Multi level paging

Question

Im confused with multi level paging

As per my understanding the outer most page table must be in main memory and not all inner page tables to be in memory in 2 level paging by this we can save the memory

But with this, faults will be more and time gets increased 

Suppose

If the instruction belongs to page table 2 and if the main memory has page table directory and page table -1 and 3 

Here page table 2 is not available in memory so first we get page table from secondary memory and then have the fram details so that time taken will be high if we use more levels of paging more faults wil be their 

Even then why we are using multi level paging

Please can someone help me

Answer 1

First thing we don't know how things are implemented actually we just study multilevel paging in general, second thing is paging is a trade-off when our page table overhead is large and search time is also large then we use multilevel paging to reduce search time and paging overhead. In exchange of reduced search time and paging overhead we are gaining main memory access time because for each level we have to access memory.

Coming to your question that if page table 2 is not in memory then?

Take a real life example usually games have larger memory demand but system memory is limited to 4gb(8,16,32) then also we are able to play games, what paging does is it gives false ideas to process that system has enough memory so that we can run process who's size is larger then main memory so even if page fault occurs it is desirable rather then not running programming at all

Comments

Sir I got your point
When we solve problems regarding multilevel paging, outer level page must be memory and should we assume inner level page is with in memory or we also need to consider about page table fault

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If not mentioning any thing else regarding page fault, then consider all pages in main memory

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If we take in that way then multi level paging takes more memory than flat page

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What do you mean by flat page