Re: [PATCH 2/2] Include the memory overhead cost of cryptsetup when estimating the memory requirement for LUKS-encrypted target

[Philipp Rudo]

Hi Coiby,

On Mon,  5 Sep 2022 18:24:37 +0800
Coiby Xu <coxu(a)redhat.com&gt; wrote:

>  Currently, "kdumpctl estimate" neglects the memory overhead
> cost of
>  cryptsetup itself. Unfortunately, there is no golden formula to
>  calculate the overhead cost [1]. So estimate the overhead cost as 50M
>  for aarch64 and 20M for other architectures based on the following
>  empirical data,
>  
>  | Overhead (M) | OS                                        | arch    |
>  | ------------ | ----------------------------------------- | ------- |
>  | 14.1         | RHEL-9.2.0-20220829.d.1                   | ppc64le |
>  | 14           | Fedora-37-20220830.n.0 Everything ppc64le | ppc64le |
>  | 17           | Fedora 36                                 | ppc64le |
>  | 8.8          | Fedora 35                                 | s390x   |
>  | 10.1         | Fedora-Rawhide-20220829.n.0, fc38         | s390x   |
>  | 42           | Fedora-Rawhide-20220829.n.0, fc38         | arch64  |
>  | 40           | F35                                       | arch64  |
>  | 42           | F36                                       | arch64  |
>  | 42           | Fedora-Rawhide-20220901.n.0               | arch64  |
>  | 10           | F35                                       | x86_64  |
>  | 10           | Fedora-Rawhide-20220901.n.0               | x86_64  |
>  | 11           | Fedora-Rawhide-20220901.n.0               | x86_64  | 
this approach isn't very elegant but looks like it's the best we can
do. At least it's better than before ;-)

Reviewed-by: Philipp Rudo <prudo(a)redhat.com&gt;

P.S. do_estimate is slowly getting pretty long and hard to read. Maybe
it's worth to split it up next time we work on it.

>  
>  [1] https://lore.kernel.org/cryptsetup/20220616044339.376qlipk5h2omhx2@Rk/T/#u
>  
>  Fixes: e9e6a2c ("kdumpctl: Add kdumpctl estimate")
>  Signed-off-by: Coiby Xu <coxu(a)redhat.com&gt;
>  ---
>   kdumpctl | 14 ++++++++++++--
>   1 file changed, 12 insertions(+), 2 deletions(-)
>  
>  diff --git a/kdumpctl b/kdumpctl
>  index ee40d33..18abdd7 100755
>  --- a/kdumpctl
>  +++ b/kdumpctl
>  @@ -1192,7 +1192,7 @@ do_estimate()
>   	local kdump_mods
>   	local -A large_mods
>   	local baseline
>  -	local kernel_size mod_size initrd_size baseline_size runtime_size reserved_size
> estimated_size recommended_size
>  +	local kernel_size mod_size initrd_size baseline_size runtime_size reserved_size
> estimated_size recommended_size _cryptsetup_overhead
>   	local size_mb=$((1024 * 1024))
>   
>   	setup_initrd
>  @@ -1246,7 +1246,17 @@ do_estimate()
>   			break
>   		done
>   	done
>  -	[[ $crypt_size -ne 0 ]] && echo -e "Encrypted kdump target requires extra
> memory, assuming using the keyslot with minimun memory requirement\n"
>  +
>  +	if [[ $crypt_size -ne 0 ]]; then
>  +		if [[ $(uname -m) == aarch64 ]]; then
>  +			_cryptsetup_overhead=50
>  +		else
>  +			_cryptsetup_overhead=20
>  +		fi
>  +
>  +		crypt_size=$((crypt_size + _cryptsetup_overhead * size_mb))
>  +		echo -e "Encrypted kdump target requires extra memory, assuming using the keyslot
> with minimun memory requirement\n"
>  +	fi
>   
>   	estimated_size=$((kernel_size + mod_size + initrd_size + runtime_size + crypt_size))
>   	if [[ $baseline_size -gt $estimated_size ]]; then