How extended (4MB) and regular (4KB) paging coexist?
On x86 style, "Extended paging" permits web page structures (physical memory) to be 4 megabytes as opposed to 4 KB.
Guide "Understanding the Linux Kernel, 3rd" at phase 2 "Memory Addressing", below - phase "Paging in Linux", area "Kernel Page Tables", clarifies that for the last bit Page Table when RAM dimension is much less than 896 MEGABYTES:
] the bit can resolve the RAM by taking advantage of huge web pages (see the area "Extended Paging" previously in this phase).
Nonetheless, in the area "Extended Paging" (below - phase "Paging in Hardware"), it is created:
Extended paging coexists with normal paging.
I do not in fact get just how extensive and also normal paging exist side-by-side. Can please a person clarify those inquiries:
- In which instances the bit makes use of 4 megabytes web pages? or 4 KB web pages?
- Which web page structure dimension will be made use of for kmalloc procedures? for vmalloc?
- If we think that the first code & information (bit is sectors, provisionary Page Tables, and also 128 KB for vibrant information) suit the first 8 megabytes of RAM (as the instance offered by the publication), what happens if the actual quantity of code & information is 5MB just: will the bit waste 8 - 5 = 3 MEGABYTES?