From: Eric Biggers <ebiggers@kernel.org>
To: Antonio Quartulli <antonio@mandelbit.com>
Cc: linux-crypto@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
"Jason A . Donenfeld" <Jason@zx2c4.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
Martin Willi <martin@strongswan.org>
Subject: Re: [PATCH] lib/crypto: x86/chacha: Eliminate more never-taken branches
Date: Thu, 5 Nov 2026 19:08:33 +0000 [thread overview]
Message-ID: <20261105190833.GA3266627@google.com> (raw)
In-Reply-To: <3349b575-5f1d-4b81-be15-5f92565904e7@mandelbit.com>
On Thu, Nov 05, 2026 at 04:31:41PM +0100, Antonio Quartulli wrote:
> path CPU setup KUnit perf
> ------------------- --------------------- ----- ------------
> AVX-512, zmm native pass -1.0..-0.1%
[...]
> There is a little loss in the zmm case. I presume we can live with that, but
> was worth mentioning.
Probably just noise, or maybe instruction alignment which is best
tweaked separately if needed rather than relying on chance.
Note that removing these branches will help mostly if the caches
(instruction cache and branch predictor) are cold, which the benchmark
doesn't measure. We maybe should start trying to measure the cold cache
case in the lib/crypto/ benchmarks, as it is meaningful too.
- Eric
next prev parent reply other threads:[~2026-11-05 19:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-04 22:55 [PATCH] lib/crypto: x86/chacha: Eliminate more never-taken branches Eric Biggers
2026-11-05 15:31 ` Antonio Quartulli
2026-11-05 19:08 ` Eric Biggers [this message]
2026-11-05 20:06 ` Antonio Quartulli
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