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Comment Re:Not new (Score 1) 41

No, they are not doing this for publicity. Their goal is to improve the review process by attracting more people interested in the topic to the review process and make it more open.

I happened to attend the workshop last year and there was a very interesting discussion at the end about how to modify a review process to make it more open. While I didn't take part in the discussion, there were many aspects considered about the open peer-review process, both positive and negative. For example, some authors might be frightened to submit a paper when sending preliminary versions of their work. The selection of Reddit and ArXiv didn't have any publicity (or political) objective, they were just tools familiar to the people involved in the organization and the discussion.

I am some skeptical to this model, but still is a very interesting experiment so it will be nice to see how it compares to the reviews from previous editions.

Comment Re:tl;dr; (Score 1) 102

Of course the title is misleading! For a user-space programmer, the ISA is completely hidden by the compiler and the system libraries (for example, synchronization). Still, the document makes interesting points, such as different behaviour of the compiler (which apparently removes locks in ARM32 but not in ARM64) which could impact performance, especially for highly concurrent applications.

Comment Re:Double every 4 years and it will take less than (Score 1) 269

You forget the simple fact that no exponential growth can be sustained forerver. Moore's law will come to an end (in a few years, btw), simply when the required size for transistors is smaller than a single atom (or a single sub-atomic particle if we manage to do that; the idea is the same). Dennard's scaling has already hit the wall. Networking will never send data using less than a single photon per bit (actually, the limit imposed by quantum noise is around 15-20 photons/bit) or a single electron/bit, and the amount of them is limited by transmission power. So no, there are some achievements which we won't obtain, because of simple phisical limits. You cannot simply sit and wait.

Comment Spanish SEAT too; CEO climbing in the group... (Score 1) 494

The Spanish brand SEAT, part of VW group, used some 500.000 of these tampered engines. Jürgen Stackmann, the CEO of SEAT is also leaving this company.

However, apparently he is not being fired, instead he will become the group worldwide sales chief (link in German).

Interesting and sad to see how some people are being blamed and fired, while others (in the same position in other company of the group) manage to leave unpunished and even use this opportunity to climb in the group.

Comment Networking blog: (Score 1) 203

I follow Ivan Pepelnjak at for advanced networking stuff (some topics are CCIE-level). He is great at explaining concepts, has strong opinions on new technologies and provides links to background information. He also gives weminars on multiple technologies (most are paid). Great source of information to get in touch with reality, apart from what appears in networking books. (Disc: I am not affiliated with him, but follow the blog and have attended some paid weminars).

Comment Service level (Score 1) 170

It's not just bandwidth, it's also discard priority according to the service class of each customer.

In case of congestion, you'd better belong to the "gold" class (highest paying customers) rather than the "silver" or "bronze" classes. I don't actually know the number of classes nor their names as defined internally by Verizon, but customers are typically classified in several classes, and their traffic is treated differently. Maximum bandwidth is the first (obvious) difference, but not the only one. In general traffic from higher classes is typically forwarded faster in the routers (i.e., it employs higher-priority queues in the routers, suffering less delay and jitter due to congestion) and in case of congestion, packets from lower classes are typically discarded first.

It is obvious that 50 Mbps is far more than enough bandwidth for Netflix, but in any case there is a small difference between the available service levels (which, by the way, the rep from Verizon probably didn't even know).

Comment Distributed notification (Score 1) 159

So... I add a Canary to my site, and when I remove it, you launch an announcement in yours. Aren't we building together a distributed system which violates the explicit compulsory silence associated to the order? I mean, a canary is used because an explicit announcement is forbidden, so this system might constitute an explicit violation of the silence order, without the original user (the one who added the canary) even knowing. Is this correct? Are both parties liable?

Comment Original sources (Score 2) 161

It is really surprising that neither the linked Extremetech article, nor the slashdot summary cite the original source. This research was presented in HPCA'13 in a paper titled "Power Struggles: Revisiting the RISC vs. CISC Debate on Contemporary ARM and x86 Architectures", by Emily Blem et al, from the University of Wisconsin's Vertical Research group, led by Dr. Karu Sankaralingam. You can find the original conference paper in their website.

