Updated JavaScript interpreter to help boost WebKit’s performance by 2, 2.5x

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Date: Friday, March 2nd, 2012, 08:22
Category: iOS, News, Software

You can’t argue that WebKit’s been good for Apple and iOS in general.

Apple’s WebKit JavaScriptCore is now a “triple tier virtual machine,” offering the potential for 2-2.5 times faster JavaScript performance in Safari.

Per webkit.org, recent changes in Apple’s WebKit open source project (used by Safari on OS X and iOS, and to power a wide variety of other browsers) include the incorporation of the efficient new LLInt (Low Level Interpreter), which is now used by JavaScriptCore (JSC) to attempt executing code before passing it to the standard interpreters, either the bytecode virtual machine or the JIT (Just In Time complier) which builds native machine code on the fly.

“JSC will now will start by executing code in LLInt and will only tier up to the old JIT after the code is proven hot,” a change report on the new interpreter describes.

“LLInt is written in a modified form of our macro assembly. This new macro assembly is compiled by an offline assembler (see offlineasm), which implements many modern conveniences such as a Turing-complete CPS-based macro language and direct access to relevant C++ type information (basically offsets of fields and sizes of structs/classes).”

The new interpreter “is 2-2.5x faster than our old interpreter on SunSpider, V8, and Kraken [benchmarks],” the report states. “With triple-tiering turned on [to allow the LLInt to interpret code], we’re neutral on SunSpider, V8, and Kraken, but appear to get a double-digit improvement on real-world websites due to a huge reduction in the amount of JIT’ing.”

JavaScript performance in web browsers is a primary focus for optimization, as the faster and more efficiently code can be executed, the more fluid animations can run and the more sophisticated and responsive cross platform web applications can be.

The LLInt enhancements to JavaScriptCore appear to have been contributed by Filip Pizlo, who joined WebKit as a reviewer in December after acting as a “major contributor” to improvements to the JavaScriptCore JIT and Garbage Collector. Pizlo filed a bug report in January noting that “JSC should be a triple-tier VM,” and subsequently solved the issue by the end of February.

The new changes to JavaScriptCore will take some time to make it into the mainstream version of Safari, following similar WebKit enhancements of previous years. Enhancements in Apple’s next release of Safari 5.2 have been profiled in reports describing its new user interface and sharing enhancements and new privacy settings and website alert features.

In 2008, WebKit announced a rewriting of JavaScriptCore as a direct-dispatch register based, high-level bytecode virtual machine originally named SquirrelFish. It compiled JavaScript into native machine code. The project was later enhanced to gain the codename SquirrelFish Extreme.

Stay tuned for additional details as they become available.

Rumor: Apple may include Intel Sandy Bridge processors in near-term Mac Pro update

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Date: Friday, March 2nd, 2012, 07:27
Category: Mac Pro, Processors, Rumor

Even if you’re hankering for a new iPad 3 or an updated MacBook Air, there’s always your Mac Pro tower to keep in mind.

Per The Inquirer, Intel’s new Sandy Bridge update for its Xeon line of high end CPUs is due next week, suggesting the potential for Apple to refresh the Mac Pro, which hasn’t changed since the middle of 2010.

The new Xeon E5 chips incorporate the Sandy Bridge micro architecture that first appeared in MacBook Pros and iMacs early last year, followed by a mobile variant used by Apple in the MacBook Air last summer.

Apple’s latest Mac Pro models currently use Intel Xeon Bloomfield or Gulftown processors based on the Nehalem and closely related Westmere microarchitectures.

The latest release of OS X 10.7.3 Lion included support for AMD’s high end Tahiti graphic cards, which are expected to arrive in the market around the same time as Intel’s new Xeon chips.

However, sources famliar with the matter have said that Apple’s management, as far back as last May, were in limbo over whether to put any additional resources toward the Mac Pro product line.

Internal discussions at Apple were said to focus on the fact that sales of the high-end Mac Pro workstations have dropped off so considerably that the desktop machines are no longer particularly profitable for the company.

Stay tuned for additional details as they become available.

AT&T publishes full content of company’s data-throttling policy

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Date: Friday, March 2nd, 2012, 07:02
Category: iPhone, News

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After a fair amount of consternation, wireless provider AT&T has published a Web page laying out precisely who will be affected by the policy, and what customers’ options are.

Per Macworld, unlimited data customers on the 3G network will be warned via text message when their usage approaches 3GB within a single billing cycle. If the 3GB ceiling is breached, users will find their data speed reduced for the remainder of the billing cycle; as of the beginning of the subsequent cycle, however, their speed will return to normal. Data quantity is truly unlimited, though, the carrier says—customers can continue to use as much as they want, even after the 3GB ceiling is passed. The company does not specify by how much customers’ speeds will be reduced.

Customers using the carrier’s 4G LTE network have a higher threshold; their speeds will only be dialed down once they hit 5GB.

AT&T says that the speed reductions will only affect the top 5 percent of its customers. The measures have been put in place because of the rapid increase in wireless data traffic created by the increased adoption of smartphones in the past five years; by AT&T’s figures, that number has skyrocketed from 7 million phones in 2006 to 39.4 million in 2011, yielding a wireless data traffic increase of 20,000 percent. According to AT&T, it has invested US$95 billion in its networks over that period, including US$20 billion in 2011; another US$20 billion is earmarked for 2012.

In addition, the network lays out where the majority of that data is getting eaten up, which is to say streaming HD movies. AT&T’s handy chart estimates that streaming HD movies gobbles up 306MB an hour, a sizable increase from the roughly 120MB of data that AT&T says one hour of standard video consumes.

Users can check their current month’s data usage by dialing *data# on their mobile phone’s keypad, or access previous months’ usage at their AT&T account online. The company also offers a mobile app for iPhones that provides the same data.

As for customers’ options, AT&T lays out a few suggestions, including using Wi-Fi when available, since that data does not count against the carrier’s data plans. And, of course, customers can continue using their current unlimited data plan, if they don’t mind the speed reductions. Users can also switch to one of the company’s current tiered data plans, which offer 300MB for US$20 per month, 3GB a month for US$30, or 5GB per month for US$50. But, in those cases, users must pay overage charges for exceeding the data cap: US$20 for another 300MB on the lowest plan, US$10 per gigabyte on either of the higher plans. That would seem to give little incentive for unlimited data customers to switch.

Stay tuned for additional details as they become available.