linux-kernel - Re: [PATCH] crypto: xor - fix template benchmarking

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Date: Fri, 28 Jun 2024 11:03:58 +1000
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Helge Deller <deller@...nel.org>
Cc: linux-crypto@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
	linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: xor - fix template benchmarking

On Wed, Jun 19, 2024 at 07:31:57PM +0200, Helge Deller wrote:
> Commit c055e3eae0f1 ("crypto: xor - use ktime for template benchmarking")
> switched from using jiffies to ktime-based performance benchmarking.
> 
> This works nicely on machines which have a fine-grained ktime()
> clocksource as e.g. x86 machoines with TSC.
> But other machines, e.g. my 4-way HP PARISC server, don't have such
> fine-grained clocksources, which is why it seems that 800 xor loops
> take zero seconds, which then calculates in the logs as:
> 
>  xor: measuring software checksum speed
>     8regs           : -1018167296 MB/sec
>     8regs_prefetch  : -1018167296 MB/sec
>     32regs          : -1018167296 MB/sec
>     32regs_prefetch : -1018167296 MB/sec

Ard, could you please take a look at this patch when you get a
chance? Thanks!
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt