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From: Amonson, Paul D <[email protected]>
To: Nathan Bossart <[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: Tom Lane <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Cc: [email protected] <[email protected]>
Subject: RE: Popcount optimization using AVX512
Date: Mon, 18 Mar 2024 17:28:32 +0000
Message-ID: <BL1PR11MB5304552343DD5E6DDD27A672DC2D2@BL1PR11MB5304.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20240318162018.GA204772@nathanxps13>
References: <BL1PR11MB530444AEE08A91242ABA1915DC222@BL1PR11MB5304.namprd11.prod.outlook.com>
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	<BL1PR11MB5304165E7A81E0107E70B069DC242@BL1PR11MB5304.namprd11.prod.outlook.com>
	<20240312013436.GA1787866@nathanxps13>
	<BL1PR11MB53042473B7B53B96E43648A7DC292@BL1PR11MB5304.namprd11.prod.outlook.com>
	<20240315150611.GA3495582@nathanxps13>
	<CAApHDvrb7MJRB6JuKLDEY2x_LKdFHwVbogpjZBCX547i5+rXOQ@mail.gmail.com>
	<20240318152902.GA2850@nathanxps13>
	<BL1PR11MB5304070E33F7DD0520445B77DC2D2@BL1PR11MB5304.namprd11.prod.outlook.com>
	<20240318162018.GA204772@nathanxps13>

> -----Original Message-----
> From: Nathan Bossart <[email protected]>
> Sent: Monday, March 18, 2024 9:20 AM
> ...
> I don't think David was suggesting that we need to remove the runtime checks
> for AVX512.  IIUC he was pointing out that most of the performance gain is
> from removing the function call overhead, which your v8-0002 patch already
> does for the proposed AVX512 code.  We can apply a similar optimization for
> systems without AVX512 by inlining the code for
> pg_popcount64() and pg_popcount32().

Ok, got you.

Question: I applied the patch for the drive_popcount* functions and rebuilt.  The resultant server complains that the function is missing. What is the trick to make this work?

Another Question: Is there a reason "time psql" is used over the Postgres "\timing" command?

Thanks,
Paul

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