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Non-uniform memory access (NUMA) is a computer memory design used in multiprocessing, where the memory access time depends on the memory location relative to the processor. Under NUMA, a processor can access its own local memory faster than non-local memory. The benefits of NUMA are limited to particular workloads, notably on servers where the data is often associated strongly with certain tasks or users.
stat is a Unix system call that returns file attributes about an inode. The semantics of stat vary between operating systems. As an example, Unix command ls uses this system call to retrieve information on files that includes:
The Direct Rendering Manager (DRM) is a subsystem of the Linux kernel responsible for interfacing with GPUs of modern video cards. DRM exposes an API that user-space programs can use to send commands and data to the GPU and perform operations such as configuring the mode setting of the display. DRM was first developed as the kernel-space component of the X Server Direct Rendering Infrastructure, but since then it has been used by other graphic stack alternatives such as Wayland and standalone applications and libraries such as SDL2 and Kodi.
LWN.net is a computing webzine with an emphasis on free software and software for Linux and other Unix-like operating systems. It consists of a weekly issue, separate stories which are published most days, and threaded discussion attached to every story. Most news published daily are short summaries of articles published elsewhere, and are free to all viewers. Original articles are usually published weekly on Thursdays and are available only to subscribers for two weeks, after which they become free as well. LWN.net is part of Eklektix, Inc.
debugfs is a special file system available in the Linux kernel since version 2.6.10-rc3. It was written by Greg Kroah-Hartman.
The Completely Fair Scheduler (CFS) is a process scheduler that was merged into the 2.6.23 release of the Linux kernel and is the default scheduler of the tasks of the SCHED_NORMAL class. It handles CPU resource allocation for executing processes, and aims to maximize overall CPU utilization while also maximizing interactive performance.
Con Kolivas is an Australian anaesthetist. He has worked as a computer programmer on the Linux kernel and on the development of the cryptographic currency mining software CGMiner. His Linux contributions include patches for the kernel to improve its desktop performance, particularly reducing I/O impact.
Kernel markers were a static kernel instrumentation support mechanism for Linux kernel source code, allowing special tools such as LTTng or SystemTap to trace information exposed by these probe points. Kernel markers were declared in the kernel code by one-liners of the form:
A flash file system is a file system designed for storing files on flash memory–based storage devices. While flash file systems are closely related to file systems in general, they are optimized for the nature and characteristics of flash memory, and for use in particular operating systems.
The Linux kernel is a free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally authored in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU operating system, which was written to be a free (libre) replacement for Unix.
I/O Acceleration Technology (I/OAT) is a DMA engine by Intel bundled with high-end server motherboards, that offloads memory copies from the main processor by performing direct memory accesses (DMA). It is typically used for accelerating network traffic, but supports any kind of copy.
In computing, klibc is a minimalistic subset of the standard C library developed by H. Peter Anvin. It was developed mainly to be used during the Linux startup process, and it is part of the early user space, i.e. components used during kernel startup, but which do not run in kernel mode. These components do not have access to the standard library used by normal userspace programs.
cgroups is a Linux kernel feature that limits, accounts for, and isolates the resource usage of a collection of processes.
Supervisor Mode Access Prevention (SMAP) is a feature of some CPU implementations such as the Intel Broadwell microarchitecture that allows supervisor mode programs to optionally set user-space memory mappings so that access to those mappings from supervisor mode will cause a trap. This makes it harder for malicious programs to "trick" the kernel into using instructions or data from a user-space program.
zswap is a Linux kernel feature that provides a compressed write-back cache for swapped pages, as a form of virtual memory compression. Instead of moving memory pages to a swap device when they are to be swapped out, zswap performs their compression and then stores them into a memory pool dynamically allocated in the system RAM. Later writeback to the actual swap device is deferred or even completely avoided, resulting in a significantly reduced I/O for Linux systems that require swapping; the tradeoff is the need for additional CPU cycles to perform the compression.
Solid-state storage (SSS) is a type of non-volatile computer storage that stores and retrieves digital information using only electronic circuits, without any involvement of moving mechanical parts. This differs fundamentally from the traditional electromechanical storage, which records data using rotating or linearly moving media coated with magnetic material.
kpatch is a feature of the Linux kernel that implements live patching of a running kernel, which allows kernel patches to be applied while the kernel is still running. By avoiding the need for rebooting the system with a new kernel that contains the desired patches, kpatch aims to maximize the system uptime and availability. At the same time, kpatch allows kernel-related security updates to be applied without deferring them to scheduled downtimes. Internally, kpatch allows entire functions in a running kernel to be replaced with their patched versions, doing that safely by stopping all running processes while the live patching is performed.
In computing, OverlayFS is a union mount filesystem implementation for Linux. It combines multiple different underlying mount points into one, resulting in single directory structure that contains underlying files and sub-directories from all sources. Common applications overlay a read/write partition over a read-only partition, such as with LiveCDs and IoT devices with limited flash memory write cycles.
In computing, unique set size (USS) is the portion of main memory (RAM) occupied by a process which is guaranteed to be private to that process. The unshared memory of a process is reported as USS.
Kernel page-table isolation is a Linux kernel feature that mitigates the Meltdown security vulnerability and improves kernel hardening against attempts to bypass kernel address space layout randomization (KASLR). It works by better isolating user space and kernel space memory. KPTI was merged into Linux kernel version 4.15, and backported to Linux kernels 4.14.11, 4.9.75, and 4.4.110. Windows and macOS released similar updates. KPTI does not address the related Spectre vulnerability.
References
- ↑ "Understanding Resident Set Size and the RSS problem on modern Unixes". utcc.utoronto.ca. February 3, 2012. Retrieved January 22, 2015.
