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Comment Re:So how does one find out /apply "fix" with linu (Score 1) 131 131

If you have a recent version of the cpuid tool, you can run:

cpuid |grep RTM

and you'll see something like:

RTM: restricted transactional memory = false
RTM: restricted transactional memory = false
RTM: restricted transactional memory = false
RTM: restricted transactional memory = false

/proc/cpuinfo doesn't show it, presumably because no kernel support is needed at all for this feature. (And that's why, if this is indeed a privilege escalation issue, it won't be easily fixed with a kernel change.)

Comment Re:Problem and possible alternatives (Score 1) 131 131

Regarding the alternatives, Intel cannot simply remove these instructions opcodes because previous code would fail. I assume that the patch will make all hardware transactions fail on startup, with an specific error (EAX bit 1 indicates if the transaction can succeed on a retry; setting this flag to 0 should trigger a software transaction). In such case, execution continues at the fallback routine indicated in the XBEGIN instruction, which should begin a software transaction. Effectively, this will be similar to a software TM (STM) with additional overheads (starting the hardware transaction and aborting it; detecting conflicts with nonexistent hardware transactions) that would make it slower than a pure STM implementation.

This seems unlikely to me. I'd expect that the patch will clear the cpuid bit for TSX and cause #UD (undefined opcode) on XBEGIN, etc.

Comment Re:Netgear R7000 (Score 1) 427 427

Buying an R7000 is a waste of money. The whole "AC1900" class is a joke -- they squeeze out the extra Mbps by supporting a nonstandard, Broadcom-only modulation in the 2.4 GHz band. Good luck finding any client devices that can use that modulation.

Stick with AC1750 and stop feeding the marketing trolls.

Comment Re:Atheros and OpenWRT (Score 1) 427 427

The TP-Link Archer C7 v2 is pretty mature. The v1 is discontinued, and most US-based vendors are now explicitly advertising v2 hardware. The only real caveat is that the open-source ath10k support is very slightly flaky -- you may have intermittent issues if you have a Macbook Pro. This will probabaly be fixed soon.

Submission + - IRS: give us machine-readable tax formulas

johndoe42 writes: Now that tax day is almost over, it's time to ask the IRS to make it less painful. All of the commercial tax software is awful, overpriced, and incompatible with everything else. Some people have tried to do better: OpenTaxSolver and a rather large Excel spreadsheet are tedious manual translations of the IRS's forms. I'm sure that many programmers would try to make much friendlier tax software if they didn't have to deal with translating all of the IRS instructions. Let's petition the IRS to publish computerized formulas so that this can happen.

Comment Re:Except for the fact that... (Score 1) 114 114

This is incorrect. You can't build a passive device that is 100% transmissive from one side and 100% reflective on the other side.

You can, however (in theory), build a device that with these properties:

  1. Light from side A is transmitted and comes out side B
  2. Light from side B is absorbed and turns into heat
  3. Absorbed heat is re-radiated, mostly from side A

This thing will be non-reciprocal. I've never heard of anyone building one that looks like a sheet of glass, but they're common for microwaves -- they're called circulators. There's a reason that this new contraption is called an acoustic circulator. The only misleading part is that one-way glass is reciprocal -- this new thing is much more impressive than one-way glass.

Comment Re:RSA sold you out (Score 1) 464 464

Here is what I personally don't get and since I'm not a crypto guy maybe I'm missing something but here looks like all these attacks come from using a RNG that has been rigged to be less than random, but why use their RNG when there are so many sources of randomness in the world?

There is the background radiation of the universe for starters, and how many webcams are freely accessible in heavily trafficked public places? It shouldn't be hard to write a program that does a quick head count, multiple that by the dollar amount of the biggest box office draw last week. How many letters is in headlines of the top 60 newspapers on the planet? Multiple that by the amount of temp detected by 30 weather stations and divide by the number of folks who went to see the fourth most popular movie yesterday squared by the ratings of the most popular reality show.

