Questions tagged [performance-tuning]
Performance tuning is the process of modifying a system to improve its efficiency. This is also known as optimizing.
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FreeBSD performance tuning: Sysctl parameter, loader.conf, kernel
I wanted to share knowledge of tuning FreeBSD via sysctl.conf / loader.conf
/ KENCONF / etc. It was initially based on Igor Sysoev's (author of nginx)
presentation about FreeBSD tuning up to 100,000-...
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2
answers
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Why is my bare-metal 16x 2.93GHz cores computer performing poorer than a VPS with 4x 2.5GHz cores?
I have a written a piece of multi-threaded software that does a bunch of simulations a day. This is a very CPU-intensive task, and I have been running this program on cloud services, usually on ...
30
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7
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Is it OK to run perfmon on production servers? And why?
Or should perfmon be limited to a Dev/QA server with load tests that simulate production activity?
I'd like to run perfmon for two days (like Sql Server master Brent Ozar suggests) to get an overall ...
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3
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Linux - real-world hardware RAID controller tuning (scsi and cciss)
Most of the Linux systems I manage feature hardware RAID controllers (mostly HP Smart Array). They're all running RHEL or CentOS.
I'm looking for real-world tunables to help optimize performance for ...
24
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How do I tell how close I'm getting to somaxconn?
The sysctl option net.core.somaxconn defaults to 128 (on our systems) but can be raised.
What exactly is this limit measuring and capping?
How do I find out how close I am to the limit?
Context: I ...
20
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7
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yslow says etags are misconfigured. how to configure etags properly on IIS7?
running ySlow on a website I support, I noticed it reported that the etags are misconfigured for the site images (e.g. *.jpg, *.png, *.gif). Can anyone help explain what I have to do to get IIS7 ...
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2
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Tuning (and understanding) table_cache in mySQL
I ran the excellent MySQL performance tuning script and started to work through the suggestions. One I ran into was
TABLE CACHE
Current table_cache value = 4096 tables You have a total
of 1073 ...
18
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2
answers
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How To Tune Apache on Ubuntu 14.04 Server
Currently on my Apache 2 (Apache 2.4.7 to be exact) on Ubuntu 14.04, I have this setting:
/etc/apache2/mods-enabled/mpm_prefork.conf
<IfModule mpm_prefork_module>
StartServers ...
18
votes
9
answers
69k
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Apache Tomcat chokes after 300 connections
We have an apache webserver in front of Tomcat hosted on EC2, instance type is extra large with 34GB memory.
Our application deals with lot of external webservices and we have a very lousy external ...
18
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3
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Building a 1,000M row MySQL table
This question is reposted from Stack Overflow based on a suggestion in the comments, apologies for the duplication.
Questions
Question 1: as the size of the database table gets larger how can I tune ...
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Should we mount with data=writeback and barrier=0 on ext3?
We've been running a server on a VM at a hosting company, and have just signed up for a dedicated host (AMD Opteron 3250, 4 cores, 8GB RAM, 2 x 1TB in software RAID, ext3).
While running performance ...
15
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5
answers
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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-- --...
14
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3
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Virtual machines and I/O heavy workload, is it ever sane?
I have seen on numerous virtualization services (Azure) and products (vmware,kvm,hyperv) I/O and system stalls under heavy I/O workload.
My questions are:
Is it ever sane to use a Virtualized ...
14
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2
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Low latency TCP settings on Ubuntu
There is a server for measurements running on Ubuntu in my lab. And there is C program, which receives data through TCP connection and should as soon as possible send a reply.
Configuration
CPUs: 2 ...
13
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4
answers
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Improving OpenVPN Performance
I've been trying to improve my OpenVPN performance and this is my current setup:
cat /etc/openvpn/server.conf
port 443 #- port
proto tcp #- protocol
dev tun
#tun-mtu 1500
tun-mtu-extra 32
#mssfix ...
13
votes
1
answer
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Virtualization - Ten 1Gbps links or one 10Gbps link? (Performance)
I have a machine that has several VM's (5) and 3 physical networking cards (with each 2 ports), with a total of six 1Gbps ethernet ports.
I have a SPF-capable switch, having a total of 48Gbps ...
13
votes
3
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How dangerous might it be - and what performance gains may be had - by turning vulnerability mitigations off on non-Internet facing servers?
