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| author | LEROY Christophe <christophe.leroy@c-s.fr> | 2017-10-06 15:05:06 +0200 |
|---|---|---|
| committer | Herbert Xu <herbert@gondor.apana.org.au> | 2017-10-12 22:55:38 +0800 |
| commit | 37b5e8897eb588a60dada00c33d2dca8a7fec5fc (patch) | |
| tree | fd0857a52821879b3cb3fca935072865139cc4dd /drivers/vhost | |
| parent | 49f9783b0cea9a4e38fdbfe70ca296e6f20914c4 (diff) | |
| download | linux-37b5e8897eb588a60dada00c33d2dca8a7fec5fc.tar.bz2 | |
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'.
|--86.24%-- kcapi_md_digest
| |
| |--86.18%-- _kcapi_common_vmsplice_chunk_fd
| | |
| | |--83.68%-- splice
| | | |
| | | |--83.59%-- ret_from_syscall
| | | | |
| | | | |--83.52%-- sys_splice
| | | | | |
| | | | | |--83.49%-- splice_from_pipe
| | | | | | |
| | | | | | |--83.04%-- __splice_from_pipe
| | | | | | | |
| | | | | | | |--80.67%-- pipe_to_sendpage
| | | | | | | | |
| | | | | | | | |--78.25%-- hash_sendpage
| | | | | | | | | |
| | | | | | | | | |--60.08%-- ahash_process_req
| | | | | | | | | | |
| | | | | | | | | | |--56.36%-- sg_copy_buffer
| | | | | | | | | | | |
| | | | | | | | | | | |--55.29%-- memcpy
| | | | | | | | | | | |
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>
Diffstat (limited to 'drivers/vhost')
0 files changed, 0 insertions, 0 deletions