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Original author: 
Todd Hoff

The paper MegaPipe: A New Programming Interface for Scalable Network I/O (video, slides) hits the common theme that if you want to go faster you need a better car design, not just a better driver. So that's why the authors started with a clean-slate and designed a network API from the ground up with support for concurrent I/O, a requirement for achieving high performance while scaling to large numbers of connections per thread, multiple cores, etc.  What they created is MegaPipe, "a new network programming API for message-oriented workloads to avoid the performance issues of BSD Socket API."

The result: MegaPipe outperforms baseline Linux between 29% (for long connections) and 582% (for short connections). MegaPipe improves the performance of a modified version of memcached between 15% and 320%. For a workload based on real-world HTTP traces, MegaPipe boosts the throughput of nginx by 75%.

What's this most excellent and interesting paper about?

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Todd Hoff

"It’s all a numbers game – the dirty little secret of scalable systems"

Martin Thompson is a High Performance Computing Specialist with a real mission to teach programmers how to understand the innards of modern computing systems. He has many talks and classes (listed below) on caches, buffers, memory controllers, processor architectures, cache lines, etc.

His thought is programmers do not put a proper value on understanding how the underpinnings of our systems work. We gravitate to the shiny and trendy. His approach is not to teach people specific programming strategies, but to teach programmers to fish so they can feed themselves. Without a real understanding strategies are easy to apply wrongly.  It's strange how programmers will put a lot of effort into understanding complicated frameworks like Hibernate, but little effort into understanding the underlying hardware on which their programs run.

A major tenant of Martin's approach is to "lead by experimental observation rather than what folks just blindly say," so it's no surprise he chose a MythBuster's theme in his talk Mythbusting Modern Hardware to Gain "Mechanical Sympathy." Mechanical Sympathy is term coined by Jackie Stewart, the race car driver, to say you get the best out of a racing car when you have a good understanding of how a car works. A driver must work in harmony with the machine to get the most of out of it. Martin extends this notion to say we need to know how the hardware works to get the most out of our computers. And he thinks normal developers can understand the hardware they are using. If you can understand Hibernate, you can understand just about anything.

The structure of the talk is to take a few commonly held myths and go all MythBusters on them by seeing if they are really true. Along the way there's incredible detail on how different systems work, far too much detail to gloss here, but it's an absolute fascinating talk. Martin really knows what he is talking about and he is a good teacher as well.

The most surprising part of the talk is the counter intuitive idea that many of the devices we think of as random access, like RAM, HDDs, and SSDs, effectively become serial devices in certain circumstances. A disk, for example, is really just a big tape that's fast. It's not true random access. Keep on reading to see why that is...

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Original author: 
Addy Osmani

  

Today we’ll discuss how to improve the paint performance of your websites and Web apps. This is an area that we Web developers have only recently started looking at more closely, and it’s important because it could have an impact on your user engagement and user experience.

Frame Rate Applies To The Web, Too

Frame rate is the rate at which a device produces consecutive images to the screen. A low frames per second (FPS) means that individual frames can be made out by the eye. A high FPS gives users a more responsive feel. You’re probably used to this concept from the world of gaming, but it applies to the Web, too.

Long image decoding, unnecessary image resizing, heavy animation and data processing can all lead to dropped frames, which reduces the frame rate, resulting in janky pages. We’ll explain what exactly we mean by “jank” shortly.

Why Care About Frame Rate?

Smooth, high frame rates drive user engagement and can affect how much users interact with your website or app.

At EdgeConf earlier this year, Facebook confirmed this when it mentioned that in an A/B test, it slowed down scrolling from 60 FPS to 30 FPS, causing engagement to collapse. That said, if you can’t do high frame rates and 60 FPS is out of reach, then you’d at least want something smooth. If you’re doing your own animation, this is one benefit of using requestAnimationFrame: the browser can dynamically adjust to keep the frame rate normal.

In cases where you’re concerned about scrolling, the browser can manage the frame rate for you. But if you introduce a large amount of jank, then it won’t be able to do as good a job. So, try to avoid big hitches, such as long paints, long JavaScript execution times, long anything.

Don’t Guess It, Test It!