When a virtual machine Linux host server is non-Internet facing and is used exclusively on a LAN and is using a relatively well tested distribution like Proxmox, how dangerous would it be to turn off ...
13
votes
5
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Performance Tuning a High-Load Apache Server
I am looking to understand some server performance problems I am seeing with a (for us) heavily loaded web server. The environment is as follows:
Debian Lenny (all stable packages + patched to ...
12
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13
answers
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Postfix performance
Running postfix on ubuntu, sending alot of mail ( ~ 1 million messages ) per day. loads are extremly high but not much in terms of cpu and memory load. Anyone in a similiar situation and know how to ...
12
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3
answers
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CPU0 is swamped with eth1 interrupts
I've got an Ubuntu VM, running inside Ubuntu-based Xen XCP. It hosts a custom FCGI-based HTTP service, behind nginx.
Under load from ab the first CPU core is saturated, and the rest is under-loaded.
...
12
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3
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Interpreting ethtool Coalesce output
Other than tx and rx being the transmit and recieve, can anyone explain what the fields mean in ethtool -c's (Coalescing output) and what effect they have on how coalescing works?
Coalesce parameters ...
11
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5
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How to measure req/sec by analyzing apache logs
I want to measure the justify stress-test result on production env.
How to measure req/sec by analyzing apache logs?
apache2.2
LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{...
11
votes
1
answer
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difference between taskset and cpuset
I'm trying to reduce the latency of my linux network application. I've learned that there are two tools for "binding" a program to particular CPU core: taskset and cpuset.
Which one should I prefer? ...
11
votes
3
answers
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Too much I/O generated by postgres stats collector process
I am using XenServer with several virtual machines having local postgres databases. Even when all applications are unused and the databases are idle, each vm causes constant storage network traffic ...
10
votes
6
answers
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Configuring NTFS file system for performance
We have an application that is planning to store around 1.1TB of XML files which average 8.5kb in size.
These represent a rolling 18 months of data, with around 200,000 new files being created every ...
10
votes
6
answers
4k
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Options for performance improvements on very big Filesystems and high IOWAIT
I have a Ubuntu 16.04 Backup Server with 8x10TB HDD via a SATA 3.0 Backplane. The 8 Harddisks are assembled to a RAID6, an EXT4 Filesystem is in use. This Filesystem stores a huge amount of small ...
10
votes
2
answers
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What are the implications of the SHOWPLAN permission on SQL Server 2005?
A user wants the SHOWPLAN permission in order to use Execution Plans to tune a query.
What are the implications of this permission. Is it safe to grant a user? I've seen the security note here, and ...
9
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4
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How to achieve 500K requests per second on my webserver? [closed]
I recently gifted myself a new dedicated server and I am trying to squeeze maximum performance out of it, for fun and learning.
I am trying to achieve maximum possible requests per second this server ...
9
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3
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What are your tricks for optimizing your Subversion configuration?
For a Linux or Windows system, what tricks do you do to optimize your Subversion server?
The following are my current tricks for a Linux system serving over Apache with HTTPS and backed by Active ...
9
votes
1
answer
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Best sysctl.conf configuration for high load - extremely busy content streaming server
What is the best sysctl.conf configuration for a high load, extremely busy content streaming server ?
The server fetches the content from remote servers like amazon, s3, etc. then uses php to ...
8
votes
3
answers
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Understanding RedHat's recommended tuned profiles
We are going to roll out tuned (and numad) on ~1000 servers, the majority of them being VMware servers either on NetApp or 3Par storage.
According to RedHats documentation we should choose the ...
8
votes
1
answer
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What do users see when Apache reaches MaxClients?
Occasionally, in my Apache error log, I will find:
[error] server reached MaxClients setting, consider raising the MaxClients setting
I've purposely lowered MaxClients in the past (to 60) due to ...
8
votes
2
answers
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How to raise max no of file descriptors for daemons running on Debian Jessie?
I'm playing with pgBouncer as a connection pooling system for PostgreSQL. My system is a 12-core with 64GB RAM and 1Gbps network interface running Debian 8.1. Now I want to raise the limit for open ...
8
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5
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Windows 7 network performance tuning for LAN
I want to tune Windows 7 TCP stack for speed in a LAN environment.
Bit of background info: I've got a Citrix XenServer set up with Windows 2008R2, Windows 7 and Debian Lenny with Citrix kernel, ...
