Questions tagged [kernel]

In computing, the kernel is the main component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources (the communication between hardware and software components).

In computing, the kernel is the main component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources (the communication between hardware and software components).

Usually as a basic component of an operating system, a kernel can provide the lowest-level abstraction layer for the resources (especially processors and I/O devices) that application software must control to perform its function. It typically makes these facilities available to application processes through inter-process communication mechanisms and system calls.

Operating system tasks are done differently by different kernels, depending on their design and implementation. While monolithic kernels execute all the operating system code in the same address space to increase the performance of the system, microkernels run most of the operating system services in user space as servers, aiming to improve maintainability and modularity of the operating system.

Source: wikipedia

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In CentOS 6.x, how can I upgrade to Kernel 3.4?

I have a server running CentOS 6.2 with kernel version 2.6.32, but I need to increase my application Performance. The Kernel Version 3.4 has x32abi which can improve the performance so i want to upgrade to 3.4 ? Is it possible? I tried downloading…
shiva
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Find out which task is generating a lot of context switches on linux

According to vmstat, my Linux server (2xCore2 Duo 2.5 GHz) is constantly doing around 20k context switches per second. # vmstat 3 procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si…
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How does CPU affinity interact with cgroups in Linux?

I'm trying to run multi-threaded benchmarks on a set of isolated CPUs. To cut a long story short, I initially tried with isolcpus and taskset, but hit problems. Now I'm playing with cgroups/csets. I think the "simple" cset shield use-case should…
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systemd Using 4GB RAM After 18 Days of Uptime

I have a web server running CentOS 7, on which the systemd process is using nearly 4 GB of RAM after a couple weeks of uptime. RAM usage is increasing steadily at about 200MB per day. This and related processes like systemd-logind and dbus-daemon…
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How do you check the version of a *.ko kernel module in Linux?

I know you can do: sudo modprobe -v some_module to check the version of /lib/modules/.../some_module.ko, but I'd still like to be able to check the version of any arbitrary kernel module that's not necessarily going to be loaded by modprobe.
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How much does FreeBSD accept_filter actually improve performance in a modern world?

I recently learned about FreeBSD's accept_filter socket option which can allow a worker process to avoid context switching by, for example, waiting until a full HTTP request is received with accf_http: This is a filter to be placed on a socket…
Josh
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Strange: why does linux respond to ping with ARP request after last ping reply?

I (and a colleague) have just noticed, and tested, that when a Linux machine is pinged, after the last ping it initiates a unicast ARP request to the machine that initiated the ICMP ping. When pinging to a Windows machine, the Windows machine does…
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How to remove old kernels on CentOS 6 (to free up boot partition)?

How does one determine which kernels to remove in order to free up some space on /boot partition. Here is a scenario (some background info). 1. Parititon info (in case it helps) # df -h Filesystem Size Used Avail Use% Mounted on ... /dev/sda1 …
Shef
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How to set shmall, shmmax, shmmin, etc ... in general and for postgresql

I've used the documentation from PostgreSQL to set it for example this config: >>> cat /proc/meminfo MemTotal: 16345480 kB MemFree: 1770128 kB Buffers: 382184 kB Cached: 10432632 kB SwapCached: 0 kB Active:…
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How long does it take to fsck a volume?

We are running a website which is currently serving 3-5 million page views. Our site is a file sharing site and so it contains 250,000 files and few thousand symbolic links. The hard disk is a 1500GB SATA disk. Using hdparm we came to know that our…
khizar ansari
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What is creating the generated/autoconf.h?

We're trying to build a piece of software that demands the kernel source, not just the headers. So we downloaded the kernel source via the centos src rpm. However the autoconf.h is missing. We tried Put the .config in place (copied the one from…
Stefan
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How to fine tune TCP performance on Linux with a 10Gb fiber connection

We have 2 Red Hat servers that are dedicated for customer speedtest. They both use 10Gb fiber connections and sit on 10Gb links. All network gear in between these servers fully support 10Gb/s. Using Iperf or Iperf3 the best I can get is around…
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grubby fatal error: unable to find a suitable template

I'm trying to fix my system after moving it from one server to another. It works perfectly with kernel booted via network, but not from the disk. Reinstalling stock CentOS 6.6 kernel shows this error: grubby fatal error: unable to find a suitable…
Marek Zakrzewski
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Kernel: Uhhuh. NMI received for unknown reason 31 on CPU 3

I'm receiving this error on "Linux Debian-70-wheezy-64-minimal 3.2.0-4-amd64 #1 SMP Debian 3.2.46-1+deb7u1 x86_64": Message from syslogd@hostname at Feb 14 02:54:51 ... kernel:[81927.464687] Uhhuh. NMI received for unknown reason 31 on CPU…
user209395
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Why "lsmod | wc -l" not equal "ls /sys/module | wc -l"

Why do these two commands return different results? lsmod | wc -l 100 ls /sys/module | wc -l 138
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