Commit Graph

2 Commits

Author SHA1 Message Date
Jakob Unterwurzacher
312ea32bb7 cryptocore: add urandom + randprefetch benchmarks
The benchmark that supported the decision for 512-byte
prefetching previously lived outside the repo.

Let's add it where it belongs so it cannot get lost.
2017-08-16 18:33:00 +02:00
Jakob Unterwurzacher
80516ed335 cryptocore: prefetch nonces in 512-byte blocks
On my machine, reading 512-byte blocks from /dev/urandom
(same via getentropy syscall) is a lot faster in terms of
throughput:

Blocksize    Throughput
 16          28.18 MB/s
512          83.75 MB/s

For a single-threaded streaming write, this drops the CPU usage of
nonceGenerator.Get to almost 1/3:

        flat  flat%   sum%        cum   cum%
Before     0     0% 95.08%      0.35s  2.92%  github.com/rfjakob/gocryptfs/internal/cryptocore.(*nonceGenerator).Get
After  0.01s 0.092% 92.34%      0.13s  1.20%  github.com/rfjakob/gocryptfs/internal/cryptocore.(*nonceGenerator).Get

This change makes the nonce reading single-threaded, which may
hurt massively-parallel writes.
2017-06-09 22:05:14 +02:00