[LEAPSECS] How USB bugs are reported versus UTC

[Rob Seaman]

On Aug 23, 2013, at 10:17 AM, Warner Losh <imp at bsdimp.com> 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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