public inbox for [email protected]
help / color / mirror / Atom feedFrom: Nathan Bossart <[email protected]>
To: Amonson, Paul D <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: David Rowley <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Alvaro Herrera <[email protected]>
Cc: Shankaran, Akash <[email protected]>
Cc: Noah Misch <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: Popcount optimization using AVX512
Date: Thu, 28 Mar 2024 16:51:36 -0500
Message-ID: <20240328215136.GA918358@nathanxps13> (raw)
In-Reply-To: <20240328213854.GA916732@nathanxps13>
References: <CAApHDvrf-oKJ-mCrFZ_g-fZpRrCXJrKcZobwtUgzi0R5aXtVxQ@mail.gmail.com>
<BL1PR11MB530478ACABE588A836338E74DC322@BL1PR11MB5304.namprd11.prod.outlook.com>
<BL1PR11MB53040D8E18518B2BDA4BB83ADC362@BL1PR11MB5304.namprd11.prod.outlook.com>
<[email protected]>
<BL1PR11MB53043014C10F2D30B4231F9ADC362@BL1PR11MB5304.namprd11.prod.outlook.com>
<BL1PR11MB53049F1796E834DBE0E05864DC362@BL1PR11MB5304.namprd11.prod.outlook.com>
<20240325200551.GB2924132@nathanxps13>
<20240327220010.GA231058@nathanxps13>
<BL1PR11MB53047289F146DB43C9B2FC71DC342@BL1PR11MB5304.namprd11.prod.outlook.com>
<20240328213854.GA916732@nathanxps13>
On Thu, Mar 28, 2024 at 04:38:54PM -0500, Nathan Bossart wrote:
> Here is a v14 of the patch that I think is beginning to approach something
> committable. Besides general review and testing, there are two things that
> I'd like to bring up:
>
> * The latest patch set from Paul Amonson appeared to support MSVC in the
> meson build, but not the autoconf one. I don't have much expertise here,
> so the v14 patch doesn't have any autoconf/meson support for MSVC, which
> I thought might be okay for now. IIUC we assume that 64-bit/MSVC builds
> can always compile the x86_64 popcount code, but I don't know whether
> that's safe for AVX512.
>
> * I think we need to verify there isn't a huge performance regression for
> smaller arrays. IIUC those will still require an AVX512 instruction or
> two as well as a function call, which might add some noticeable overhead.
I forgot to mention that I also want to understand whether we can actually
assume availability of XGETBV when CPUID says we support AVX512:
> + /*
> + * We also need to check that the OS has enabled support for the ZMM
> + * registers.
> + */
> +#ifdef _MSC_VER
> + return (_xgetbv(0) & 0xe0) != 0;
> +#else
> + uint64 xcr = 0;
> + uint32 high;
> + uint32 low;
> +
> +__asm__ __volatile__(" xgetbv\n":"=a"(low), "=d"(high):"c"(xcr));
> + return (low & 0xe0) != 0;
> +#endif
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
view thread (5+ messages)
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
Subject: Re: Popcount optimization using AVX512
In-Reply-To: <20240328215136.GA918358@nathanxps13>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox