This algorithm should not be confused with the Multilevel Queue Scheduling Algorithm as the two are different. The later is not as flexible because processes are fixed and do not move between queues in the scenario where high-level and low-level processes exist.

The MLFQ scheduling algorithm offers much more flexibility because it enables a process to transfer to other queues which avoids the issue of starvation. Basically, what happens if a high-priority queue exceeds allotted CPU time, the algorithm will push that process to a lower-priority queue and vice versa (Silberschatz, Galvin, & Gagne, 2012, pp. 198).

One item to consider when reviewing MLFQ scheduling algorithms is that the scheduler will typically run all queues in order from 0 to X, where X is the number of the last queue. Queue 0 has the highest priority and X would have the lowest priority. However, if a process initiates in the higher-level priority queue slots, that will move the execution back to those queues and then it will move forward towards the lowest priority queue (Silberschatz et al. 2012, pp. 198).

Silberschatz et al. provided a great example and diagram that illustrated some of the complexities of how this particular algorithm performs using a 3 queue model. In their explanation, they indicated:

• Each queue contains one or more processes.
• If a process in the first queue (queue 0) exceeded its time allocation (8 milliseconds), it gets pushed to the end of queue 1.
• In this case, the first process in queue 1 will double (assuming queue 0 does not have any processes).
• If the first process in queue 1 does not finish, it gets pushed to the next queue, queue 2 which are executed by a First-Come, First-Served (FCFS) scheduling algorithm. But again, only if the prior queues 0 and 1 do not have any processes executing (Silberschatz et al. 2012, pp. 198).

The MLFQ scheduling algorithm involves a number of properties, namely: a) designating the quantity of queues involved, b) the algorithm assigned to a specific queue to help it effectively function for a specific task, c) a conditional aspect dictating when a process should be moved to a foreground or background process, or somewhere in-between (Silberschatz et al. 2012, pp. 199).

While MLFQ is a great algorithm that effectively reduces starvation, it is not perfect and instances of the latter do occur, especially when we see prolonged spikes utilizing high-priority queues with new incoming processes entering these queues. Demands for context-switching and memory usage increase when this happens, leading to a reduction of CPU utilization (Hoganson, 2009).

Hoganson indicated in his paper, Reducing MLFQ Scheduling Starvation with Feedback and Exponential Averaging that some people have tried to alleviate starvation by utilizing “real-time processing” principles, improving context switching, introducing a degree of artificial intelligence and experimenting with “neural network processing” (Hoganson, 2009). In his paper, he went on to propose another solution involving taking away processing time between high and low priorities queues and placing select processes occurring in this location to the low priority queue, so long as critical processes were not impacted. Hoganson added that his strategy should not be used if there are temporary processing spikes which he was able to measure and control in his enhanced MLFQ algorithm proposal. His proposal seems promising but it would not completely remove the risk of starvation during peak CPU usage periods where we see spikes. However, as mentioned before, while no algorithm or enhancement is perfect, if the positives of an alternate implementation outweigh the negative aspects and the proposed new solution has been fully tested and accepted by other researchers in the industry, it would be a logical positive step forward. Perhaps Hoganson’s solution could lead to the virtual elimination of starvation risk in the future, resulting with faster, more efficient systems.

References

Hoganson, K. (2009, Dec.). Reducing MLFQ scheduling starvation with feedback and exponential
     averaging. Journal of Computing Sciences in Colleges, 25(2), 196-202. Retrieved from ACM
     Digital Library.

Silberschatz, A., Galvin, P.B., & Gagne, G. (2012). Operating System Concepts Update (8th ed.).
     Hoboken, NJ: John Wiley & Sons, Inc.

References

Linux / Unix Command: top. (2012). Retrieved April 14, 2012, from
     http://linux.about.com/od/commands/l/blcmdl1_top.htm

Red Hat Enterprise Linux 3: Introduction to System Administration. (2012). Retrieved April 14, 2012, from
     http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/3/html/Introduction_to_System_Administration/s1-resource-rhlspec.html

TaskList.org. (2012). Retrieved April 14, 2012, from http://www.tasklist.org

Task Manager Overview. (2012). Retrieved April 14, 2012, from
     http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/taskman_whats_there_w.mspx?mfr=true

The Mac Task Manager. (2012). Retrieved April 14, 2012, from
     http://osxdaily.com/2010/08/15/mac-task-manager/

Unix Top. (2012). Retrieved April 14, 2012, from http://www.unixtop.org/man.shtml

What is Activity Monitor (or How to Take your Mac’s Pulse). (2012). Retrieved April 14, 2012, from
     http://macdevcenter.com/lpt/a/6248

ASPCA Animated Ad in Google Search Results
(Click on image for full view.)

