Re: How to estimate the upper bound of the peak memory consumption of cryptsetup itself?

[Milan Broz <gmazyland@gmail.com>]

On 16/06/2022 06:43, Coiby Xu wrote:
> Hi,
> 
> Recently, I notice cryptsetup itself consumes significant amount of
> memory (~256M) when estimating the memory requirement for dumping vmcore
> to a LUKS-encrypted disk,
> 
> $ time -v cryptsetup luksOpen encrypted.img volume --key-file mykey.keyfile | grep "Maximum resident set size"
>           Maximum resident set size (kbytes): 1309828
> $ cryptsetup luksDump encrypted.img
> ...
> Keyslots:
>     0: luks2
>           PBKDF:      argon2id
>           Memory:     1048576
>           ...
> 
> 
> So is there a way to estimate the upper bound of the peak memory
> consumption of cryptsetup itself without running cryptsetup?

As you already found, the major memory consumption is by memory-hard KDF.
But this memory is used only while calculating keyslot encryption key,
it is released immediately after the Argon call is finished.
I do not think we have better estimation here.

(Another story is locking all memory, including big areas used by libc,
but that should not be problem here, I hope.)

Milan