[svlug] Inits

Alison Chaiken alison at she-devel.com
Sat Jan 17 17:38:29 PST 2015


>
> Steve Litt wrote:
> > You have me at a disadvantage because I don't think I've ever seen a
> > system boot indeterminately, or at least not in the last 10 years.


Rick writes:
> Anyway, truth to tell, I'm likewise at a disadvantage in attempting to
> intelligently discuss this problem, being both late to the party and
having
> through either luck or careful avoidance of problem scenarios not seen the
> referenced problems.

Steve and Rick, if you look in your dmesg log, you'll find that the order
of devices coming up at boot under the control of the kernel is quite
asynchronous.    Kernel developers have a limited ability to sequence
operations.   If one device driver doesn't call the methods of another, or
take a reference on the other, they may come up in any old order.   Linux
has been becoming increasing asynchronous, preemptible and unpredictable
with each passing kernel.   The advent of systemd is a sign that the trends
in the kernel are being made visible to userspace.

Akk writes:

> Things may have changed -- this is based on problems I used to hit
> five or so years ago -- but here are two cases that used to cause
> indeterminacy:
>

What really causes indeterminacy?   Hardware.   If only that pesky hardware
with its variable response times would go away, we wouldn't have all these
problems.

Why is the Linux kernel becoming so asynchronous?   Because its power
management and speed used to stink compared to Windows and iOS on the same
hardware.   Don't take my word for it; look at these Intel slides from 2010:

https://events.linuxfoundation.org/slides/2010/linuxcon2010_brown.pdf

Len Brown is a Linux developer employed by Intel.   I see no reason to
think that his numbers are not valid.

That was 2010.   If Linux's power management were still that bad, Android
phones would trail iOS and Windows Phone handsets by so far in battery
lifetime that Android would not be viable.    Yes, I know that Android
phones run almost exclusively on ARM processors.   The true beauty of open
source is that Intel's quite considerable efforts on power management on
big iron in data centers helps rival processors in the embedded space as
well.

The operating system market remains highly competitive.   I believe that
Linux may be *losing* market share to QNX in automotive, where I work, for
example.   Lightweight RTOS like Xen-based OpenMirage may give Linux a run
for its money not only in the cloud but on devices as well.   iOS is ever
more profitable.   Nowhere does desktop Linux factor into any business's
development plans, because desktop Linux generates little revenue and less
profit.

Best wishes,
Alison, returning to lurking

-- 
Alison Chaiken                           alison at she-devel.com
650-279-5600                            http://{she-devel.com,
exerciseforthereader.org}
Never underestimate the cleverness of advertisers, or mischief makers, or
criminals.  -- Don Norman
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