On 5/24/23 08:44, Zdenek Kabelac wrote: > Dne 20. 05. 23 v 22:43 Demi Marie Obenour napsal(a): >> I noticed that by default, Qubes OS has voluntary kernel preemption >> as opposed to full preemption. I found that enabling full preemption >> (preempt=full on kernel command line) makes the system significantly >> more responsive under heavy I/O load. In particular, if I build a >> kernel in a Qubes OS VM, it significantly degrades responsiveness >> without preempt=full. With preempt=full, the system remains >> responsive. The storage stack used is LVM thin provisioning on LUKS, >> and I have observed significant CPU usage in dom0 kernel threads with >> names that indicate they are related to dm-thin and dm-crypt. >> >> The kernel config used by the Qubes kernel package I use (6.1.28) is >> based on Fedora 37’s config, and Marek Marczykowski-Górecki (CCd) >> indicated that the same arguments apply to Fedora. Therefore, I am >> asking if Fedora should use full kernel preemption by default. > > > Hi Demi > > > Could you please provide 'dmsetup table' - so we could see how doe your > device stack looks like ? The output of 'dmsetup table' contains all qube names so I would prefer to not post it publicly. The device stack is NVMe -> crypt -> linear -> thin pool -> thin. > Aren't you disabling work-queues on the table line for crypt targets ? The only optional parameter passed to dm_crypt is allow_discards, so presumably no. -- Sincerely, Demi Marie Obenour (she/her/hers)
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