Xen With Linux 5.16 Will Allow For Faster Booting Of Guests
Xen para-virtualized guests booting on the Linux 5.16 kernel should see noticeably quicker boot times.
Sent out today were the Xen patches for Linux 5.16. Besides having some code clean-ups, para-virtualized interrupt masking made simpler, Xen "pciback" driver support for Arm, and other smaller enhancements, there is also work to speed-up guest booting. In particular, the booting up of Xen PV (para-virtualized) guests should be much quicker with Linux 5.16 and beyond.
Jan Beulich of SUSE wrote in the prior patch series when first proposing the Xen PV guest boot optimizations, "The observed (by the human eye) performance difference of early boot between native and PV-on-Xen was just too large to not look into. As it turns out, gaining performance back wasn't all that difficult. While the series (re)introduces a small number of PTWR emulations on the boot path (from phys_pte_init()), there has been a much larger number of them post-boot. Hence I think if this was of concern, the post-boot instances would want eliminating first."
More details via the Xen pull request for the Linux 5.16 kernel merge window that is ending this weekend.