The Linux kernel is the operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software.

learn more… | top users | synonyms

3
votes
1answer
71 views

how to determine who is using the slabs?

Is there any way to figure out who or what is allocating size-256 slabs, like in the slabtop output below? I had to reboot a server yesterday that had 5G out of 8G RAM in size-256 slabs and was ...
2
votes
1answer
352 views

/proc/<pid>/stat children CPU time

I've been running the following command on my linux box: watch -d -n 1 "cat /proc/19866/stat" The pid above is a pid of Nginx's master process - I would expect the following fields to be changing: ...
2
votes
1answer
212 views

best practice after upgrading the kernel

Greetings ... I need to know what anyone should do after upgrading the kernel ? How to do quick check if the kernel is suited for the server's softwares , check whether if kernel is compilable with ...
1
vote
1answer
107 views

Windows multicast NLB with Linux clients

I'm (on behalf of a client, anyway) having some troubles with Linux accessing a multicast NLB cluster hosted on Hyper-V (waiting for more information on what version, but I don't think the version is ...
1
vote
1answer
955 views

“show_signal_msg: N callbacks suppressed” then pegged at 100% and machine unresponsive

This happened on an Ubuntu 14.04 64-bit DigitalOcean Droplet: Apr 22 02:17:02 localhost CRON[32514]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly) Apr 22 03:16:59 localhost ...
1
vote
1answer
416 views

ArchLinux under Xen fails to see root fs after kernel upgrade to Linux-3.0

I bought a VPS but the hosting company doesn't have a prebuilt image for Arch Linux x64, so I have to install from ISO using VNC in SolusVM. The installation works fine, the box (Xen Guest) is ...
0
votes
1answer
31 views

IPSEC stack low speed

I am working on Openswan IPSEC Implementation for Linux-kernel 2.6.35.9 My concern is when i do speed test using IPSEC kernel Images and without running IPSEC service i get speed of 40Mbps and ...
2
votes
0answers
37 views

What are the advantages NAPI before the IRQ Coalesce?

As known there are two approach to avoid some overheads of hardware interrupts in highload networks, when there are too many hardware interrupts, that switching to them takes too much time. It is very ...
2
votes
0answers
67 views

“Nosy Neighbor” and the CFQ scheduler

I'm trying to understand how does using CFQ affects the "Nosy Neighbor" problem. I'll ask it a bit naively, can a "Nosy Neighbor" even exist when using CFQ? Isn't that CFQ should make sure all ...
2
votes
0answers
570 views

Should I set rto_min for a route inside data center?

We have a few dedicated server rented in a data center with debian 7, kernel 3.2. We use one of those servers as a database server. The network between our application server and database server is ...
2
votes
0answers
57 views

Sun Fire V40z, big gap between memory reported by dmidecode and what the Linux kernel sees

I'm looking after a V40z (a loaner), running RHEL 4.8 (no, I can't update it, it's a loaner) that according to dmidecode has 8 DIMMs of 2048M each, which makes for 16GB RAM as far as I'm concerned. ...
2
votes
0answers
497 views

netmap issue with wheezy linux kernel 3.2.0.4 and Intel Corporation 82599EB 10-Gigabit card

I have compiled the netmap drivers on debian wheezy with kernel 3.2.0.4 and ixgbe patched module from netmap drivers code. When I insert the modules after removing default ixgbe module I get the ...
2
votes
0answers
389 views

KVM host kernel configuration for best performance

I'm currently building a kernel for my server, which should serve for hosting virtual machines using KVM. There are a few kernel configuration options that are already described in the KVM-Wiki. The ...
1
vote
0answers
25 views

strace not showing anything for thread at 100% 'system' CPU

I'm having difficulty with my Python app going to 100% 'system' CPU time across multiple threads for up to 10+ seconds. My (limited) understanding is that 'system' CPU time is time spent in the ...
1
vote
0answers
34 views

Server crashes because of SMP

My web server is crashing every few days unless I disable SMP with "nosmp" parameter in Grub config. It is not an hardware failure because the problem persists after moving everything to a new ...
1
vote
0answers
101 views

“error: ‘PATH_MAX’ undeclared” when trying to make menuconfig

I have an OVH cloud VPS with Ubuntu 14.04 64 bit server. I needed linux headers which OVH does not provide by default, so I found some tutorials on how to compile the linux kernel from source using ...
1
vote
0answers
143 views

PCIe card memory regions ignored on linux kernel 3.13

On my system, with kernel 3.13.0-32-generic (Ubuntu Server 14.04.1 LTS) installed, one of the PCIe boards in the system (06:00.0) is having it's memory regions ignored: Interrupt: pin A routed to IRQ ...
1
vote
0answers
84 views