The Extremtech article indicates that there are new results with some additional architectures (MIPS Loongson and AMD processors were not included in the original HPCA paper), so I assume that they have published an extended journal version of this work, which is not yet listed in their website. Please add a comment if you have a link to the new work.

I do not have any relation with them, but I knew the original HPCA work.

Comment Problem and possible alternatives (Score 5, Informative) 131

This is a real pity for the TM community. This is not the first chip with transactional memory support in hardware: The Sun Rock was announced to have hardware TM support, and the IBM Blue Gene/Q Compute chip also supports it. Unlike other proposals for unbounded transactional memory, all these systems employ Hybrid Transactional Memory (ref, ref, ref), in which restricted hardware transactions are designed to correctly coexist with unbounded software transactions, so a software transaction can be started in case a hardware transaction fails for some unavoidable issue (such as lack of cache size or associativity to hold speculative data from the transaction, not because of a conflict). Note that, in any case, very large transactions should arguably be very uncommon, since they would significantly reduce performance (similar to very large critical sections protected by locks).

The problem with the hardware implementation of transactional memory is that they are not simply a new set of instructions which are independent from the rest of the processor. HTM implies multiple aspects, including multiversioning caching for speculative data; allowing for the commit of speculative (transactional) instructions, which could be later rolled back (note that in any other speculative operation such as instructions after branch prediction, the speculation is always resolved before instruction commits because the branch commits earlier); a tight integration with the coherence protocol (see LogTM-SE for an alternative to this very last issue, but still...); a mechanism to support atomic commits in presence of coherence invalidations... From the point of view of processor verification, this is a complete nightmare because these new "extensions" basically impact the complete processor pipeline and coherence protocol, and verifying that every single instruction and data structure behaves as expected in isolation does not guarantee that they will operate correctly in presence of multiple transactions (and non-transactional conflicting code) in multiple cores. There are some formal studies such as this or this, and the IBM people discuss the verification of their Blue Gene TM system in this paper (paywalled).

As some others commented before, the nature of the "bug" has not been disclosed. However, since it seems to be easy to reproduce systematically, I would expect it to be related to incorrect speculative data handling in a single transaction (or something similar), rather than races between multiple transactions.

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.

Comment They are right - Uses of unicode ambiguous letters (Score 1) 79

They are right doing so. There are letters in different alphabets whose typing is very very similar -- or in fact they are written exactly the same, depending on the font used.

This can be exploited for interesting uses. For example, "E" and "ÃZ"** are respectively the latin "e" and the greek "epsilon" vowels, but they are indistinguishable in caps, at least in Arial font. The second one is the UTF 395 code. My name has an "E" on it, and for my email signature I spell my name using the traditional latin letter from the keyboard when the email is important and should be archived. By contrast, when the email is mostly irrelevant for future use (such as meeting arrangement emails, which are useless after the meeting takes place) I spell my name using the Greek epsilon letter (hint: 395 followed by Alt+X in most Windows programs). There is no obvious difference for the receiver, but a search tool can be used to quickly find all sent emails which can be deleted safely.

While the previous is a somehow "legit" use, in general any word which combines letters from different alphabets could be used to confuse an trick the receiver, for example by creating an email account which reads exactly the same as the one from another person. There is a nice image of 5 letters a-b-c-d-e in different alphabets in the linked post. I agree with Google in preventing such combinations for email accounts. It would be interesting to know the exact policy used to forbid account names, which is not detailed.

** At the time of writing, these two letters look exactly the same. Classic Slashdot lacks Unicode support and does not represent the greek Unicode letter from my comment. I tried logging into Slashdot Beta (first time, I swear it!!) and it seems to represent a different letter... Please try this on your own computer!

I have a theory that it's impossible to prove anything, but I can't prove it.