Java IoT Authors: Elizabeth White, Liz McMillan, Pat Romanski, Yeshim Deniz, Zakia Bouachraoui

Related Topics: @DevOpsSummit, Linux Containers, Containers Expo Blog

@DevOpsSummit: Blog Feed Post

The Speed Index | @DevOpsSummit @Catchpoint #DevOps #WebPerf #DX #AI

There’s a lot of buzz around the speed index metric, but what exactly is this metric and how is it calculated?

Understanding Speed Index
By Moiz Khan

There’s a lot of buzz around the speed index metric, but what exactly is this metric and how is it calculated? Even more so, why do we need a new metric when there are so many already on the plate? This article gives you detailed answers to these questions.

What is speed index?
User expectations have changed drastically, webpages are expected to load faster with all elements rendering as soon as possible; user frustration increases if the visual content of the page is slow to load.

There are several metrics used to measure user experience, but do these give us a clear enough picture? Not really. For example, render start indicates when the page started painting, but this could mean it loaded a white background, a random object, or just a dot on the page; the user, however, may still be looking at a blank page. The document complete metric, which flags the onLoad event, may not be important from an end user’s perspective as it considers below-the-fold requests as well; there could be instances where the Document complete is triggered even when the page is blank.

Speed Index is an abstract score that was introduced to overcome the limitations of the current set of metrics. It measures user experience and unlike render start or document complete, it is not a timing metric, therefore the smaller the score, the better it is. Speed index takes into account the visual completeness of the page above-the-fold. It does a much better job of measuring the perceived performance of a page, but does this mean other metrics are irrelevant? This is debatable. Instead, the choice of a metric depends on the scenario and the nature of the website being analyzed.

How relevant is speed index?
Speed index will let you know if the visible content is loading quickly or not. The lower the score, the better is the user experience, and vice versa. The speed index score indicates whether you need to optimize your page or not. To maintain a good score, there are two critical aspects that you should look at: optimizing content efficiency and optimizing the critical rendering path.

Web applications continue to grow in terms of functionality, scope, and usability; hundreds of resources make up these applications and fetching each resource adds to the page load time. Maintaining performance is possible only when the resources and content that make up the page are optimized. Speed index plays a critical role in monitoring the performance of visible content.

How is it calculated?
Speed index lets you measure how quickly a page’s content is visible. However, it can be a little tricky to understand what it means and what factors contribute to the score.

Speed index uses film strips to calculate the score, each frame is scored for visual completeness above the fold – the score is 0% for a blank screen and 100% for a visually complete screen. The score for each frame is calculated using this formula:

interval time*(1 – visual complete %/100)

The process is repeated for every frame and the cumulative of all the scores gives you the speed index of that page.

Let’s take an example:

Adding all of the scores gives the speed index score:

500 + 450 + 350 + 200 + 50 = 1550

Here is another example:

Let’s add up the score:

500 + 500 + 475 + 400 + 350 = 2225

From a performance point of view, the lower the score the better it is. There is no defined benchmark for speed index, however, a score of <1000 is considered good. User experience is better if above-the-fold content is displayed faster, and this is what speed index determines.

Measuring speed index using Catchpoint
To check speed index, you will need to enable the “Capture Filmstrip” option under Advanced Settings of a test. It is displayed along with other metrics in the charts, and you can also view it in the waterfall graphs. Here are a few examples that illustrate how pages that load the visual content faster have a better speed index score.

Example 1:

In the above example, the page has a good speed index score of 1260. If you look at the film strip, the interval is of 500ms, and from the second frame the visual content is visible, which is about 1 second. Frame three has almost all the content loaded. From a user’s point of view, we have engaged them from the very first second due to the fact that the page is optimized.

Example 2:

In the above image, the visual is visible in the third frame. The first two frames are blank, which is why the speed index score of 1741 is higher than the first example. The user views content at 1.6 seconds, unlike the first example where the user viewed the content within a second.

Example 3:

Based on the final example above, we are able to understand what is happening. The first two frames are blank and in the third frame visual content starts to load. However, the completeness is less compared to the other two images in the same frame. The visual content continues to load in the fourth frame, but it’s not complete until the fifth frame. This means that the user needs to wait for 1.6 seconds to see something on the page, and another 2.8 seconds to view the complete visual content.

In all of the examples, the render start is triggered before the user views anything on the page. In the second example, the render start happens at 1195ms and the visible content starts to load at 1604ms. In the third example, the render start happens at 1296ms and the visible content starts to load at 1597ms. This is the uniqueness of speed index. With a highly unoptimized website, the difference could be extremely high, with render start happening quickly but the visible content loads quite late. You need these insights to optimize your websites.