Before getting started, we need to step back and look at our approach. We all want our websites and apps to run more quickly. In fact, we’re arguably paid to write code that runs not only correctly, but quickly. As busy developers with deadlines, we find it very easy to rely on snippets of advice that we’ve read or heard. Problems arise when we do that, though, because the internals of browsers change very rapidly, and something that’s slow today could be quick tomorrow.

Another point to remember is that your app or website is unique, and, therefore, the performance issues you face will depend heavily on what you’re building. Optimizing a game is a very different beast to optimizing an app that users will have open for 200+ hours. If it’s a game, then you’ll likely need to focus your attention on the main loop and heavily optimize the chunk of code that is going to run every frame. With a DOM-heavy application, the memory usage might be the biggest performance bottleneck.

Your best option is to learn how to measure your application and understand what the code is doing. That way, when browsers change, you will still be clear about what matters to you and your team and will be able to make informed decisions. So, no matter what, don’t guess it, test it!

We’re going to discuss how to measure frame rate and paint performance shortly, so hold onto your seats!

Note: Some of the tools mentioned in this article require Chrome Canary, with the “Developer Tools experiments” enabled in about:flags. (We — Addy Osmani and Paul Lewis — are engineers on the Developer Relations team at Chrome.)

Case Study: Pinterest

The other day we were on Pinterest, trying to find some ponies to add to our pony board (Addy loves ponies!). So, we went over to the Pinterest feed and started scrolling through, looking for some ponies to add.

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Addy adding some ponies to his Pinterest board, as one does. Larger view.

Jank Affects User Experience

The first thing we noticed as we scrolled was that scrolling on this page doesn’t perform very well — scrolling up and down takes effort, and the experience just feels sluggish. When they come up against this, users get frustrated, which means they’re more likely to leave. Of course, this is the last thing we want them to do!

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Pinterest showing a performance bottleneck when a user scrolls. Larger view.

This break in consistent frame rate is something the Chrome team calls “jank,” and we’re not sure what’s causing it here. You can actually notice some of the frames being drawn as we scroll. But let’s visualize it! We’re going to open up Frames mode and show what slow looks like there in just a moment.

Note: What we’re really looking for is a consistently high FPS, ideally matching the refresh rate of the screen. In many cases, this will be 60 FPS, but it’s not guaranteed, so check the devices you’re targeting.

Now, as JavaScript developers, our first instinct is to suspect a memory leak as being the cause. Perhaps some objects are being held around after a round of garbage collection. The reality, however, is that very often these days JavaScript is not a bottleneck. Our major performance problems come down to slow painting and rendering times. The DOM needs to be turned into pixels on the screen, and a lot of paint work when the user scrolls could result in a lot of slowing down.

Note: HTML5 Rocks specifically discusses some of the causes of slow scrolling. If you think you’re running into this problem, it’s worth a read.

Measuring Paint Performance

Frame Rate

We suspect that something on this page is affecting the frame rate. So, let’s go open up Chrome’s Developer Tools and head to the “Timeline” and “Frames” mode to record a new session. We’ll click the record button and start scrolling the page the way a normal user would. Now, to simulate a few minutes of usage, we’re going to scroll just a little faster.

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Using Chrome’s Developer Tools to profile scrolling interactions. Larger view.

Up, down, up, down. What you’ll notice now in the summary view up at the top is a lot of purple and green, corresponding to painting and rendering times. Let’s stop recording for now. As we flip through these various frames, we see some pretty hefty “Recalculate Styles” and a lot of “Layout.”

If you look at the legend to the very right, you’ll see that we’ve actually blown our budget of 60 FPS, and we’re not even hitting 30 FPS either in many cases. It’s just performing quite poorly. Now, each of these bars in the summary view correspond to one frame — i.e. all of the work that Chrome has to do in order to be able to draw an app to the screen.

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Chrome’s Developer Tools showing a long paint time. Larger view.

Frame Budget

If you’re targeting 60 FPS, which is generally the optimal number of frames to target these days, then to match the refresh rate of the devices we commonly use, you’ll have a 16.7-millisecond budget in which to complete everything — JavaScript, layout, image decoding and resizing, painting, compositing — everything.

