'Prefetching' scheme saves time, energy

 

Connecting state and local government leaders

Researchers have figured out a way to maintain access to data on a computer hard disk that has powered down to conserve energy.

Most desktop computers today power down their hard drives when not in use to save energy. While this may be energy efficient, it also incurs minor, though sometimes frustrating, delays. Waiting as long as eight seconds for a hard drive to power back up to retrieve a document is not the best use of any office worker's time. So two University of Arizona researchers have figured out a way to save energy and maintain access to data through a concept they call 'context-aware prefetching.'

"The idea is to reduce or eliminate delays," said Igor Crk, who along with Chris Gniady wrote up their findings in the paper titled "Context-Aware Mechanisms for Reducing Interactive Delays of Energy Management in Disks." Crk presented the team's work at the Usenix conference held last month in Boston.

The idea is to run a small program that logs user actions and notes which chains of actions typically lead to interactions with the hard disk. For example, if a user opens a word processing program and then executes a series of keystrokes to open a document, that whole series of actions is a good predictor that the hard drive will need to deliver a file in a few seconds.

"Monitoring user interactions with applications provides an opportunity for predicting upcoming power mode transitions and, as a result, eliminating the delays associated with these transitions," the paper states.

The team wrote a program that, when sensing a sequence of actions that typically leads to hard-drive use, will issue a command to the hard drive to spin-up. So, by the time the user actually requests the file, the hard drive, already up and running, can return it immediately.

Prefetching is widely used in many systems, but in most of these approaches, the hard drive is activated whenever a user does anything at all on a computer. Only when the user does not interact with the computer for a set period of time does the disk power down. Crk explained that this approach is not as efficient insofar the hard drive stays powered on for long periods of time while nothing is actually written or read from the disk.

The team's approach accurately predicted hard-drive usage 79 percent of the time. As a result, this approach "is able to reduce spin-up delays on average by 35 percent (more than 3 seconds), while maintaining low energy consumption," according to the paper. By contrast, traditional prefetching predicted hard drive use 81 percent of the time, although it incorrectly predicted usage 52 percent of the time, making that approach much more energy-intensive.

Crk, speaking with GCN after the presentation, noted that context-aware prefetching could be easily implemented in most operating systems. Most all commercial hard drives have commands that be evoked to spin up disks. Crk explained that the program they created consumed very little in the way of CPU resources, so it would go unnoticed by users. (The program is available for those willing to sign a nondisclosure agreement and only use for the software for non-commercial use.)

Crk also said that this technique could also be used with wireless cards, which could help save battery life on mobile and laptop computers. The idea would be the same, though the program would wake up the wireless communications card rather than the hard drive.

Usenix, the Advanced Computing Systems Association, is a nonprofit association for technicians, scientists, systems administrators and engineers to share information on developments in the field of computer science.

NEXT STORY: askSam Professional

X
This website uses cookies to enhance user experience and to analyze performance and traffic on our website. We also share information about your use of our site with our social media, advertising and analytics partners. Learn More / Do Not Sell My Personal Information
Accept Cookies
X
Cookie Preferences Cookie List

Do Not Sell My Personal Information

When you visit our website, we store cookies on your browser to collect information. The information collected might relate to you, your preferences or your device, and is mostly used to make the site work as you expect it to and to provide a more personalized web experience. However, you can choose not to allow certain types of cookies, which may impact your experience of the site and the services we are able to offer. Click on the different category headings to find out more and change our default settings according to your preference. You cannot opt-out of our First Party Strictly Necessary Cookies as they are deployed in order to ensure the proper functioning of our website (such as prompting the cookie banner and remembering your settings, to log into your account, to redirect you when you log out, etc.). For more information about the First and Third Party Cookies used please follow this link.

Allow All Cookies

Manage Consent Preferences

Strictly Necessary Cookies - Always Active

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Sale of Personal Data, Targeting & Social Media Cookies

Under the California Consumer Privacy Act, you have the right to opt-out of the sale of your personal information to third parties. These cookies collect information for analytics and to personalize your experience with targeted ads. You may exercise your right to opt out of the sale of personal information by using this toggle switch. If you opt out we will not be able to offer you personalised ads and will not hand over your personal information to any third parties. Additionally, you may contact our legal department for further clarification about your rights as a California consumer by using this Exercise My Rights link

If you have enabled privacy controls on your browser (such as a plugin), we have to take that as a valid request to opt-out. Therefore we would not be able to track your activity through the web. This may affect our ability to personalize ads according to your preferences.

Targeting cookies may be set through our site by our advertising partners. They may be used by those companies to build a profile of your interests and show you relevant adverts on other sites. They do not store directly personal information, but are based on uniquely identifying your browser and internet device. If you do not allow these cookies, you will experience less targeted advertising.

Social media cookies are set by a range of social media services that we have added to the site to enable you to share our content with your friends and networks. They are capable of tracking your browser across other sites and building up a profile of your interests. This may impact the content and messages you see on other websites you visit. If you do not allow these cookies you may not be able to use or see these sharing tools.

If you want to opt out of all of our lead reports and lists, please submit a privacy request at our Do Not Sell page.

Save Settings
Cookie Preferences Cookie List

Cookie List

A cookie is a small piece of data (text file) that a website – when visited by a user – asks your browser to store on your device in order to remember information about you, such as your language preference or login information. Those cookies are set by us and called first-party cookies. We also use third-party cookies – which are cookies from a domain different than the domain of the website you are visiting – for our advertising and marketing efforts. More specifically, we use cookies and other tracking technologies for the following purposes:

Strictly Necessary Cookies

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Functional Cookies

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Performance Cookies

We do not allow you to opt-out of our certain cookies, as they are necessary to ensure the proper functioning of our website (such as prompting our cookie banner and remembering your privacy choices) and/or to monitor site performance. These cookies are not used in a way that constitutes a “sale” of your data under the CCPA. You can set your browser to block or alert you about these cookies, but some parts of the site will not work as intended if you do so. You can usually find these settings in the Options or Preferences menu of your browser. Visit www.allaboutcookies.org to learn more.

Sale of Personal Data

We also use cookies to personalize your experience on our websites, including by determining the most relevant content and advertisements to show you, and to monitor site traffic and performance, so that we may improve our websites and your experience. You may opt out of our use of such cookies (and the associated “sale” of your Personal Information) by using this toggle switch. You will still see some advertising, regardless of your selection. Because we do not track you across different devices, browsers and GEMG properties, your selection will take effect only on this browser, this device and this website.

Social Media Cookies

We also use cookies to personalize your experience on our websites, including by determining the most relevant content and advertisements to show you, and to monitor site traffic and performance, so that we may improve our websites and your experience. You may opt out of our use of such cookies (and the associated “sale” of your Personal Information) by using this toggle switch. You will still see some advertising, regardless of your selection. Because we do not track you across different devices, browsers and GEMG properties, your selection will take effect only on this browser, this device and this website.

Targeting Cookies

We also use cookies to personalize your experience on our websites, including by determining the most relevant content and advertisements to show you, and to monitor site traffic and performance, so that we may improve our websites and your experience. You may opt out of our use of such cookies (and the associated “sale” of your Personal Information) by using this toggle switch. You will still see some advertising, regardless of your selection. Because we do not track you across different devices, browsers and GEMG properties, your selection will take effect only on this browser, this device and this website.