Limitations of Speed Index
When running transaction tests for dynamic sites or single page applications that use ajax, the score is always good in the steps that follow once the page is opened. This is because the page does not refresh after it is loaded. Pages featuring carousels that rotate automatically may be penalized because they continue to change even after the page load is completed.

Speed index indicates the visual completeness of the page; however, it does not indicate if the content was critical or non-critical for the user. As such, it should not be a replacement for other metrics and should be considered a rather useful and much-needed addition to the list of metrics. You will still need to look at render start and document complete to understand the overall performance. Speed index gives you a different perspective of the user experience that your site delivers.

The post Understanding Speed Index appeared first on Catchpoint's Blog - Web Performance Monitoring.

More Stories By Mehdi Daoudi

Catchpoint radically transforms the way businesses manage, monitor, and test the performance of online applications. Truly understand and improve user experience with clear visibility into complex, distributed online systems.

Founded in 2008 by four DoubleClick / Google executives with a passion for speed, reliability and overall better online experiences, Catchpoint has now become the most innovative provider of web performance testing and monitoring solutions. We are a team with expertise in designing, building, operating, scaling and monitoring highly transactional Internet services used by thousands of companies and impacting the experience of millions of users. Catchpoint is funded by top-tier venture capital firm, Battery Ventures, which has invested in category leaders such as Akamai, Omniture (Adobe Systems), Optimizely, Tealium, BazaarVoice, Marketo and many more.

IoT & Smart Cities Stories
In his session at 21st Cloud Expo, Raju Shreewastava, founder of Big Data Trunk, provided a fun and simple way to introduce Machine Leaning to anyone and everyone. He solved a machine learning problem and demonstrated an easy way to be able to do machine learning without even coding. Raju Shreewastava is the founder of Big Data Trunk (www.BigDataTrunk.com), a Big Data Training and consulting firm with offices in the United States. He previously led the data warehouse/business intelligence and Bi...
Contextual Analytics of various threat data provides a deeper understanding of a given threat and enables identification of unknown threat vectors. In his session at @ThingsExpo, David Dufour, Head of Security Architecture, IoT, Webroot, Inc., discussed how through the use of Big Data analytics and deep data correlation across different threat types, it is possible to gain a better understanding of where, how and to what level of danger a malicious actor poses to an organization, and to determin...
Nicolas Fierro is CEO of MIMIR Blockchain Solutions. He is a programmer, technologist, and operations dev who has worked with Ethereum and blockchain since 2014. His knowledge in blockchain dates to when he performed dev ops services to the Ethereum Foundation as one the privileged few developers to work with the original core team in Switzerland.
Cloud-enabled transformation has evolved from cost saving measure to business innovation strategy -- one that combines the cloud with cognitive capabilities to drive market disruption. Learn how you can achieve the insight and agility you need to gain a competitive advantage. Industry-acclaimed CTO and cloud expert, Shankar Kalyana presents. Only the most exceptional IBMers are appointed with the rare distinction of IBM Fellow, the highest technical honor in the company. Shankar has also receive...
Digital Transformation and Disruption, Amazon Style - What You Can Learn. Chris Kocher is a co-founder of Grey Heron, a management and strategic marketing consulting firm. He has 25+ years in both strategic and hands-on operating experience helping executives and investors build revenues and shareholder value. He has consulted with over 130 companies on innovating with new business models, product strategies and monetization. Chris has held management positions at HP and Symantec in addition to ...
"MobiDev is a Ukraine-based software development company. We do mobile development, and we're specialists in that. But we do full stack software development for entrepreneurs, for emerging companies, and for enterprise ventures," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
Cloud computing delivers on-demand resources that provide businesses with flexibility and cost-savings. The challenge in moving workloads to the cloud has been the cost and complexity of ensuring the initial and ongoing security and regulatory (PCI, HIPAA, FFIEC) compliance across private and public clouds. Manual security compliance is slow, prone to human error, and represents over 50% of the cost of managing cloud applications. Determining how to automate cloud security compliance is critical...
Enterprises have taken advantage of IoT to achieve important revenue and cost advantages. What is less apparent is how incumbent enterprises operating at scale have, following success with IoT, built analytic, operations management and software development capabilities - ranging from autonomous vehicles to manageable robotics installations. They have embraced these capabilities as if they were Silicon Valley startups.
Recently, REAN Cloud built a digital concierge for a North Carolina hospital that had observed that most patient call button questions were repetitive. In addition, the paper-based process used to measure patient health metrics was laborious, not in real-time and sometimes error-prone. In their session at 21st Cloud Expo, Sean Finnerty, Executive Director, Practice Lead, Health Care & Life Science at REAN Cloud, and Dr. S.P.T. Krishnan, Principal Architect at REAN Cloud, discussed how they built...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things'). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing. IoT is not about the devices, its about the data consumed and generated. The devices are tools, mechanisms, conduits. This paper discusses the considerations when dealing with the...