Note: A constant frame rate is our ideal here. If you can’t hit 60 FPS for whatever reason, then you’re likely better off targeting 30 FPS, rather than allowing a variable frame rate between 30 and 60 FPS. In practice, this can be challenging to code because when the JavaScript finishes executing, all of the layout, paint and compositing work still has to be done, and predicting that ahead of time is very difficult. In any case, whatever your frame rate, ensure that it is consistent and doesn’t fluctuate (which would appear as stuttering).

If you’re aiming for low-end devices, such as mobile phones, then that frame budget of 16 milliseconds is really more like 8 to 10 milliseconds. This could be true on desktop as well, where your frame budget might be lowered as a result of miscellaneous browser processes. If you blow this budget, you will miss frames and see jank on the page. So, you likely have somewhere nearer 8 to 10 milliseconds, but be sure to test the devices you’re supporting to get a realistic idea of your budget.

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An extremely costly layout operation of over 500 milliseconds. Larger view.

Note: We’ve also got an article on how to use the Chrome Developer Tools to find and fix rendering performance issues that focuses more on the timeline.

Going back to scrolling, we have a sneaking suspicion that a number of unnecessary repaints are occurring on this page with onscroll.

One common mistake is to stuff just way too much JavaScript into the onscroll handlers of a page — making it difficult to meet the frame budget at all. Aligning the work to the rendering pipeline (for example, by placing it in requestAnimationFrame) gives you a little more headroom, but you still have only those few milliseconds in which to get everything done.

The best thing you can do is just capture values such as scrollTop in your scroll handlers, and then use the most recent value inside a requestAnimationFrame callback.

Paint Rectangles

Let’s go back to Developer Tools → Settings and enable “Show paint rectangles.” This visualizes the areas of the screen that are being painted with a nice red highlight. Now look at what happens as we scroll through Pinterest.

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Enabling Chrome Developer Tools’ “Paint Rectangles” feature. Larger view.

Every few milliseconds, we experience a big bright flash of red across the entire screen. There seems to be a paint of the whole screen every time we scroll, which is potentially very expensive. What we want to see is the browser just painting what is new to the page — so, typically just the bottom or top of the page as it gets scrolled into view. The cause of this issue seems to be the little “scroll to top” button in the lower-right corner. As the user scrolls, the fixed header at the top needs to be repainted, but so does the button. The way that Chrome deals with this is to create a union of the two areas that need to be repainted.

Screen Shot 2013-05-15 at 19.00.12-500
Chrome shows freshly painted areas with a red box. Larger view.

In this case, there is a rectangle from the top left to top right, but not very tall, plus a rectangle in the lower-right corner. This leaves us with a rectangle from the top left to bottom right, which is essentially the whole screen! If you inspect the button element in Developer Tools and either hide it (using the H key) or delete it and then scroll again, you will see that only the header area is repainted. The way to solve this particular problem is to move the scroll button to its own layer so that it doesn’t get unioned with the header. This essentially isolates the button so that it can be composited on top of the rest of the page. But we’ll talk about layers and compositing in more detail in a little bit.

The next thing we notice has to do with hovering. When we hover over a pin, Pinterest paints an action bar containing “Repin, comment and like” buttons — let’s call this the action bar. When we hover over a single pin, it paints not just the bar but also the elements underlying it. Painting should happen only on those elements that you expect to change visually.

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A cause for concern: full-screen flashes of red indicate a lot of painting. Larger view.

There’s another interesting thing about scrolling here. Let’s keep our cursor hovered over this pin and start scrolling the page again.

Every time we scroll through a new row of images, this action bar gets painted on yet another pin, even though we don’t mean to hover over it. This comes down more to UX than anything else, but scrolling performance in this case might be more important than the hover effect during scrolling. Hovering amplifies jank during scrolling because the browser essentially pauses to go off and paint the effect (the same is true when we roll out of the element!). One option here is to use a setTimeout with a delay to ensure that the bar is painted only when the user really intends to use it, an approach we covered in “Avoiding Unnecessary Paints.” A more aggressive approach would be to measure the mouseenter or the mouse’s trajectory before enabling hover behaviors. While this measure might seem rather extreme, remember that we are trying to avoid unnecessary paints at all costs, especially when the user is scrolling.