8
votes
1
answer
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Why change net.inet.tcp.tcbhashsize in FreeBSD?
In virtually every FreeBSD network tuning document I can find:
# /boot/loader.conf
net.inet.tcp.tcbhashsize=4096
This is usually paired with some unhelpful statement like "TCP control-block hash ...
8
votes
2
answers
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what is the IOPS behavior when partitions of single disk are used in an LVM?
I have an ubuntu 14.04.1 LTS server which have LVM(backed by hardware RAID5) with logical volume and a volume group named "dbstore-lv" and "dbstore-vg" which have sdb1 sdb2 sdb3 created from same sdb ...
7
votes
2
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Ansible performance issues on a huge group
So, I have this host group, which consist of 35k VMs.
Aaaand I need to run a playbook over it.
If it does matter - playbook is just a call for community role for installing node_exporter.
But I'm ...
7
votes
2
answers
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Will noatime on a tmpfs volume improve performance?
I am using /run/shm/myfolder for nginx micro caching, also keeping ngx_pagespeed files there. I am wondering if there will be a speed increase if I go from relatime to noatime? It's for HDD, but on a ...
7
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2
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Faster IMAP searching for Courier IMAP server on Linux
I am looking for tips on improving IMAP search performance using Courier IMAP. The current version is 4.2.1. Unlike in the question "Fast search for IMAP?", I'm specifically looking for server side ...
7
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2
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Linux RAID-0 performance doesn't scale up over 1 GB/s
I have trouble getting the max throughput out of my setup. The hardware is as follow :
dual Quad-Core AMD Opteron(tm) Processor 2376
16 GB DDR2 ECC RAM
dual Adaptec 52245 RAID controllers
48 1 TB ...
7
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2
answers
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Does 'tuned' need to keep running?
On my CentOS 7 systems, I use tuned-adm to set a profile appropriate to the environment during configuration, but after that, I never subsequently change that profile. It seems that the tuned system ...
7
votes
1
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How long is the "defined grace period" for the idle scheduling class of the CFQ io scheduler?
The ionice man page says
A program running with idle io priority will only get disk time
when no other program has asked for disk io for a defined grace period.
Where is this "grace period" ...
7
votes
1
answer
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What is the best TCP congest algorithm to use for a mobile device?
Given the multitude of TCP algorithms available now and the rise of Linux based mobile devices, what are ideal algorithm(s) to consider?
From reading of the various implementations, Veno and Westwood+...
7
votes
3
answers
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Unexplained periodic humps in system CPU usage on W2K3E
We have a Windows 2003 R2 Enterprise 64-bit server running a custom workload suffering from an odd performance problem. The pared-down version below suffers from a smaller hump, but it's qualitatively ...
7
votes
3
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NetBackup Multiplexing for Oracle RMAN Backups
My question is... what multiplexing factor in NetBackup is recommended / do you use for Oracle RMAN backups over 1Gb/s management network to LTO3?
JB
Background:
With enterprise backup tools like ...
7
votes
3
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What does sunit=0 and swidth=0 mean for XFS file system?
I created an XFS file system using default parameters at the time of creation of a system. Now looking at the output of xfs_info, it show 0 for the values of sunit and swidth. I can't seem to find ...
6
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7
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Linux tool/command to check file system performance
What is the simplest way to check read/write performance to a specific location (e.g. a mounted iSCSI device).
I suspect I can't use hdparm because that's lower level. Am I right?
6
votes
8
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Hard Drive Speed: RPM vs. Cache
When trying to choose a SATA magnetic hard drive (not SSD) for high performance for both random and linear access, which should be the primary factor?
For example: would a 10k RPM drive with 16MB ...
6
votes
1
answer
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Lot of FIN_WAIT2, CLOSE_WAIT , LAST_ACK and TIME_WAIT in Haproxy
We are running haproxy in production for around 10k+ concurrent users. But we are seeing lot of FIN_WAIT2, CLOSE_WAIT , LAST_ACK and TIME_WAIT in the netstat output. This output is on a 8G ubuntu-12....
6
votes
1
answer
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How to prevent IO Load under Linux for Video serving?
I'm currently serving videos of conferences via Nginx on 3 servers; 4 cores, enough memory (no swap used) and RAID-10 with 8 drives per server. Unfortunately iostat -xd 1 gives me 100% on all 3 ...