On Tue, Nov 03, 2020 at 05:28:09PM +0100, Ard Biesheuvel wrote: > The current NEON based ChaCha implementation for ARM is optimized for > multiples of 4x the ChaCha block size (64 bytes). This makes sense for > block encryption, but given that ChaCha is also often used in the > context of networking, it makes sense to consider arbitrary length > inputs as well. > > For example, WireGuard typically uses 1420 byte packets, and performing > ChaCha encryption involves 5 invocations of chacha_4block_xor_neon() > and 3 invocations of chacha_block_xor_neon(), where the last one also > involves a memcpy() using a buffer on the stack to process the final > chunk of 1420 % 64 == 12 bytes. > > Let's optimize for this case as well, by letting chacha_4block_xor_neon() > deal with any input size between 64 and 256 bytes, using NEON permutation > instructions and overlapping loads and stores. This way, the 140 byte > tail of a 1420 byte input buffer can simply be processed in one go. > > This results in the following performance improvements for 1420 byte > blocks, without significant impact on power-of-2 input sizes. (Note > that Raspberry Pi is widely used in combination with a 32-bit kernel, > even though the core is 64-bit capable) > > Cortex-A8 (BeagleBone) : 7% > Cortex-A15 (Calxeda Midway) : 21% > Cortex-A53 (Raspberry Pi 3) : 3% > Cortex-A72 (Raspberry Pi 4) : 19% > > Cc: Eric Biggers <ebiggers@xxxxxxxxxx> > Cc: "Jason A . Donenfeld" <Jason@xxxxxxxxx> > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > --- > v2: > - avoid memcpy() if the residual byte count is exactly 64 bytes > - get rid of register based post increments, and simply rewind the src > pointer as needed (the dst pointer did not need the register post > increment in the first place) > - add benchmark results for 32-bit CPUs to commit log. > > arch/arm/crypto/chacha-glue.c | 34 +++---- > arch/arm/crypto/chacha-neon-core.S | 97 ++++++++++++++++++-- > 2 files changed, 107 insertions(+), 24 deletions(-) Patch applied. Thanks. -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