Overall Paint Cost

We now have a really great workflow for looking at the overall cost of painting on a page; go back into Developer Tools and “Enable continuous page repainting.” This feature will constantly paint to your screen so that you can find out what elements have costly paint times. You’ll get this really nice black box in the top corner that summarizes paint times, with the minimum and maximum also displayed.

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Chrome’s “Continuous Page Repainting” mode helps you to assess the overall cost of a page. Larger view.

Let’s head back to the “Elements” panel. Here, we can select a node and just use the keyboard to walk the DOM tree. If we suspect that an element has an expensive paint, we can use the H shortcut key (something recently added to Chrome) to toggle visibility on that element. Using the continuous paint box, we can instantly see whether this has a positive effect on our pages’ paint times. We should expect it to in many cases, because if we hide an element, we should expect a corresponding reduction in paint times. But by doing this, we might see one element that is especially expensive, which would bear further scrutiny!

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The “Continuous Page Repainting” chart showing the time taken to paint the page.

For Pinterest’s website, we can do it to the categories bar or to the header, and, as you’d expect, because we don’t have to paint these elements at all, we see a drop in the time it takes to paint to the screen. If we want even more detailed insight, we can go right back to the timeline and record a new session to measure the impact. Isn’t that great? Now, while this workflow should work great for most pages, there might be times when it isn’t as useful. In Pinterest’s case, the pins are actually quite deeply nested in the page, making it hard for us to measure paint times in this workflow.

Luckily, we can still get some good mileage by selecting an element (such as a pin here), going to the “Styles” panel and looking at what CSS styles are being used. We can toggle properties on and off to see how they effect the paint times. This gives us much finer-grained insight into the paint profile of the page.

Here, we see that Pinterest is using box-shadow on these pins. We’ve optimized the performance of box-shadow in Chrome over the past two years, but in combination with other styles and when heavily used, it could cause a bottleneck, so it’s worth looking at.

Pinterest has reduced continuous paint mode times by 40% by moving box-shadow to a separate element that doesn’t have border-radius. The side effect is slightly fuzzy-looking corners; however, it is barely noticeable due to the color scheme and the low border-radius values.

Note: You can read more about this topic in “CSS Paint Times and Page Render Weight.”

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Toggling styles to measure their effect on page-rendering weight. Larger view.

Let’s disable box-shadow to see whether it makes a difference. As you can see, it’s no longer visible on any of the pins. So, let’s go back to the timeline and record a new session in which we scroll the same way as we did before (up and down, up and down, up and down). We’re getting closer to 60 FPS now, and that’s just from one change.

Public service announcement: We’re absolutely not saying don’t use box-shadow — by all means, do! Just make sure that if you have a performance problem, measure correctly to find out what your own bottlenecks are. Always measure! Your website or application is unique, as will any performance bottleneck be. Browser internals change almost daily, so measuring is the smartest way to stay up to date on the changes, and Chrome’s Developer Tools makes this really easy to do.

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Using Chrome Developer Tools to profile is the best way to track browser performance changes. Larger view.

Note: Eberhard Grather recently wrote a detailed post on “Profiling Long Paint Times With DevTools’ Continuous Painting Mode,” which you should spend some quality time with.

Another thing we noticed is that if you click on the “Repin” button, do you see the animated effect and the lightbox being painted? There’s a big red flash of repaint in the background. It’s not clear from the tooling if the paint is the white cover or some other affected being area. Be sure to double check that the paint rectangles correspond to the element or elements that you think are being repainted, and not just what it looks like. In this case, it looks like the whole screen is being repainted, but it could well be just the white cover, which might not be all that expensive. It’s nuanced; the important thing is to understand what you’re seeing and why.

Hardware Compositing (GPU Acceleration)

The last thing we’re going to look at on Pinterest is GPU acceleration. In the past, Web browsers have relied pretty heavily on the CPU to render pages. This involved two things: firstly, painting elements into a bunch of textures, called layers; and secondly, compositing all of those layers together to the final picture seen on screen.