The default value for vm.dirty_background_ratio

Wondering why the default value for "vm.dirty_background_ratio" from Linux Server (CentOS and Ubuntu) is set to 40. Is this just a recommendation for safety? Or is there any particular reason why? ...
1
vote
0answers
91 views

linux not replying to an arp request

I am running linux 3.14 on a system with 2 interfaces. on the first interface, i can access our local network. on the second interface, arp packets come in but linux doesn't send out reply. is it ...
1
vote
0answers
114 views

task fstrim blocked for more than 120 seconds

I'm experiencing random crashes on my system. I've narrowed the problem to the fstrim program that's launched weekly by cron. In the console, I've got a set of blocked tasks among whigetch I find ...
1
vote
0answers
182 views

shorewall can'T start: UNTRACKED state requires Raw Table in your kernel and iptables

I'm trying setting up my firewall and installed and configured shorewall. Unfortunately I tried to directly configure iptables first, but this didn't work. When I start shorewall, I get this messages ...
1
vote
0answers
630 views

Linode Kernel Headers

I am trying to install the Idera (R1soft) linux agent on a Linode running Ubuntu 12.04LTS. The agent requires a driver which in turn requires the kernel headers. Linode uses custom kernels though so ...
1
vote
0answers
91 views

__ticket_spinlock high cpu

We are having a strange problem on our Ubuntu 10.04 KVM infrastructure, where periodically, one of two vm webservers freaks out, with persistently high load, even if we restart the applications. (the ...
1
vote
0answers
129 views

ext3 option on error doesn't work

I have a redhat server 5.8 with ext3 on top of lvm, i noticed ext3 has setting "Errors behavior: Continue" in the fs super block, from the man page of mount command i readed this ...
1
vote
0answers
180 views

Capturing on loopback device on Ubuntu LTS: 15 Mbit of traffic and “x dropped packets”

I am trying to capture about 15 Mbit of traffic on the loopback device on Ubuntu LTS using tcpdump, and I am seeing dropped packets. The CPU is a freaking i7, and i have yet to see CPU usage go above ...
1
vote
0answers
170 views

linux kernel configuration to filter multicast traffic based on interface

I have two virtual interfaces (eth0.2, eth0.3) in my PC. I am sending multicast data from eth0.2 to eth0.2. Multicast data is received in eth0.2 but also received in eth0.3, the other virtual ...
1
vote
0answers
203 views

Tracking huge buffer usage under Linux

I'v a Linux server running under Debian Lenny with 4Go of RAM. It doesn't run a large number of stuffs: Postfix/spamassassin (daemon mode) Bind9 KVM (one guest - 1Go of RAM for it) Every day at ...
1
vote
0answers
592 views

How to modify Ubuntu 10.04.1 Grub entry for supporting KGDB kernel image

I am trying to update target m/c grub.cfg file for KGDB setup but while booting the m/c it got hung completely and not asking/waiting for remote gdb connection. Following is the entry which I added:- ...
0
votes
0answers
7 views

Is transparent hugepage support on or off on these CoreOS machines?

I have a number of CoreOS servers that will be running some database workloads that highly recommend Transparent Hugepages be disabled. However: ~$ cat /sys/kernel/mm/transparent_hugepage/enabled ...
0
votes
0answers
19 views

Installing LTTng-modules 2.5.4 on CentOS 7

I am trying to install LTTng-modules 2.5.4 on CentOS 7, by building it from source because CentOS 7 is unable to install this package from RPM. Running "make" to build package contents results in the ...
0
votes
0answers
35 views

CPU usage of server extremely low and webpage load time high?

On a weekday at a time where very few use the optimized website on the server, the time for the page to completely load excluding 3rd party advertisements is about 0.6 seconds to 1 second. Now when a ...
0
votes
0answers
15 views

How to show per-process amount of non-swappable memory?

