On Aug 23, 2013, at 10:17 AM, Warner Losh <[email protected]> wrote:
> The relative magnitude of the bug is several times worse than the USB bug.
If this assertion is true, then it should be possible to quantify it. They
both remain Linux bugs, however.
> The side effects were kernel crashes or tight loops. The crashes were easy to
> cope with, but the tight loops caused a large spike in the power utilization
> of the data center, in some cases tripping breakers taking entire racks
> offline. The energy had to be generated somewhere... In the jargon of the IT
> industry, this is considered havoc, even if the literal, non-technical usage
> means something else.
What the Facebook Site Operations VP said adds up to something else: “The
number of cabinets brought down was not significant enough for it to impact our
users.” and:
When Furlong looked at the spike in Facebook’s data center power usage, he saw
opportunity as well as risk. […] “A lot of this plays into our efficiency
initiatives,” said Furlong, who said his team must balance the need for both
flexibility and efficiency. “Through the leap second, we found that we were
good on flexibility. One of the efficiencies we now want to drill into is how
we use the building.”
"Havoc" is hyperbole.
> People do not take the leap second standard seriously in the computer
> industry, while the USB standard is taken seriously…
It's the UTC standard, not the "leap second" standard. Leap seconds are a
means to an end. And from the USB article:
"Sharp believes that from a hardware programmer’s perspective this
TRSMRCY value is the minimum and not the maximum."
Legislating leap seconds out of existence is the equivalent of attempting to
redefine a minimum to be the maximum. Yes, they are taking it seriously - by
not attempting to redefine a minimum to be a maximum, but rather by fixing the
implementation.
> So the root cause is the same (not implementing the standard correctly), the
> effects differ by orders of magnitude in severity. Once the severity crossed
> a specific level, of course the news papers are going to engage in a bit of
> hyperbole to sell copy. But the key point here is that it wasn't just pure
> hype because people love USB and hate UTC: The effects were measurably much
> worse in one instance than in the other.
So measure them and report back. Don't forget to normalize the relative impact
to the impact of the massive mid-Atlantic storm that was happening at the same
time.
> If a driver of a car falls asleep, and then wakes up to scraping sounds as
> they peel a few layers of paint of the side of the car on a guardrail, this
> might warrant a mention in the local, small-town newspaper. If a driver falls
> alseep and plows into a parade, killing a couple and injuring dozens then
> that will be covered in a much more sensationalistic way. The root cause in
> both cases is the same (falling asleep at the wheel), but since the effects
> are much more random and severe in the second case it gets much more
> attention.
No, not hyperbole at all…
Rob
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