Re: Bug#734093: debian-installer: install plymouth by default
Hi Josh,
On 21.01.2014 03:35, Josh Triplett wrote:
> If splash were a non-default boot option, and plymouth did nothing
> unless the kernel command line had that option, that seems entirely
> reasonable. Very easily done; just add this to the plymouth service,
> for instance:
> ConditionKernelCommandLine=splash
I'm not sure what you are trying to say here, but you're actually
quoting line 7 of plymouth-start.service. ;)
> On current systems, there's an even better way to do that: make sure
> the kernel doesn't change the video mode set by the BIOS, and doesn't
> draw on the screen at all until X takes over. Then, you go straight
> from the BIOS or bootloader to your display manager login prompt.
> The display manager can even crossfade from the former to the latter,
> if you like.
This sounds very nice, but what happens if the boot hangs and you want
to look at the boot messages? And how would you enter a password for an
encrypted partition?
> When you're attempting to boot in a fraction of a second, 86ms is an
> eternity. If your boot process takes long enough that 86ms is lost in
> the noise, it's taking *far* too long.
It looks as if I didn't make myself clear enough. Plymouth does *not*
make the boot 86ms slower.
Looking a bit closer at my startup:
plymouth-start.service is executed in parallel to
systemd-fsck-root.service and finishes a lot before that.
plymouth-read-write.service is executed, while network.service blocks
the boot.
plymouth-quit.service and plymouth-quit-wait.service are executed in
parallel, while network-manager.service blocks the boot.
So it *seems* that plymouth makes the boot slower by 0ms!
> Furthermore, I don't think that counts the delay incurred by any mode
> switches caused by Plymouth, and to the best of my knowledge only the
> most modern systems and hardware can avoid those mode switches, so
> you're actually incurring disproportionately more of a delay on
> lower-end systems.
For these reasons I wanted to compare the whole boot time with/without
plymouth, but unfortunately for me any difference vanishes in the noise.
If you don't have such varying boot times, it would help if you could
carry out this measurement.
> On Mon, Jan 20, 2014 at 11:12:21PM +0100, Andreas Cadhalpun wrote:
>> Of course, this would be the best solution. So as soon as Debian
>> boots even on old grandma's computer in less then a second, plymouth
>> will be unnecessary. ;)
>> Unfortunately, this seems rather like utopia.
>
> It's spelled "systemd". ;)
> But seriously, that's very much the goal. And I think "less than a
> second" is not required to make a splash screen unnecessary; less than
> 5 seconds seems quite sufficient to make a splash screen superfluous.
> Plymouth and other splash screens were created when the norm was for a
> system running a desktop environment to take 30-60 seconds to boot; on
> such systems, a splash screen and progress bar seems quite reasonable.
Of course, systemd makes the boot much faster, but systemd cannot do
magic, or can it...
* ...boot in less than 5 seconds, if the kernel takes longer than 10
seconds?
* ...boot in less than 5 seconds, if a particular service takes longer
than 10 seconds (e.g. clamav-daemon)?
And the splash screen still is a nicer way to enter a password for an
encrypted partition than just a black console.
Best regards,
Andreas
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