Re: [RFC PATCH v4] IV Generation algorithms for dm-crypt

[Milan Broz <gmazyland@gmail.com>]

On 03/01/2017 02:04 PM, Milan Broz wrote:
> On 03/01/2017 01:42 PM, Gilad Ben-Yossef wrote:
> ...
> 
>> I can certainly understand if you don't wont to take the patch until
>> we have results with
>> dm-crypt itself but the difference between 8 separate invocation of
>> the engine for 512
>> bytes of XTS and a single invocation for 4KB are pretty big.
> 
> Yes, I know it. But the same can be achieved if we just implement
> 4k sector encryption in dmcrypt. It is incompatible with LUKS1
> (but next LUKS version will support it) but I think this is not
> a problem for now.
> 
> If the underlying device supports atomic write of 4k sectors, then
> there should not be a problem.
> 
> This is one of the speed-up I would like to compare with the IV approach,
> because everyone should benefit from 4k sectors in the end.
> And no crypto API changes are needed here.
> 
> (I have an old patch for this, so I will try to revive it.)

If anyone interested, simple experimental patch for larger sector size
(up to the page size) for dmcrypt is in this branch:

http://git.kernel.org/cgit/linux/kernel/git/mbroz/linux.git/log/?h=dm-crypt-4k-sector

It would be nice to check what performance gain could be provided
by this simple approach.

Milan