I am using a VPS which has, unfortunately, stringent limits on maximum total size of non-swappable memory for all processes in the container; this limit is called in kmemsize in OpenVZ. I would like ...
0
votes
0answers
72 views

Random machine hangs with NFSv4 on CentOS/RHEL 6.5

We have an in-house "compute farm" with about 100 CentOS (free re-distribution of RHEL) 5.7 and 6.5 x86_64 servers. (We are in the process of upgrading all the 5.7 boxes to 6.5.) All these machines ...
0
votes
0answers
24 views

strongSwan on Angstrom

My problem is to establish a VPN tunnel between cRIO 9068 and a Cisco router. To accomplish this task I was planning to install strongswan on cRIO (opkg install strongswan). I have installed it on ...
0
votes
0answers
40 views

linux system slab cache proc_node_cache usage too large

My system run java program only, at some time the memory usage increase very quickly to a very hight percentage: memory usage of java : PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ ...
0
votes
0answers
27 views

Purpose of sysctrl tcp timeout unack field

Could some one let me know the purpose of sysctrl tcp timeout unack? If i modify this value from 300 t0 400, what will be the impact. /proc/sys/net/netfilter/nf_conntrack_tcp_timeout_unacknowledged ...
0
votes
0answers
28 views

Can you use isolcpus or other kernel parameters in AWS?

We have recently started using cpuset for certain network intensive processes and I want to set a system-wide default for everything else so it doesn't use the designated cores. After a few seconds ...
0
votes
0answers
317 views

rcu_sched self-detected stall on CPU on Debian server

My server is online since October 2014. Debian GNU/Linux 7.6 uname -r 3.10.23-xxxx-std-ipv6-64 It was working fine till last night. Last night it bacame unresponsible. I rebooted it from dadata ...
0
votes
0answers
29 views

Analyse kernel crash file on Ubuntu server 11.10

I am experiencing random crashes on a Ubuntu 11.10 server, and for the time being the system can not be upgraded, even tho this distro is very old. uname -r 3.0.0-12-server I've set it up to get a ...
0
votes
0answers
45 views

Centos 7 cpu frequency below the minimum value

Hyeverybody,I have 2 similar Dell PowerEdge r720 server wih the following configuration: CPU: Intel(R) Xeon(R) CPU E5-2630 v2 @ 2.60GHz RAM: 64GB OS: Centos 7 I have noticed, that the in recent 2 ...
0
votes
0answers
87 views

Must kernel-version of Ubuntu linux-cloud-tools match the kernel version of linux vm on hyper-v?

Microsoft's recommendations for installing Ubuntu VM's on Hyper-V (note 5) include installing kernel-specific versions of the linux-tools and linux-cloud-tools packages. However, there are also two ...
0
votes
0answers
188 views

What are the pros and cons of large receive offload (LRO) vs generic receive offload (GRO)

I have been debugging a scenario where an ESX vmware host is communicating with a virtual linux machine via a virtual switch using TCP/IP. After a congestion event the vmware host is waiting for an ...
0
votes
0answers
83 views

Apache hanging - FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME

We are running Apache 2.2.15 on a CentOS 6.6 server [2.6.32-504.3.3.el6.x86_64] (with FastCGI PHP, mod_pagespeed, mod_spdy, etc) all the most recent versions. Today we had a case where on one of our ...
0
votes
0answers
78 views

INFO : task events/2:69 blocked for more than 120 seconds

I'm using RHEL 6.3 running on VMWare vsphere and aproximatively every month there is this error message and application running above hang until I restart the server: "echo 0 > ...
0
votes
0answers
126 views

Utility to list and modify kernel modules loaded during system startup

How do I list all kernel modules loaded while system startup? Is there a user space utility to list and modify the modules loaded during system startup? I am working on RHEL6 Desktop and RHEL6 ...
0
votes
0answers
69 views

systemrescuecd 4.3.1: parted cannot inform kernel of change

I am trying to use parted (3.2) on systemrescuecd (4.3.1), but keep getting the error message similar to below. Error: Partition(s) 2, 3, 4 on /dev/sdd have been written, but we have been unable to ...
0
votes
0answers
41 views

Upgrading to PAE Kernel

I have Fedora 15 running in a box with 8GB ram and a 32 bit kernel; I would like to make use of the entire RAM real estate by upgrading to a PAE Kernel; however the machine is in a remote location and ...
0
votes
0answers
141 views

zeroshell unsupported onboard Intel Ethernet I217-V and I210

I recently installed zeroshell 3.0.0 on a machine with a supermicro motherboard that has 2 onboard ethernet cards. It seems that this version of ZS does not support both of ethernet. I've read from ...
0
votes
0answers
97 views

Cassandra hangs with kernel exception when adding jna jar to classpath

I have a fresh installation of cassandra v2.0.8 on a RedHat Enterprise Linux v5. I have added a sym link of the jna.jar in cassandra's /lib folder. I start cassandra and it hangs after printing out ...
0
votes
0answers
582 views

Server crash : “unable to handle kernel paging request”

My fresh new Ubuntu webserver randomly crashes with the following error in the syslog. It doesn't respond anymore and I have to do a hard reboot. It happens almost one time a day. Server kernel is : ...