[tor-relays] Info about HW Encryption on Raspberry

[Fr33d0m4all]

Hi,
I have a Raspberry Pi3 that runs a Tor mid-relay and I’ve noticed that in the last weeks it reaches high temperatures (about 76°C) due to high CPU usage when Tor traffic increases. It did not reach this temperature until this summer (but it is not due to an higher environment temperature), so I don’t know if it can be related to 0.3 version. Now I’m running Tor 0.3.1.7. Should Tor 0.3.x use Raspberry Pi3 AES-NI hardware acceleration to reduce high cpu usage? Is there a way to check and enable it if disabled?

# openssl speed -evp aes-256-cbc
Doing aes-256-cbc for 3s on 16 size blocks: 5560204 aes-256-cbc's in 3.00s
Doing aes-256-cbc for 3s on 64 size blocks: 1631984 aes-256-cbc's in 3.00s
Doing aes-256-cbc for 3s on 256 size blocks: 425826 aes-256-cbc's in 3.00s
Doing aes-256-cbc for 3s on 1024 size blocks: 107776 aes-256-cbc's in 3.00s
Doing aes-256-cbc for 3s on 8192 size blocks: 13489 aes-256-cbc's in 3.00s
OpenSSL 1.0.1t  3 May 2016
built on: Fri Jan 27 22:44:27 2017
options:bn(64,32) rc4(ptr,char) des(idx,cisc,16,long) aes(partial) blowfish(ptr)
compiler: gcc -I. -I.. -I../include  -fPIC -DOPENSSL_PIC -DOPENSSL_THREADS -D_REENTRANT -DDSO_DLFCN -DHAVE_DLFCN_H -DL_ENDIAN -DTERMIO -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2 -Wl,-z,relro -Wa,--noexecstack -Wall -DOPENSSL_BN_ASM_MONT -DOPENSSL_BN_ASM_GF2m -DSHA1_ASM -DSHA256_ASM -DSHA512_ASM -DAES_ASM -DGHASH_ASM
The 'numbers' are in 1000s of bytes per second processed.
type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes
aes-256-cbc      29654.42k    34815.66k    36337.15k    36787.54k    36833.96k

Best regards,
   Fr33d0m4All