Hi again,
On Wed, Dec 14, 2016 at 5:37 PM, Theodore Ts'o <tytso@xxxxxxx> wrote:
> [ 3.606139] random benchmark!!
> [ 3.606276] get_random_int # cycles: 326578
> [ 3.606317] get_random_int_new # cycles: 95438
> [ 3.607423] get_random_bytes # cycles: 2653388
Looks to me like my siphash implementation is much faster for
get_random_long, and more or less tied for get_random_int:
[ 1.729370] random benchmark!!
[ 1.729710] get_random_long # cycles: 349771
[ 1.730128] get_random_long_chacha # cycles: 359660
[ 1.730457] get_random_long_siphash # cycles: 94255
[ 1.731307] get_random_bytes # cycles: 1354894
[ 1.731707] get_random_int # cycles: 305640
[ 1.732095] get_random_int_chacha # cycles: 80726
[ 1.732425] get_random_int_siphash # cycles: 94265
[ 1.733278] get_random_bytes # cycles: 1315873
Given the increasing usage of get_random_long for ASLR and related, I
think this makes the siphash approach worth pursuing. The chacha
approach is also not significantly different from the md5 approach in
terms of speed for get_rand_long. Additionally, since siphash is a
PRF, I think this opens up a big window for optimizing it even
further.
Benchmark here:
https://git.zx2c4.com/linux-dev/commit/?h=rng-bench
Jason
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