[systemd-devel] Reducing unmount/mount of partitions on soft-reboot

[Aditya Gupta]

On 13/03/24 18:09, Luca Boccassi wrote:

> On Wed, 13 Mar 2024 at 12:30, Aditya Gupta <adityag at linux.ibm.com> wrote:
>> Hello,
>>
>> I tried systemd-soft-reboot on a RHEL system, and it's amazing in terms
>> of it's ability to do a userspace reboot, within fraction of time of a
>> full system reboot. For example, for a Power system taking around 50
>> seconds to do a normal reboot, it took around 4-5 seconds for a
>> systemd-soft-reboot.
>>
>> I have a question on further optimisation. After soft-reboot, I notice
>> much of the time is taken up by .device and .mount services. This was my
>> observation based on 'systemd-analyze blame'. Please do let me know if
>> I am seeing the wrong numbers, or if there's a better way to know.
>>
>> Is there some way to 'pass-through' these mounts ? That is, I might not
>> need to unmount and remount my boot/root paritions.
>>
>> I tried finding this in available documentation, sorry if I missed it. I
>> did find this ability to 'pass-through' resources/file
>> descriptors/sockets to next boot, by modifying the service files, but
>> don't know how and if I can do a similar thing with mounts.
> Pre-prepare the additional mounts in /run/nextroot/, after preparing
> the new rootfs, so that they are ready ahead of time.

Thanks for the idea Luca Boccassi ! Makes sense.
Guess it's supported in this way then.


Thanks,

- Aditya Gupta