linux-kernel - Re: [PATCH 00/12] x86/crypto: Fix RBP usage in several crypto .S files

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Message-ID: <20170908175705.GA623@zzz.localdomain>
Date:   Fri, 8 Sep 2017 10:57:05 -0700
From:   Eric Biggers <ebiggers3@...il.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Mathias Krause <minipli@...glemail.com>,
        Chandramouli Narayanan <mouli@...ux.intel.com>,
        Jussi Kivilinna <jussi.kivilinna@....fi>,
        Peter Zijlstra <peterz@...radead.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, Eric Biggers <ebiggers@...gle.com>,
        Andy Lutomirski <luto@...nel.org>, Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH 00/12] x86/crypto: Fix RBP usage in several crypto .S
 files

On Thu, Sep 07, 2017 at 11:26:47PM +0200, Ingo Molnar wrote:
> 
> * Eric Biggers <ebiggers3@...il.com> wrote:
> 
> > On Thu, Sep 07, 2017 at 09:15:34AM +0200, Ingo Molnar wrote:
> > > 
> > > * Eric Biggers <ebiggers3@...il.com> wrote:
> > > 
> > > > Thanks for fixing these!  I don't have time to review these in detail, but I ran
> > > > the crypto self-tests on the affected algorithms, and they all pass.  I also
> > > > benchmarked them before and after; the only noticable performance difference was
> > > > that sha256-avx2 and sha512-avx2 became a few percent slower.  I don't suppose
> > > > there is a way around that?  Otherwise it's probably not a big deal.
> > > 
> > > Which CPU model did you use for the test?
> > > 
> > > Thanks,
> > > 
> > > 	Ingo
> > 
> > This was on Haswell, "Intel(R) Xeon(R) CPU E5-1650 v3 @ 3.50GHz".
> 
> Any chance to test this with the latest microarchitecture - any Skylake derivative 
> Intel CPU you have access to?
> 
> Thanks,
> 
> 	Ingo

Tested with Skylake, "Intel(R) Core(TM) i5-6200U CPU @ 2.30GHz".  The results
were the following which seemed a bit worse than Haswell:

	sha256-avx2 became 3.5% slower
	sha512-avx2 became 7.5% slower

Note: it's tricky to benchmark this, especially with just a few percent
difference, so don't read too much into the exact numbers.

Eric