Over the past few years, however, we’ve found that getting the GPU involved in the compositing process can lead to some significant speeding up. The premise is that, while the textures are still painted on the CPU, they can be uploaded to the GPU for compositing. Assuming that all we do on future frames is move elements around (using CSS transitions or animations) or change their opacity, we simply provide these changes to the GPU and it takes care of the rest. We essentially avoid having to give the GPU any new graphics; rather, we just ask it to move existing ones around. This is something that the GPU is exceptionally quick at doing, thus improving performance overall.

There is no guarantee that this hardware compositing will be available and enabled on a given platform, but if it is available the first time you use, say, a 3D transform on an element, then it will be enabled in Chrome. Many developers use the translateZ hack to do just that. The other side effect of using this hack is that the element in question will get its own layer, which may or may not be what you want. It can be very useful to effectively isolate an element so that it doesn’t affect others as and when it gets repainted. It’s worth remembering that the uploading of these textures from system memory to the video memory is not necessarily very quick. The more layers you have, the more textures need to be uploaded and the more layers that will need to be managed, so it’s best not to overdo it.

Note: Tom Wiltzius has written about the layer model in Chrome, which is a relevant read if you are interested in understanding how compositing works behind the scenes. Paul has also written a post about the translateZ hack and how to make sure you’re using it in the right ways.

Another great setting in Developer Tools that can help here is “Show composited layer borders.” This feature will give you insight into those DOM elements that are being manipulated at the GPU level.

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Switching on composited layer borders will indicate Chrome’s rendering layers. Larger view.

If an element is taking advantage of the GPU acceleration, you’ll see an orange border around it with this on. Now as we scroll through, we don’t really see any use of composited layers on this page — not when we click “Scroll to top” or otherwise.

Chrome is getting better at automatically handling layer promotion in the background; but, as mentioned, developers sometimes use the translateZ hack to create a composited layer. Below is Pinterest’s feed with translateZ(0) applied to all pins. It’s not hitting 60 FPS, but it is getting closer to a consistent 30 FPS on desktop, which is actually not bad.

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Using the translateZ(0) hack on all Pinterest pins. Note the orange borders. Larger view.

Remember to test on both desktop and mobile, though; their performance characteristics vary wildly. Use the timeline in both, and watch your paint time chart in Continuous Paint mode to evaluate how fast you’re busting your budget.

Again, don’t use this hack on every element on the page — it might pass muster on desktop, but it won’t on mobile. The reason is that there is increased video memory usage and an increased layer management cost, both of which could have a negative impact on performance. Instead, use hardware compositing only to isolate elements where the paint cost is measurably high.

Note: In the WebKit nightlies, the Web Inspector now also gives you the reasons for layers being composited. To enable this, switch off the “Use WebKit Web Inspector” option and you’ll get the front end with this feature in there. Switch it on using the “Layers” button.

A Find-and-Fix Workflow

Now that we’ve concluded our Pinterest case study, what about the workflow for diagnosing and addressing your own paint problems?

Finding the Problem

  • Make sure you’re in “Incognito” mode. Extensions and apps can skew the figures that are reported when profiling performance.
  • Open the page and the Developer Tools.
  • In the timeline, record and interact with your page.
  • Check for frames that go over budget (i.e. over 60 FPS).
  • If you’re close to budget, then you’re likely way over the budget on mobile.
  • Check the cause of the jank. Long paint? CSS layout? JavaScript?

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Spend some quality time with Frame mode in Chrome Developer Tools to understand your website’s runtime profile. Larger view.

Fixing the Problem

  • Go to “Settings” and enable “Continuous Page Repainting.”
  • In the “Elements” panel, hide anything non-essential using the hide (H) shortcut.
  • Walk through the DOM tree, hiding elements and checking the FPS in the timeline.
  • See which element(s) are causing long paints.
  • Uncheck styles that could affect paint time, and track the FPS.
  • Continue until you’ve located the elements and styles responsible for the slow-down.

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Switch on extra Developer Tools features for more insight. Larger view.

What About Other Browsers?

Although at the time of writing, Chrome has the best tools to profile paint performance, we strongly recommend testing and measuring your pages in other browsers to get a feel for what your own users might experience (where feasible). Performance can vary massively between them, and a performance smell in one browser might not be present in another.

As we said earlier, don’t guess it, test it! Measure for yourself, understand the abstractions, know your browser’s internals. In time, we hope that the cross- browser tooling for this area improves so that developers can get an accurate picture of rendering performance, regardless of the browser being used.

