Dear Ard,
According to `initcall_debug`, `efisubsys_init` takes more than a few milliseconds to execute on a Dell XPS 13 9370 (Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz).
``` […] [ 0.144474] calling efisubsys_init+0x0/0x2cf @ 1 [ 0.144474] Registered efivars operations [ 0.173690] initcall efisubsys_init+0x0/0x2cf returned 0 after 27343 usecs […] ```
To get a vanilla Linux kernel to boot in well under one second, it’d be nice if the time could be improved. Do you know, why it takes so long?
According to `bootgraph.py` from pm-graph [1][2] it takes even a little longer.
efisubsys_init: start=690.841, end=720.493, length(w/o overhead)=31.250 ms, return=0
There are several dozen calls to `virt_efi_get_next_variable()` all but one taking around 0.335 ms. This path needs to be optimized. Is that possible?
To reproduce this, clone the pm-graph repository [2], use `sudo ./bootgraph.py -f -fstat -maxdepth 10 -manual` to see what to add to `/boot/grub/grub.cfg`. Then reboot, and execute `sudo ./bootgraph.py -f -fstat -maxdepth 10`.
If your system is powerful enough, you can use a higher maximum depth. I didn’t get around how `-cgfilter` works to get smaller HTML files.
Kind regards, Paul [1] https://01.org/suspendresume [2] https://github.com/01org/pm-graph
