: r3p1
BogoMIPS: 243.75
Flags: fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm lrcpc dcpop asimddp
Caches (sum of all):
L1d: 128 KiB (2 instances)
L1i: 128 KiB (2 instances)
L2: 2 MiB (2 instances)
L3: 32 MiB (1 instance)
NUMA:
NUMA node(s): 1
NUMA node0 CPU(s): 0,1
Vulnerabilities:
Gather data sampling: Not affected
Indirect target selection: Not affected
Itlb multihit: Not affected
L1tf: Not affected
Mds: Not affected
Meltdown: Not affected
Mmio stale data: Not affected
Reg file data sampling: Not affected
Retbleed: Not affected
Spec rstack overflow: Not affected
Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl
Spectre v1: Mitigation; __user pointer sanitization
Spectre v2: Mitigation; CSV2, BHB
Srbds: Not affected
Tsa: Not affected
Tsx async abort: Not affected
Vmscape: Not affected
```
</details>
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