You can do things like this (with a little bit more care) to generate numbers that can't be predicted in advance. Unfortunately, that's not the point. Web servers need random numbers that can't be guessed or manipulated by anyone, and they need to generate lots of them. If everyone generated the same random numbers (because they looked at the same webcams), then those numbers aren't useful for cryptography.

Comment Re:Catastrophic (Score 1) 464 464

Except that RSA destroyed their whole business a couple of years ago when it was found that they'd left the root keys for their SecureID tokens on an unsecured, network-connected machine. After that no one could trust them again.

RSA lost my trust when I found out that root keys or critical secrets for the SecureID system existed in the first place.

If they designed the system well, they would make physical tokens and deliver the tokens and the keys for those tokens to the clients. They would not keep any record whatsoever of those keys, nor would they have a way to reconstruct them

As a physical analogy, a locksmith making safety deposit box keys should make a random key and not write down the key code

Comment That's a lot of 12V loss (Score 1) 239 239

Before the battery replacement, the car lost 3.5kWh/day. After the replacement, it lost 1.1kWh/day. That's a difference of 2.4kWh/day, which is 100W. That's something like 8 Amps internally leaking in the 12V battery. That seems shockingly high. Or maybe there's something else going on. If the battery was marginal, then perhaps the car's DC-DC converter was continually "charging" it but actually overcharging it. Then it would be electrolyzing 8A worth of water and battery acid. I expect that would make a giant mess. Alternatively, it just keeps running the DC-DC converter at very low output. The DC-DC converter could be incredibly inefficient when producing just a little bit of current (Tesla is reputed to use a huge (~200A) DC-DC converter, so the thing could be running at about 1% of rated output at, say, 10% efficiency).

Comment Re:Warm up is a big deal (Score 1) 371 371

These people should be using a real time Java VM and an ahead of time compiler for those parts.

It means you can skip the warm up. The only problem with it is you can't hire regular Java guys - real time Java is a little bit special, and you can't use regular Java collections and other things in the ways you'd expect.

That's not the only problem. Doing this switches you from using a well-standardized, well-supported language to a nonstandard subset. This removes a lot of the advantages of Java.

One of the most technically competent exchanges I work with is trying out Azul, which is (AFAIK) the top-of-the-line low-latency JVM. I was a bit surprised to learn that their software didn't Just Work. In fact, it didn't work at all. So now they have to decide which AOT-compiling JVM to run and figure out how to support it. I suppose that Excelsior and gcj (eek!) would be other options.

My main point here is that, when low latency is involved, a lot of people cite the existence of high-quality real-time JVMs as evidence that Java is a good choice. These JVMs exist, but they are by no means panaceas, and users of Java for real-time or low-latency work will need to make a real technical and monetary investment in dealing with them. Hotspot is not (yet?) appropriate for this kind of thing. Oddly, .NET seems be in better shape here, at least in terms of AOT compilation.

Comment Warm up is a big deal (Score 3, Interesting) 371 371

I'm not a Java user, so I've never directly tuned for things like GC, nor do I interact with it directly. Warm up is a different story.

I interact with quite a few exchanges (over all kinds of protocols). Most are, unsurprisingly, written in Java. Almost all of them perform terribly at the beginning of the week. The issue is a standard one: the JVM hasn't JITted important code paths, and it won't until several thousand requests come in. For a standard throughput-oriented program, this doesn't matter -- the total time wasted running interpreted code is small. For a low-latency network service, it's a different story entirely: all of this wasted time happens exactly when it matters.

The standard fix seems to be to write apps to exercise their own critical paths at startup. This is *hard* when dealing with front-end code on the edge of the system you control. Even when it's easy, it's still something you have to do in Java that is entirely irrelevant in compiled languages.

If JVMs some day allow you to export a profile of what code is hot and re-import it at startup, this problem may be solved. Until then, low-latency programmers should weigh the faster development time of Java with the time spent trying to solve annoying problems like warm-up.

The most difficult thing in the world is to know how to do a thing and to watch someone else doing it wrong, without commenting. -- T.H. White