Adding encryption to Btrfs [LWN.net]

Adding encryption to Btrfs

Posted Sep 23, 2016 16:15 UTC (Fri) by magila (guest, #49627)
In reply to: Adding encryption to Btrfs by epa
Parent article: Adding encryption to Btrfs

Even on larger CPUs hardware AES is more power efficient. The SIMD units are by far the most power hungry logic units in modern Intel CPUs.

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Adding encryption to Btrfs

Posted Sep 27, 2016 14:36 UTC (Tue) by jtaylor (subscriber, #91739) [Link] (1 responses)

I'm curious, do you have a source for that claim?

Adding encryption to Btrfs

Posted Sep 29, 2016 4:31 UTC (Thu) by magila (guest, #49627) [Link]

I'm not aware of any published comparisons. I've done some informal testing on my own machine, a quad core Skylake running at 4.5GHz, with 8K blocks and found:

ChaCha20 achieves 16.4GB/s while consuming 102W or 5.93 microjoules/byte
AES-128-CTR achieves 22.4 GB/s while consuming 87W or 3.70 microjoules/byte
AES-256-CTR achieves 16.6 GB/s while consuming 82W or 4.71 microjoules/byte

You might argue comparing AES-128 to ChaCha20 is unfair, but the fact is those are by far the most widely used variants of each.

ChaCha20 was tested using the benchmark tool from https://github.com/floodyberry/chacha-opt modified to run ChaCha20-avx2 with 8K blocks in a loop
AES was tested using the example code from https://wiki.openssl.org/index.php/EVP_Symmetric_Encrypti... modified to encrypt 8K blocks in a loop.
All tests were done with 4 instances running in parallel.
Power consumption was measured using CPUID HWMonitor.