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Re: Prefetches in buffer_zero_*

From: Richard Henderson
Subject: Re: Prefetches in buffer_zero_*
Date: Thu, 22 Jul 2021 08:53:17 -1000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0

On 7/22/21 12:02 AM, Dr. David Alan Gilbert wrote:
Hi Richard,
   I think you were the last person to fiddle with the prefetching
in buffer_zero_avx2 and friends; Joe (cc'd) wondered if explicit
prefetching still made sense on modern CPUs, and that their hardware
generally figures stuff out better on simple increments.

   What was your thinking on this, and did you actually measure
any improvement?

Ah, well, that was 5 years ago so I have no particular memory of this. It wouldn't surprise me if you can't measure any improvement on modern hardware.

Do you now measure an improvement with the prefetches gone?


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