Dear Ard, On 03/25/18 17:21, Paul Menzel wrote: > On 03/25/2018 09:41 AM, Paul Menzel wrote: > >> On 03/24/2018 11:35 PM, Ard Biesheuvel wrote: >> >>> On 24 March 2018 at 22:10, Paul Menzel wrote: > >>>> 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? >>> >>> That depends. These are firmware calls, so to make these calls faster, >>> you need to modify the firmware, not the kernel. >> >> Yeah, unfortunately, no free firmware runs on this laptop, and Dell doesn’t respond to these kind of reports, as they think, it’s not important. >> >>> We may be able to make more intrusive changes to get rid of this >>> delay, e.g., spin up a special kernel thread, but I'd have to check in >>> more detail. >> >> That’d be great. On the MSI B350M MORTAR (MS-7A37) it takes even longer, almost 50 ms. ``` [ 0.204009] calling efisubsys_init+0x0/0x30a @ 1 [ 0.204009] Registered efivars operations [ 0.252262] initcall efisubsys_init+0x0/0x30a returned 0 after 46875 usecs ``` If a solution could be found to move this out of the hotpath, that’d be great. But I am not sure, if threads can be used that early. >>> In the mean time, you can try passing 'efi=noruntime' to the kernel. […] >>>> 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
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