Conclusion

Performance is important. Not all machines are created equal, and the fast machines that developers work on might not have the performance problems encountered on the devices of real users. Frame rate in particular can have a big impact on engagement and, consequently, on a project’s success. Luckily, a lot of great tools out there can help with that.

Be sure to measure paint performance on both desktop and mobile. If all goes well, your users will end up with snappier, more silky-smooth experiences, regardless of the device they’re using.

Further Reading

About the Authors

Addy Osmani and Paul Lewis are engineers on the Developer Relations team at Chrome, with a focus on tooling and rendering performance, respectively. When they’re not causing trouble, they have a passion for helping developers build snappy, fluid experiences on the Web.

(al)

© Addy Osmani for Smashing Magazine, 2013.

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Todd Hoff

When you have a large population of servers you have both the opportunity and the incentive to perform interesting studies. Authors from Google and the University of California in Optimizing Google’s Warehouse Scale Computers: The NUMA Experience conducted such a study, taking a look at how jobs run on clusters of machines using a NUMA architecture. Since NUMA is common on server class machines it's a topic of general interest for those looking to maximize machine utilization across clusters.

Some of the results are surprising:

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Todd Hoff

What data structure is more sacred than the link list? If we get rid of it what silly interview questions would we use instead? But not using linked-lists is exactly what Aater Suleman recommends in Should you ever use Linked-Lists?

In The Secret To 10 Million Concurrent Connections one of the important strategies is not scribbling data all over memory via pointers because following pointers increases cache misses which reduces performance. And there’s nothing more iconic of pointers than the link list.

Here are Aeter's reasons to be anti-linked-list:

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Todd Hoff

Now that we have the C10K concurrent connection problem licked, how do we level up and support 10 million concurrent connections? Impossible you say. Nope, systems right now are delivering 10 million concurrent connections using techniques that are as radical as they may be unfamiliar.

To learn how it’s done we turn to Robert Graham, CEO of Errata Security, and his absolutely fantastic talk at Shmoocon 2013 called C10M Defending The Internet At Scale.

Robert has a brilliant way of framing the problem that I’ve never heard of before. He starts with a little bit of history, relating how Unix wasn’t originally designed to be a general server OS, it was designed to be a control system for a telephone network. It was the telephone network that actually transported the data so there was a clean separation between the control plane and the data plane. The problem is we now use Unix servers as part of the data plane, which we shouldn’t do at all. If we were designing a kernel for handling one application per server we would design it very differently than for a multi-user kernel. 

Which is why he says the key is to understand:

  • The kernel isn’t the solution. The kernel is the problem.

Which means:

  • Don’t let the kernel do all the heavy lifting. Take packet handling, memory management, and processor scheduling out of the kernel and put it into the application, where it can be done efficiently. Let Linux handle the control plane and let the the application handle the data plane.

The result will be a system that can handle 10 million concurrent connections with 200 clock cycles for packet handling and 1400 hundred clock cycles for application logic. As a main memory access costs 300 clock cycles it’s key to design in way that minimizes code and cache misses.

With a data plane oriented system you can process 10 million packets per second. With a control plane oriented system you only get 1 million packets per second.

If this seems extreme keep in mind the old saying: scalability is specialization. To do something great you can’t outsource performance to the OS. You have to do it yourself.

Now, let’s learn how Robert creates a system capable of handling 10 million concurrent connections...

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NewsBlur survives a traffic surge after news of Google Reader’s pending demise gets around.
Image: NewsBlur.

One of the more interesting stories to emerge from the demise of Google Reader is that of NewsBlur, a previously small, but very nice, open source alternative RSS reader.

NewsBlur is a one-man operation that was humming along quite nicely, but when Google announced Reader would shutdown, NewsBlur saw a massive traffic spike — in a few short days NewsBlur more than doubled its user base. How NewsBlur developer Samuel Clay handled the influx of new users should be required reading for anyone working on a small site without loads of funding and armies of developers.

“I was able to handle the 1,500 users who were using the service everyday,” writes Clay, “but when 50,000 users hit an uncachable and resource intensive backend, unless you’ve done your homework and load tested the living crap out of your entire stack, there’s going to be trouble brewing.”

