In this blog post, we will discover some possible causes that can cause kernel swapping in Linux, and then I will share possible ways to try to fix this problem.
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The kernel uses paging and paging to handle this memory management. Paging refers to the time it takes to write portions, called pages, of each process’s memory to disk. Simply put, swapping means writing the entire process, not just parts of it, back to disk.
In the fifth part of the list of
Linux kernel boot processes, we learned what the kernel does at the initial stage. In the third step, the kernel initializes individual things like
initrd mounting, lockdep initialization, and many other things before we can see the kernel actually start the first initialization process.
Yes, there will be a lot of different things, but rather a lot a lot and again a lot of work with memory.
What is the use of paging in Linux?
Linux uses demand paging directly to load executable images into a process’s virtual memory. Every time the command is executed,the file containing it can be considered open, and its contents are written to the process’s virtual memory.
In my opinion, storage management is one of the many complex parts of the Linux kernel that is widely used in systems programming. For this reason, before starting to initialize the kernel, we need to familiarize ourselves with paging.
Paging is a mechanism for converting a linear memory address And to a physical address. If you’ve read the previous parts of this book, your company may remember that we saw the actual segmentation method, where physical addresses were calculated by shifting the register of the partition by four and adding the best shift. We also saw segmentation in protected mode when we took a handle to a person and completely converted base addresses from offset descriptors to tables to compute some physical addresses. Now we understand paging in 64-bit mode.
What is demand paging in Linux?
On-demand paging is a type of replacement performed on virtual storage systems. With demand paging, data is unlikely to be copied from disk to a specific RAM until it is needed, that is, it is not requested by the program. Data will not be copied if it already exists in memory.
As the Intel manual says:
Paging provides a mechanism, in the implementation of a traditional on-demand virtual memory program, whereby portions of the program’s deployment environment are mapped to a physical memory region as needed.
What is kernel memory in Linux?
You see, Linux kernels share 4 GB of address space between user policies and the kernel; In your most common configuration, the full 3 GB of 32-bit space is allocated to user memory, and the main kernel gets the last 1 GB, which accumulates at 0xc0000000.
So… In this article I will try to explain the reasons for pagination. Of course, it will probably be closely related to this
x86_64 version of the Linux kernel, but we won’t go into details anyway (at least not in this article).
What is a kernel paging request?
A paging request or page fault is your way of telling the CPU that not all certain pages are mapped to each of our virtual memory.
There are three pagination mode:
Here we will interpret only the last mode. To control the paging mode of
IA-32e, almost everyone needs to do the following:
We have already seen where many of the bits were set in arch/x86/boot/compressed/head_64.S:
movl $(X86_CR0_PG | X86_CR0_PE), %eaxmovl %eax, %cr0
movl $MSR_EFER, %ecxRDMbcl $_EFER_LME, %eaxtimer
Paging divides a linear address space into web pages of a fixed size. Pages can be mapped to a specific physical address space or additional memory. This fixed size is
x86_64 of the Linux kernel. Special structures are used to perform linguistic translation linearly from address to physical solution. Each rule consists of
512 entries (mainly for
IA32_EFER and .LME modes). Swap structures are hierarchical and Linux, like the kernel, uses 4 swap levels in the
x86_64 architecture. The processor uses the line guard portion to identify an entry in the multi-user paging structure that is at a lower level, a state of physical memory (
page frame) or a physical address in my area (
page offset ). The address is a top-level swap structure strategically located in the
cr3 register. I had when I saw this in arch/x86/boot/compressed/head_64.S:
actual table pgtable(%ebx), %eaxmovl %eax, %cr3
We create the web publishing table structures and put the top level structure in the
cr3 register. Here it is recommended to store
cr3 in some top-level structure,
PML4 or just
global catalog page if it is in the Linux kernel.
cr3 is actually a 64-bit register and has the following structure:
63 42 tommers skrrrm 51 32 -------------------------------------------------- ------------------------------| | || Reserved by MBZ | AddressStructures of the upper level of a person || | | -------------------------------------------------- ------------------------------31 12 11 Download this software now to clean up your computer.