On 22 August 2018 at 15:18, Paul Menzel <pmenzel+linux-efi@xxxxxxxxxxxxx> wrote: > 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. > Could you narrow this down? Which call in efisubsys_init() is taking up all this time?
