intel efi system too slow

intel efi system too slow

[Giorgio Dal Molin]

Hi,

I'm working on an embedded system with an intel CPU (atom).

I've built a barebox from the current master (v2017.10.0) and it
runs and can actually boot a kernel.

Nevertheless I think the bootloader is very slow, for example when
reading or writing files to the disk (an industrial CFastCard). 

After the kernel starts the system becomes fast 'es expected'.

While barebox starts up I noticed the following line on the console:

...
EFI Event timer too slow freq = 50 Hz
...

I found the warning in the source file 'drivers/clocksource/efi.c':

static int efi_cs_init(struct clocksource *cs)
{
	efi_status_t efiret;
	uint64_t freq;
...
	freq = 1000 * 1000;
	if (ticks_freq() < 800 * 1000) {
		uint64_t nb_100ns;

		freq = ticks_freq_x86();
		if (freq == 0) {
			BS->close_event(efi_cs_evt);
			return -ENODEV;
		}
		nb_100ns = 10 * 1000 * 1000 / freq;
		pr_warn("EFI Event timer too slow freq = %llu Hz\n", freq);
		efiret = BS->set_timer(efi_cs_evt, EFI_TIMER_PERIODIC, nb_100ns);
		if (EFI_ERROR(efiret)) {
			BS->close_event(efi_cs_evt);
			return -efi_errno(efiret);
		}
	}
...
}

Can this be a possible reason for a too slow system or is it 'OK'
to see this warning.

I don't really know where I should start searching for a possible
problem or system misconfiguration.

giorgio

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Re: intel efi system too slow

[Sascha Hauer]

Hi Giorgio,

On Wed, Oct 18, 2017 at 12:13:16PM +0200, Giorgio Dal Molin wrote:
> Hi,
> 
> I'm working on an embedded system with an intel CPU (atom).
> 
> I've built a barebox from the current master (v2017.10.0) and it
> runs and can actually boot a kernel.
> 
> Nevertheless I think the bootloader is very slow, for example when
> reading or writing files to the disk (an industrial CFastCard). 
> 
> After the kernel starts the system becomes fast 'es expected'.
> 
> While barebox starts up I noticed the following line on the console:
> 
> ...
> EFI Event timer too slow freq = 50 Hz
> ...
> 
> I found the warning in the source file 'drivers/clocksource/efi.c':
> 
> static int efi_cs_init(struct clocksource *cs)
> {
> 	efi_status_t efiret;
> 	uint64_t freq;
> ...
> 	freq = 1000 * 1000;
> 	if (ticks_freq() < 800 * 1000) {
> 		uint64_t nb_100ns;
> 
> 		freq = ticks_freq_x86();
> 		if (freq == 0) {
> 			BS->close_event(efi_cs_evt);
> 			return -ENODEV;
> 		}
> 		nb_100ns = 10 * 1000 * 1000 / freq;
> 		pr_warn("EFI Event timer too slow freq = %llu Hz\n", freq);
> 		efiret = BS->set_timer(efi_cs_evt, EFI_TIMER_PERIODIC, nb_100ns);
> 		if (EFI_ERROR(efiret)) {
> 			BS->close_event(efi_cs_evt);
> 			return -efi_errno(efiret);
> 		}
> 	}
> ...
> }
> 
> Can this be a possible reason for a too slow system or is it 'OK'
> to see this warning.

Yes, this can be a reason why the system feels slow. a timer frequency
of 50Hz means that the smallest delay barebox can do is 1/50s. This
means that even a udelay(1) will take 20ms.
Try disabling CLOCKSOURCE_EFI (which should be the default in
efi_defconfig). barebox should than use the X86 TSC as clocksource
instead.

Sascha

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