| From: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
|---|---|
| To: | Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com> |
| Cc: | Peter Eisentraut <peter(at)eisentraut(dot)org>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: define pg_structiszero(addr, s, r) |
| Date: | 2024-10-29 09:39:03 |
| Message-ID: | 2ed3e31e-55ee-41f6-8841-b096a798f504@iki.fi |
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| Lists: | pgsql-hackers |
On 29/10/2024 09:54, Bertrand Drouvot wrote:
>> https://godbolt.org/z/x9hPWjheq.
>
> Yeah, I also think that's fine. Peter Smith did some testing in [1] comparing
> memcmp and simple loop checking (thanks Peter for the testing!):
>
> "
> Iterate 1000000 times...
> check zeros using loop -- elapsed=0.041196s
> check zeros using memcmp -- elapsed=0.016407s
> "
>
> So, in this test, the loop is 0.024789s longer means 0.024789s/1000000=24 Nanosecond
> slower per comparison (If my math is correct).
I believe that test program is bogus. Look at the assembly code; the
compiler optimized away the loops.
--
Heikki Linnakangas
Neon (https://neon.tech)
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