What is the difference between user space and kernel space?
Kernel space is that area of virtual memory where kernel processes will run and user space is that area of virtual memory where user processes will be running.
What is true for Slab in terms of allocating kernel memory?
A second strategy for allocating kernel memory is known as slab allocation. It eliminates fragmentation caused by allocations and deallocations. This method is used to retain allocated memory that contains a data object of a certain type for reuse upon subsequent allocations of objects of the same type.
How do I go from user space to kernel space?
System Call Interfaces (SCI) are the only way to transit from User space to kernel space. Kernel space switching is achieved by Software Interrupt, which changes the processor mode and jump the CPU execution into interrupt handler, which executes corresponding System Call routine.
How is slab allocator implemented?
Set the parameter as 1 to allocate with malloc(), 2 with the slab allocator….Example & benchmark.
| Size of an object in bytes | malloc() | slab allocator |
|---|---|---|
| 48 | 68.7 Mio | 54.0 Mio |
| 64 | 83.9 Mio | 70.2 Mio |
| 128 | 145.0 Mio | 135.2 Mio |
| 256 | 266.9 Mio | 271.0 Mio |
Is kernel space in RAM?
The code for managing all this hardware – all the shared resources, as well as process scheduling and memory management – is located in main memory and belongs to the oper- ating system. This part of the main memory is what is commonly referred to as kernel space.
What is kernel slab cache?
The basic idea behind the slab allocator is to have caches of commonly used objects kept in an initialised state available for use by the kernel. Each cache maintains blocks of contiguous pages in memory called slabs which are carved up into small chunks for the data structures and objects the cache manages.
What is slab in Linux kernel?
What Is a Slab Page? Slab allocation is a form of memory management, within the Linux kernel, used with the intention of making memory allocation of objects efficient. This type of memory management reduces fragmentation caused by allocations and deallocations.
What is required to change the mode from kernel to user?
The only way an user space application can explicitly initiate a switch to kernel mode during normal operation is by making an system call such as open, read, write etc. Whenever a user application calls these system call APIs with appropriate parameters, a software interrupt/exception(SWI) is triggered.
What is Linux kernel slab?
Where is mmap used?
The mmap() function can be used to map a region of memory that is larger than the current size of the object. Memory access within the mapping but beyond the current end of the underlying objects may result in SIGBUS signals being sent to the process.
Is mmap page aligned?
Quoated: In contrast address returned by mmap is only guaranteed to be page-aligned.