raid: R-V V pq_gen xor_gen #318
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hleft
commented
Mar 21, 2025
hleft
commented
banana_f3:
new: pq_gen_warm: runtime = 3062397 usecs, bandwidth 4737 MB in 3.0624 sec = 1546.92 MB/s
old: pq_gen_warm: runtime = 3005894 usecs, bandwidth 2851 MB in 3.0059 sec = 948.80 MB/s
Signed-off-by: sunyuechi <sunyuechi@iscas.ac.cn>
raid/raid_base.c
Outdated
| @@ -139,6 +139,6 @@ xor_check_base(int vects, int len, void **array) | |||
| } | |||
| } | |||
| if (fail && len > 0) | |||
| return len; | |||
| return (len % 256 == 0) ? 1 : len; | |||
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I don't quite understand this fix. "len" is an int, so it shouldn't return a 0 when len is multiple of 256. Said this, I have looked into the x86 and aarch64 implementations and both return a 1 when the check fails, so I'm inclined to change this to return 1 in case of failure here too.
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Manually setting the return value in the test program to 256, 512, etc., will still pass the test. I guess it's because POSIX specifies that the return value range is 0–255, so it's evaluated as (% 256) before checking whether it's zero.
Returning len or 1 should both be fine; it's just that the original intention might have been to preserve some information, so it wasn't changed.
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If SIMD uses empty code, make check will pass, but running raid/xor_check_test will result in an error and return 1024.
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I see... What do you mean about empty code? And also, why 1024?
I'd say we should then change the base function to return 1 in case of failure, so it is consistent with the other implementations.
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Before implementing the SIMD code, I wrote an empty assembly function that simply returns, and then ran make check, which passed. However, the raid/xor_check_test output was 1024 (because the TEST_LEN used in the test program is 1024), so I noticed the issue.
I've now updated it to return 1.
If len > 255, the return value will be % 256, which causes the test to incorrectly pass Signed-off-by: sunyuechi <sunyuechi@iscas.ac.cn>
banana_f3:
new: xor_gen_warm: runtime = 3006459 usecs, bandwidth 10685 MB in 3.0065 sec = 3554.17 MB/s
old: xor_gen_warm: runtime = 3060970 usecs, bandwidth 514 MB in 3.0610 sec = 168.21 MB/s
Signed-off-by: sunyuechi <sunyuechi@iscas.ac.cn>