Having tested NewsBlur a few times right after Google announced Reader was closing, I can vouch for the fact that there were times when the site was reduced to a crawl, but it came back to life remarkably quickly for a one-man operation.

In his postmortem, Clay details the moves he had to make to keep NewsBlur functioning under the heavy load — switching to new servers, adding a new mailing service (which then accidentally mailed Clay 250,000 error reports) and other moments of rapid, awkward growth.

It’s also worth noting that Clay credits the ability to scale to his premium subscription model, writing that, “the immediate benefits of revenue have been very clear over the past few days.”

As for the future, Clay says he plans to work on “scaling, scaling, scaling,” launching a visual refresh (which you can preview at dev.newsblur.com) and listening to feedback from the service’s host of new users.

If you’re looking for a Google Reader replacement, give NewsBlur a try. There’s a free version you can test out (the number of feeds is limited). A premium account runs $24/year and you can also host NewsBlur on your own server if you prefer.

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Social code hosting service GitHub isn’t just a free, easy way to host and share your code; it’s also a huge CSS and HTML testing ground with experience writing a fast, scalable code.

So what has GitHub learned from running a hugely successful site? That surprisingly small changes to both HTML and CSS can have a huge impact on performance.

GitHub’s Jon Rohan gave a talk about some of the service’s performance problems and solutions at the CSS Dev Conference in Honolulu earlier this year. (The slides are available on Speaker Deck.) The whole video is worth watching, but the key takeaway is that the right small changes in your code can have a huge impact on performance.

Many of Rohan’s suggestions for faster CSS will be familiar to anyone who’s used YSlow and other performance tools — get rid of unnecessary tag identifiers in your CSS, i.e., div.menu becomes just .menu, eliminate ancestors where possible and avoid chaining your CSS selectors.

On the HTML side — and Rohan says it’s here that GitHub really saw performance improvements — he suggests reducing the amount of matched HTML on the page. That is, look at your pages in a profiler, figure out which tags are being matched and look for ways to simplify the layout to avoid bottlenecks. Among the more depressing things Rohan presents is how much the page load times dropped with switching from anchor links to a JavaScript solution that, while faster, is considerably less accessible.

GitHub is undeniably different than most websites — especially pages like the Git diff views, which involve considerably more code than most pages will need. But, while GitHub may be the extreme example, in many cases the same small changes can help speed up much simpler pages as well.

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For all the sophisticated synthesis and remix tools out there, for a lot of musicians, the best thing sound technology can do is just give them a way to record and play. Looping is a simple technique – it involves recording a snippet of sound, playing it back, and then adding layers. But used masterfully, it can become transformative, producing rhythms and layers and letting solo artists accompany themselves.

“How do I get started looping?” is a question I hear from a lot of musicians, particularly those who are already expressive with their instruments and voice. There’s a technical answer to that question, involving something like the Loop Station from BOSS. But before you skip ahead to what to buy at your music store, it’s best to have some musical ideas.

And so, our weekend inspiration today comes from K Ishibashi aka Kishi Bashi, the Japanese-American virtuoso looper, who mixes a variety of instruments and spectacular, present voice. National Public Radio, the listener-supported broadcaster from the United States, has an intimate look at his work and shares the video above. It’s worth listening to the full radio piece (streaming worldwide free), as Kishi Bashi picks apart his process and explains what he’s doing.

Part of what I like best about what he’s doing is the rhythmic invention, in the snippets themselves and the layers. And even something as simple as doubling the speed can have a huge impact.

For those new to live looping techniques, it’ll be eye-opening. And even for more advanced loopers, Kishi Bashi’s chops should give you some encouragement to hone your craft.

Kishi Bashi: Unique Performances In Time

It inspires me to look for ways of covering looping and other live performance techniques better here. From Ableton’s built-in facility to homebrewed Pd patches to pedals and plug-ins and the lot, there are many angles one could take technically, even before the all-important musical issues. So if you have some ideas of what you’d like to see, let us know.

BOSS, for their part, has held international looping competitions to judge users of their ubiquitous pedal. But there are other ways to go, as well.

http://kishibashi.com

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