long boot times with zram_count=16 about systemd-swap HOT 6 OPEN

From my point of view it can be closed. Thank you!
But can you share a link to the systemd PR here?

from systemd-swap.

First thing, you should always use only one zram device since there's no performance improvement from having multiple (this should be documented). Secondly I'd recommend systemd/zram-generator if you only use zram (should also be documented).

I'll keep this issue in mind, but don't expect any patches soon.

from systemd-swap.

First thing, you should always use only one zram device since there's no performance improvement from having multiple (this should be documented).

That is interesting because the default behavior is actually that it creates ${NCPU} zram devices. I just tested it by commenting the zram_count in the config file. Shouldnt the default then be just one zram device?

And it does not explain where the dependency to dbus-broker is coming from: 49 s without dbus-broker compared to 4 s with dbus-broker is a big difference.

from systemd-swap.

Please read this:
https://www.kernel.org/doc/html/latest/admin-guide/blockdev/zram.html#set-max-number-of-compression-streams

Since we have multiple streams per zram device - there is no use to have multiple zram devices.
An exception might be with multiple NUMA devices? Although - I don't know if the kernel takes this into account.

from systemd-swap.

The referenced systemd issue got resolved, bug was identified as something missed during 2016 commit. PR was merged recently for upcoming v251 release of systemd.

dbus-broker avoided the issue as it doesn't try to do some logic that dbus-daemon was doing (which IIRC was timing out from a deadlock or something like that), dbus-daemon also queues messages differently I think, so your experience with multiple devices vs single was likely related to behaviour with that?

Should be safe to close issue? (unless you want to wait for v251 release and broader availability)

from systemd-swap.

can you share a link to the systemd PR here?

systemd/systemd#22552

from systemd-swap.