Home > Articles > Information Technology

  • Print
  • + Share This
This chapter is from the book

3.5 Tuning or Upgrading

Once the bottleneck is identified, there are two choices. Either the amount of the resource can be increased, or the demand for the resource can be reduced. Tuning techniques will be discussed along with the particular bottlenecks. However, there are some general tips that can be applied to tuning bottlenecks:

  • Determine whether the data indicate a particular bottleneck.

  • Devise a simple test for measuring results.

  • Do not tune randomly.

  • Use heuristics and logic in choosing what to tune.

  • Look for simple causes.

  • Develop an action plan.

  • Change only one thing at a time.

  • Prioritize the goals.

  • Know when to stop tuning.

3.5.1 Determine Whether There Is a Particular Bottleneck

This is the first tip to apply. Using the multiple characteristics of a bottleneck, determine if the data indicate a particular bottleneck. There is no use in tuning disk I/O on a system that is CPU-bound.

3.5.2 Devise a Simple Test for Measuring Results

When something in the operating system or application is tuned, it is advisable to quantitatively measure whether performance has improved or degraded. The test should be simple, short, and repeatable, so that it can be performed as each tuning step is taken.

3.5.3 Do Not Tune Randomly

There was once a system administrator who always tuned the size of the buffer cache, no matter what the bottleneck. Tuning the wrong thing can make the situation worse rather than better. Use knowledge of how the kernel works to help decide the cause of the bottleneck. Always try to visualize what the data should look like and compare it to the actual data before assuming that a cause has been found.

3.5.4 Use Heuristics and Logic

Use heuristics to select the most likely cause of the bottleneck. Experience can point to a particular bottleneck rather quickly. Watching the access lights on the disk drives can quickly indicate which disk drives may be saturated even before you look at the metrics. Use the qualitative measures as well as the quantitative metrics. Logically work through the possible causes and potential tuning solutions. Experience in tuning systems will tell which tuning alternatives offer the largest probability of success.

3.5.5 Look for Simple Causes

By looking for simple causes, easier and less expensive solutions can be tried. This is the K. I. S. S. principle: Keep it Simple, Stupid! Simple causes tend to occur more frequently, and simple solutions should be tried first. For example, tuning a system parameter is easier and less costly than modifying the design of an application. Either tactic might result in performance improvements, but one is clearly a better solution than the other.

3.5.6 Develop an Action Plan

Write up an ordered, prioritized list of measurements and tuning actions. The list can sometimes be turned over to other people for execution. Include contingencies in case some of the steps do not result in improvement. Analyze the results after performing each step of the plan.

3.5.7 Change Only One Thing at a Time!

Otherwise, the cause of the bottleneck cannot be found. If you attempt to tune multiple things at once, the benefits from one type of tuning can be counteracted by the degradation caused by a different type of tuning.

3.5.8 Prioritize Goals

Often, you may have multiple goals when developing a tuning solution. Prioritizing the goals can solve the problem caused by different goals requiring different solutions. It is usually possible to tune for response time or for throughput, but not both. In a transaction-processing environment, one should tune for the most frequent type of transaction, or the most important.

3.5.9 Understand the Limits of the Application's Architecture

Some applications cannot fully utilize a system. An example is a single-threaded process flow designed with no parallelism. Adding a CPU to such an application may not increase performance.

Instrumenting an application (adding code to measure specific events or code paths) to provide performance metrics can also create this problem if the instrumentation is not created with parallelism in mind. For example, incrementing a single global counter may be a choke point, as in the following code design:


while not done {
    do transaction work
    lock
    increment global counter
    unlock
    }

3.5.10 Know When to Stop

Finally, knowing when to stop tuning is very important. Setting the performance expectations in advance is the easiest way to establish completion. Getting the user to agree to success criteria in advance is important for deciding not only when to stop tuning, but when you can declare success. Baselines can be used to help establish that performance has returned to a normal level. The "eternal hope syndrome" will not occur if the performance expectations are met through tuning.

From Bob's Consulting Log— I spent several days at a customer site improving performance by a factor of 50%. Once the customer saw the extent of the improvement, she insisted I do additional work to improve things even more. Soon it became clear that we had already maxed out the performance improvement and then wasted several more days trying to eke out just a little bit extra.

It is not useful to spend a lot of time on gaining 1% improvement in performance. Optimizing a part of the application that is executed only once and consumes less than 5% of the total execution time is just not worth it.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020