Hi Geert, On Thu, Jul 19, 2018 at 3:43 PM, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > Hi Gilad, > > I've noticed CCREE is used with a LUKS-formatted disk, so I did some small > performance benchmarks. The disk is an old 160 GiB SATA hard drive, > connected to either Salvator-XS (R-Car H3 ES2.0) or Koelsch (R-Car M2-W). > > hdparm -t /dev/sda (unencrypted data): 62 MB/s (both systems) > > hdparm -t /dev/dm-0 (encrypted data, LUKS AES): > > salvator-xs (CCREE): 15 MB/s > salvator-xs (SW): 62 MB/s > koelsch (SW): 47 MB/s > > I'm a bit disappointment by the results when using crypto acceleration. > Apparently the in-kernel optimized arm64 implementation can decrypt at > raw read speed, while CCREE can't keep up. Interesting. What is the encryption sector size used? If it is he default of 512 bytes, you might want to try setting the new block_size DM-Crypt option. I believe it will have a large effect on the result. > Is this expected, and in line with your experiences? Well, if you were indeed using the default 512 bytes and taking into account that sadly the CryptoCell inside the R-Car is not wired to utilize a coherent bus (the cache invalidation costs a fortune in performance) it is not unexpected. When reasoning about these things it is worth taking into account that the design target of using CryptoCell is not to get the absolute best raw performance as such but rather to get good performance / per cycle / per watt. When the Arm AES Crypto Extension is used (I assume you are using that and not, say, the NEON implementation) I expect the raw performance to always be better than CryptoCell, certainly when it is not attached to a coherent bus. However, if you check CPU utilization during the operation (basically how much encryption is "stealing" computation power from the CPU) and subsequent power consumption you are supposed to see that there is a large area of work loads where it makes more sense to utilize CryptoCell for disk encryption and use the CPU for something else. ... in theory, at least. :-) We've just in the middle of an office move here, but I hope things will settle down during the ween and I'll be able to replicate your test and see if I can advise better, but certainly using 4k encryption section size is key, otherwise the overhead just kills everything. Thanks! Gilad -- Gilad Ben-Yossef Chief Coffee Drinker values of β will give rise to dom!
