On 3 December 2015 at 23:47, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > On Thu, 3 Dec 2015, Baolin Wang wrote: > >> On 3 December 2015 at 03:56, Alasdair G Kergon <agk@xxxxxxxxxx> wrote: >> > On Wed, Dec 02, 2015 at 08:46:54PM +0800, Baolin Wang wrote: >> >> These are the benchmarks for request based dm-crypt. Please check it. >> > >> > Now please put request-based dm-crypt completely to one side and focus >> > just on the existing bio-based code. Why is it slower and what can be >> > adjusted to improve this? >> > >> >> OK. I think I find something need to be point out. >> 1. From the IO block size test in the performance report, for the >> request based, we can find it can not get the corresponding >> performance if we just expand the IO size. Because In dm crypt, it >> will map the data buffer of one request with scatterlists, and send >> all scatterlists of one request to the encryption engine to encrypt or >> decrypt. I found if the scatterlist list number is small and each >> scatterlist length is bigger, it will improve the encryption speed, > > This optimization is only applicable to XTS mode. XTS has its weaknesses > and it is not recommended for encryption of more than 1TB of data > ( http://grouper.ieee.org/groups/1619/email/msg02357.html ) > > You can optimize bio-based dm-crypt as well (use larger encryption chunk > than 512 bytes when the mode is XTS). > > The most commonly used mode aes-cbc-essiv:sha256 can't be optimized that > way. You have to do encryption and decryption sector by sector because > every sector has different IV. Make sense. We'll optimize bio-based dm-crypt for XTS mode, and do some investigations for none XTS mode. > > Mikulas > -- Baolin.wang Best Regards -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
