CoolInterview.com - World's Largest Collection of Interview Questions & Answers, FAQs, queries, sample papers, exam papers, dumps, what, why, how, where, when questions OneStopTesting.com - Testing EBooks, Tutorials, Articles, Jobs, Training Institutes etc.
OneStopGate.com - Gate EBooks, Tutorials, Articles, FAQs, Jobs, Training Institutes etc.
OneStopMBA.com - MBA EBooks, Tutorials, Articles, FAQs, Jobs, Training Institutes etc.
OneStopIAS.com - IAS EBooks, Tutorials, Articles, FAQs, Jobs, Training Institutes etc.
OneStopSAP.com - SAP EBooks, Tutorials, Articles, FAQs, Jobs, Training Institutes etc.
OneStopGRE.com - of GRE EBooks, Tutorials, Articles, FAQs, Jobs, Training Institutes etc.

Sponsored Links

Interview Questions
Our Services



INTERVIEW QUESTIONS PROGRAMMING LANGUAGES C DETAILS
Question :

What is page thrashing?

Category C Interview Questions
Rating (3.6) By 74 users
Added on 10/22/2009
Views 9108
Rate it!


Answers:

Source: CoolInterview.com

Some operating systems (such as UNIX or Windows in enhanced mode) use virtual memory. Virtual
memory is a technique for making a machine behave as if it had more memory than it really has, by using disk space to simulate RAM (random-access memory). In the 80386 and higher Intel CPU chips, and in most other modern microprocessors (such as the Motorola 68030, Sparc, and Power PC), exists a piece of hardware called the Memory Management Unit, or MMU.

The MMU treats memory as if it were composed of a series of ?pages.? A page of memory is a block of
contiguous bytes of a certain size, usually 4096 or 8192 bytes. The operating system sets up and maintains a table for each running program called the Process Memory Map, or PMM. This is a table of all the pages of memory that program can access and where each is really located.

Every time your program accesses any portion of memory, the address (called a ?virtual address?) is processed by the MMU. The MMU looks in the PMM to find out where the memory is really located (called the ?physical address?). The physical address can be any location in memory or on disk that the operating system has assigned for it. If the location the program wants to access is on disk, the page containing it must be read from disk into memory, and the PMM must be updated to reflect this action (this is called a ?page fault?).

Because accessing the disk is so much slower than accessing RAM, the operating system tries to keep as much of the virtual memory as possible in RAM. If you?re running a large enough program (or several small programs at once), there might not be enough RAM to hold all the memory used by the programs, so some of it must be moved out of RAM and onto disk (this action is called ?paging out?).
The operating system tries to guess which areas of memory aren?t likely to be used for a while (usually based on how the memory has been used in the past). If it guesses wrong, or if your programs are accessing lots of memory in lots of places, many page faults will occur in order to read in the pages that were paged out. Because all of RAM is being used, for each page read in to be accessed, another page must be paged out. This can lead to more page faults, because now a different page of memory has been moved to disk.

The problem of many page faults occurring in a short time, called ?page thrashing,? can drastically cut the performance of a system. Programs that frequently access many widely separated locations in memory are more likely to cause page thrashing on a system. So is running many small programs that all continue to run even when you are not actively using them. To reduce page thrashing, you can run fewer programs simultaneously. Or you can try changing the way a large program works to maximize the capability of the operating system to guess which pages won?t be needed. You can achieve this effect by caching values or changing lookup algorithms in large data structures, or sometimes by changing to a memory allocation library which provides an implementation of malloc() that allocates memory more efficiently. Finally, you might consider adding more RAM to the system to reduce the need to page out.

Source: CoolInterview.com



Source: CoolInterview.com

thrashing is a situation where large amounts of computer resources are used to do a minimal amount of work, with the system in a continual state of resource contention
Source: CoolInterview.com



Posted by: anil kumar

Contact anil kumar Contact anil kumar

If you have the better answer, then send it to us. We will display your answer after the approval.
Rules to Post Answers in CoolInterview.com:-
  • There should not be any Spelling Mistakes.
  • There should not be any Gramatical Errors.
  • Answers must not contain any bad words.
  • Answers should not be the repeat of same answer, already approved.
  • Answer should be complete in itself.
Name :*
Email Id :*
Answer :*
Verification Code Code Image - Please contact webmaster if you have problems seeing this image code Not readable? Load New Code
Process Verification Enter the above shown code: *
Inform me about updated answers to this question

Related Questions
View Answer
When should the register modifier be used? Does it really help?
View Answer
When should a type cast be used?
View Answer

Please Note: We keep on updating better answers to this site. In case you are looking for Jobs, Pls Click Here Vyoms.com - Best Freshers & Experienced Jobs Website.

View ALL C Interview Questions & Answers



User Options
India News Network

Latest 20 Questions
What is XML Element?
What is CDATA?
Who is responsible for XML?
What is an XML Schema?
What is well formed XML document?
Why XML has been used for development?
What is SGML?
What are the special characters used in XML?
What are the disadvantages of XML?
Why XSLT is important for XML?
What are nested elements in XML?
What is XQuery?
What is XLink and XPointer?
Why XML editor is needed instead of Notepad?
What is XML Encoding?
Which XML is set to be valid XML?
What is Simple Element?
What is Complex Element?
Is there a way to describe XML data?
What are the three parts of XSL?



Fresher Jobs | Experienced Jobs | Government Jobs | Walkin Jobs | Company Profiles | Interview Questions | Placement Papers | Companies In India | Consultants In India | Colleges In India | Exams In India | Latest Results | Notifications In India | Call Centers In India | Training Institutes In India | Job Communities In India | Courses In India | Jobs by Keyskills | Jobs by Functional Areas

Testing Articles | Testing Books | Testing Certifications | Testing FAQs | Testing Downloads | Testing Interview Questions | Testing Jobs | Testing Training Institutes

Gate Articles | Gate Books | Gate Colleges | Gate Downloads | Gate Faqs | Gate Jobs | Gate News | Gate Sample Papers | Gate Training Institutes

MBA Articles | MBA Books | MBA Case Studies | MBA Business Schools | MBA Current Affairs | MBA Downloads | MBA Events | MBA Notifications | MBA FAQs | MBA Jobs
MBA Job Consultants | MBA News | MBA Results | MBA Courses | MBA Sample Papers | MBA Interview Questions | MBA Training Institutes

GRE Articles | GRE Books | GRE Colleges | GRE Downloads | GRE Events | GRE FAQs | GRE News | GRE Training Institutes | GRE Sample Papers

IAS Articles | IAS Books | IAS Current Affairs | IAS Downloads | IAS Events | IAS FAQs | IAS News | IAS Notifications | IAS UPSC Jobs | IAS Previous Question Papers
IAS Results | IAS Sample Papers | IAS Interview Questions | IAS Training Institutes | IAS Toppers Interview

SAP Articles | SAP Books | SAP Certifications | SAP Companies | SAP Study Materials | SAP Events | SAP FAQs | SAP Jobs | SAP Job Consultants
SAP Links | SAP News | SAP Sample Papers | SAP Interview Questions | SAP Training Institutes |




Copyright ©2003-2016 CoolInterview.com, All Rights Reserved.
Privacy Policy | Terms and Conditions



Cache = 0.691406 Seconds