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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Tue, 4 Aug 2020 15:08:59 +0200
Message-ID: <CAMj1kXFnfYKj1JE4NLsxXtaeKuAOKyBYDbayLr-mHDUYqnV1bA@mail.gmail.com>
Subject: Re: [PATCH] crypto: x86/aesni - implement accelerated CBCMAC, CMAC
 and XCBC shashes
To:     Ben Greear <greearb@candelatech.com>
Cc:     Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Eric Biggers <ebiggers@kernel.org>
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On Tue, 4 Aug 2020 at 15:01, Ben Greear <greearb@candelatech.com> wrote:
>
> On 8/4/20 5:55 AM, Ard Biesheuvel wrote:
> > On Mon, 3 Aug 2020 at 21:11, Ben Greear <greearb@candelatech.com> wrote:
> >>
> >> Hello,
> >>
> >> This helps a bit...now download sw-crypt performance is about 150Mbps,
> >> but still not as good as with my patch on 5.4 kernel, and fpu is still
> >> high in perf top:
> >>
> >>      13.89%  libc-2.29.so   [.] __memset_sse2_unaligned_erms
> >>        6.62%  [kernel]       [k] kernel_fpu_begin
> >>        4.14%  [kernel]       [k] _aesni_enc1
> >>        2.06%  [kernel]       [k] __crypto_xor
> >>        1.95%  [kernel]       [k] copy_user_generic_string
> >>        1.93%  libjvm.so      [.] SpinPause
> >>        1.01%  [kernel]       [k] aesni_encrypt
> >>        0.98%  [kernel]       [k] crypto_ctr_crypt
> >>        0.93%  [kernel]       [k] udp_sendmsg
> >>        0.78%  [kernel]       [k] crypto_inc
> >>        0.74%  [kernel]       [k] __ip_append_data.isra.53
> >>        0.65%  [kernel]       [k] aesni_cbc_enc
> >>        0.64%  [kernel]       [k] __dev_queue_xmit
> >>        0.62%  [kernel]       [k] ipt_do_table
> >>        0.62%  [kernel]       [k] igb_xmit_frame_ring
> >>        0.59%  [kernel]       [k] ip_route_output_key_hash_rcu
> >>        0.57%  [kernel]       [k] memcpy
> >>        0.57%  libjvm.so      [.] InstanceKlass::oop_follow_contents
> >>        0.56%  [kernel]       [k] irq_fpu_usable
> >>        0.56%  [kernel]       [k] mac_do_update
> >>
> >> If you'd like help setting up a test rig and have an ath10k pcie NIC or ath9k pcie NIC,
> >> then I can help.  Possibly hwsim would also be a good test case, but I have not tried
> >> that.
> >>
> >
> > I don't think this is likely to be reproducible on other
> > micro-architectures, so setting up a test rig is unlikely to help.
> >
> > I'll send out a v2 which implements a ahash instead of a shash (and
> > implements some other tweaks) so that kernel_fpu_begin() is only
> > called twice for each packet on the cbcmac path.
> >
> > Do you have any numbers for the old kernel without your patch? This
> > pathological FPU preserve/restore behavior could be caused be the
> > optimizations, or by other changes that landed in the meantime, so I
> > would like to know if kernel_fpu_begin() is as prominent in those
> > traces as well.
> >
>
> This same patch makes i7 mobile processors able to handle 1Gbps+ software
> decrypt rates, where without the patch, the rate was badly constrained and CPU
> load was much higher, so it is definitely noticeable on other processors too.

OK

> The weak processor on the current test rig is convenient because the problem
> is so noticeable even at slower wifi speeds.
>
> We can do some tests on 5.4 with our patch reverted.
>

The issue with your CCM patch is that it keeps the FPU enabled for the
entire input, which also means that preemption is disabled, which
makes the -rt people grumpy. (Of course, it also uses APIs that no
longer exists, but that should be easy to fix)

Do you happen to have any ballpark figures for the packet sizes and
the time spent doing encryption?