| From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
|---|---|
| To: | "Chiranmoy(dot)Bhattacharya(at)fujitsu(dot)com" <Chiranmoy(dot)Bhattacharya(at)fujitsu(dot)com> |
| Cc: | "Malladi, Rama" <ramamalladi(at)hotmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, "Ragesh(dot)Hajela(at)fujitsu(dot)com" <Ragesh(dot)Hajela(at)fujitsu(dot)com>, Salvatore Dipietro <dipiets(at)amazon(dot)com>, "Devanga(dot)Susmitha(at)fujitsu(dot)com" <Devanga(dot)Susmitha(at)fujitsu(dot)com> |
| Subject: | Re: [PATCH] SVE popcount support |
| Date: | 2025-02-06 16:33:35 |
| Message-ID: | Z6TkX1Uo3kxeUlKp@nathan |
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| Lists: | pgsql-hackers |
On Thu, Feb 06, 2025 at 08:44:35AM +0000, Chiranmoy(dot)Bhattacharya(at)fujitsu(dot)com wrote:
>> Does this hand-rolled loop unrolling offer any particular advantage? What
>> do the numbers look like if we don't do this or if we process, say, 4
>> vectors at a time?
>
> The unrolled version performs better than the non-unrolled one, but
> processing four vectors provides no additional benefit. The numbers
> and code used are given below.
Hm. Any idea why that is? I wonder if the compiler isn't using as many
SVE registers as it could for this.
--
nathan
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