On 08/07/2014 07:05 AM, Christian Lamparter wrote:

The high overhead (math_state_restore and fpu_save_init) are caused by 
the way ccm.c interacts with the aesni implementation when calculating
the MAC [1] (in compute_mac). 

quoted

   [ ... ]
	/* now encrypt rest of data */
	while (datalen >= 16) {
		crypto_xor(odata, data, bs);
		crypto_cipher_encrypt_one(tfm, odata, odata);

		datalen -= 16;
		data += 16;
	}
  [...]

crypto_cipher_encrypt_one is a wrapper which in your case calls 
aesni's aes_encrypt [2].

And aes_encrypt looks like this: 

quoted

	[...]
	kernel_fpu_begin();
	aesni_enc(ctx, dst, src); <-- this is where it goes to _aesni_enc1
	kernel_fpu_end();
	[...] 

Or: for every 16 Bytes of payload there is one fpu context save and
restore... ouch!

I have never messed with this kind of stuff...

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?

Thanks,
Ben

-- 
Ben Greear [off-list ref]
Candela Technologies Inc  http://www.candelatech.com