My girlfriend noticed this as she was searching for a product on Google tonight, May 3, 2012 around 11:30 PM EST. I was unable to see this on two other laptops at home so it appears Google may be slowly rolling out this functionality. Apparently, the ads display beside select listings in search results and we saw them appear with the following queries:

• clinique exfoliating scrub
• reversa eye care
• Estee Lauder Smoothing Creme Concealer

These were just a few queries she typed at the time so of course, other queries would likely display the animation as well, if Google has rolled out the advertising feature with your account. She was using the Firefox web browser.

The dog beside one of the listings was animated and ‘ran’ off the screen which was very interesting. If Google ends up extending this functionality to all advertisers, this would certainly be a great revenue driver for Google and, with the additional visibility, could help convert more leads for advertisers.

Google has a similar ‘call out’ graphic for advertisers at the moment, but only if they purchase AdWords ads that appear in the right column of organic search results (or above and below these results). If the advertisers use Google Checkout, a Google Checkout button appears below their ad, making it stand out better among other ads.

It will be interesting to see how this develops.

Off topic, thought it would be nice to link to the ASPCA donation page. Many homeless pets do need proper care to survive.

UPDATE – May 4, 2012, 11:37 PM
Upon further investigation, it appears a Firefox extension called We-Care Reminder was installed by another program/process without my girlfriend’s knowledge. This extension places ads within Google organic search results and various web sites to help encourage charitable donations. Not actually tied to Google or their AdWords program in any way as We-Care Reminder is a browser extension that incorporates additional functionality to web sites.

While Windows 8 may not immediately be popular with most desktop PC and laptop users using non-touch-screen hardware, Microsoft likely realizes many of these users will inevitably upgrade to newer technology at some point that could feature a touch-screen monitor.  At that time, these users might like to trial the Metro UI features which could offer enhanced productivity and an overall improved user experience.  On the other hand, with or without a touch-screen monitor, some users may still prefer to use the Windows interface they are familiar with and have been using for years.  The two versions of Windows gives the consumer/business user options where they can select the best one that meets their needs and objectives.

From my perspective, Microsoft may not feel the user is ready to make a ‘hard switch’ to the new interface so wants to make a soft transition with the two versions.  Ultimately, I believe Microsoft will phase out the current Windows 7-style interface and go exclusively with the Metro UI interface.  This transition may not occur until many years in the future but would be a logical track in light of hardware and software vendors pushing towards ‘the cloud’.  Many of the leading software companies are porting all of their desktop applications to the Internet to streamline usability, accessibility, updates and security.  Hardware vendors have started to reduce the dependency of a physical hard drive (for applications and user file storage) by introducing netbooks such as Google’s Chromebook and hardware overall is becoming thinner and lighter.  Apple  has already removed the CD/DVD drive in their MacBook Air model.

Microsoft undoubtedly wants to tap a greater share of the smartphone/cloud-based application market that exists with Google Android devices and Apple iPhones.  An eventual forced move to the Metro UI version would help the company monetize this area and the benefit to the consumer/business user is it would allow them to have instant access to cloud-based applications on their computer with all the benefits.  For instance, the user would no longer need to worry so much about backing up their data, applications, etc. if it is all stored online.  Access from any Internet-enabled device is also a desirable benefit to the user.

Developers currently would need to develop an application for both versions of Windows 8 which requires additional time and resources (Bradley, 2011).  This negatively impacts the rate in which the Microsoft Windows 8 could become popular.  If developers only had to program one application and developer tools could instantly port that version for the traditional interface and the Metro UI version, Windows 8 would be an instant win in my opinion.  In order for a product to have success, developers and the end-user need to be happy.  One could argue that if it took less time for a developer to push applications to both versions of Windows, more users would be attracted to Windows as more applications would be available to them, no matter what version they decide to use with access to the same core benefits of the O/S.

References

Bradley, T. (2011, Dec. 8). Windows 8: One OS to rule them all? Retrieved from http://www.pcworld.com/businesscenter/article/245756/windows_8_one_os_to_rule_them_all.html

Esposito, D. (2011, Nov. 14). Win 8: No need to panic. Retrieved from http://search.proquest.com.ezproxy.snhu.edu/docview/904423994?accountid=3783