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From:   Gilad Ben-Yossef <gilad@benyossef.com>
Date:   Sun, 6 Jun 2021 09:49:47 +0300
Message-ID: <CAOtvUMf3r0oT6w=mgQyykX_RHDDmebm_q-TqV61jSmo5x0bweQ@mail.gmail.com>
Subject: Re: Qualcomm Crypto Engine performance numbers on mainline kernel
To:     Ard Biesheuvel <ardb@kernel.org>
Cc:     Thara Gopinath <thara.gopinath@linaro.org>,
        Eric Biggers <ebiggers@kernel.org>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>
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Hi,

On Sat, Jun 5, 2021 at 6:33 PM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> Hello Thara,
>
> On Fri, 4 Jun 2021 at 18:49, Thara Gopinath <thara.gopinath@linaro.org> w=
rote:
> >
> >
> > Hi All,
> >
> > Below are the performance numbers from running "crypsetup benchmark" on
> > CE algorithms in the mainline kernel. All numbers are in MiB/s. The
> > platform used is RB3 for sdm845 and MTPs for rest of them.
> >
> >
> >                         SDM845    SM8150     SM8250     SM8350
> > AES-CBC (128)
> > Encrypt / Decrypt       114/106  36/48       120/188    133/197
> >
> > AES-XTS (256)
> > Encrypt / Decrypt       100/102  49/48       186/187    n/a
> >
>
> The CPU instruction based ones are apparently an order of magnitude
> faster, and are synchronous so their latency should be lower.
>
> So, as Eric already pointed out IIRC, there doesn't seem to be much
> value in enabling this IP in Linux - it should not be the default
> choice/highest priority, and it is not obvious to me whether/when you
> would prefer this implementation over the CPU based one. Do you have
> any idea how many queues it has, or how much data it can process in
> parallel? Are there other features that stand out?

One of the things to consider with separate hardware block
implementation vis a vis CPU instruction based ones in general is that
often the consideration is more about getting a good enough
performance while freeing the CPU to perform other tasks which results
in better overall system performance rather than getting the best
possible performance in the specific task at hand. This is sometimes
further extended with power considerations where you can get better
power consumption when the lower performance  engine is used.
Less often, a lower jitter is more important than the peak
performance. I've seen this with encrypted video decoding for example.

Sadly, whether any of these considerations is applicable is very much
system and work load specific.

So my 2c contribution would be to include support for this, even if
not make this the default.

Gilad


--=20
Gilad Ben-Yossef
Chief Coffee Drinker

values of =CE=B2 will give rise to dom!