crypto: talitos - chain in buffered data for ahash on SEC1
SEC1 doesn't support S/G in descriptors so for hash operations,
the CPU has to build a buffer containing the buffered block and
the incoming data. This generates a lot of memory copies which
represents more than 50% of CPU time of a md5sum operation as
shown below with a 'perf record'.
However, unlike SEC2+, SEC1 offers the possibility to chain
descriptors. It is therefore possible to build a first descriptor
pointing to the buffered data and a second descriptor pointing to
the incoming data, hence avoiding the memory copy to a single
buffer.
With this patch, the time necessary for a md5sum on a 90Mbytes file
is approximately 3 seconds. Without the patch it takes 6 seconds.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>