From: Christian Lamparter <chunkeey@googlemail.com>
To: Ben Greear <greearb@candelatech.com>
Cc: Jouni Malinen <j@w1.fi>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
	Johannes Berg <johannes@sipsolutions.net>
Subject: Re: Looking for non-NIC hardware-offload for wpa2 decrypt.
Date: Thu, 14 Aug 2014 14:39:04 +0200
Message-ID: <8289144.MKHmP0uSFO@debian64> (sfid-20140814_143918_803535_B3F720C1)
In-Reply-To: <53EA5E53.9010704@candelatech.com>
References: <5338F1B8.5040305@candelatech.com> <1518134.xFh23iA8q1@blech> <53EA5E53.9010704@candelatech.com>
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Sender: linux-wireless-owner@vger.kernel.org

On Tuesday, August 12, 2014 11:34:59 AM Ben Greear wrote:
> On 08/10/2014 06:44 AM, Christian Lamparter wrote:
> > On Thursday, August 07, 2014 10:45:01 AM Ben Greear wrote:
> >> On 08/07/2014 07:05 AM, Christian Lamparter wrote:
> >>> Or: for every 16 Bytes of payload there is one fpu context save and
> >>> restore... ouch!
> >>
> >> Any idea if it would work to put the fpu_begin/end a bit higher
> >> and do all those 16 byte chunks in a batch without messing with
> >> the FPU for each chunk?
> > 
> > It sort of works - see sample feature patch for aesni-intel-glue 
> > (taken from 3.16-wl). Older kernels (like 3.15, 3.14) need:
> > "crypto: allow blkcipher walks over AEAD data" [0] (and maybe more).
> > 
> > The FPU save/restore overhead should be gone. Also, if the aesni
> > instructions can't be used, the implementation will fall back
> > to the original ccm(aes) code. Calculating the MAC is still much
> > more expensive than the payload encryption or decryption. However,
> > I can't see a way of making this more efficient without rewriting
> > and combining the parts I took from crypto/ccm.c into an several, 
> > dedicated assembler functions.
> 
> Without encryption, I see download rate of around 400 - 420Mbps.
>
> So, your patch looks like a good improvement to me, and I'll be
> happy to test further patches if you happen to do those assembler
> optimizations you talk about above.

Maybe, that will depend on what the results for: "wpa2, *HW*-crypt,
download, udp" are.

> Let me know if you would like more/different performance
> stats. 

There's a test bench tool (tcrypt) to measure the performance 
of any cipher. It would be interesting to know what the 
performance/throughput it can produce without the overhead
of any application. [Yep, I'm making a small patch to test that,
but not before Saturday next week].
  
> Here is perf top of open authentication, download, UDP:
> 
> Using WPA2, sw-crypt, download, UDP:
> 
> Samples: 52K of event 'cycles', Event count (approx.): 13162827574
>  24.78%  btserver              [.] 0x00000000000c598c
Is btserver your "udp download" test application? What does it do, as
it is accounting for nearly 25%?

Regards
Christian