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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133 votes
4 answers
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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-...
34 votes
2 answers
4k views

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 ...
Glauco Cattalini Lins's user avatar
30 votes
7 answers
19k views

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 ...
Bill Paetzke's user avatar
29 votes
3 answers
19k views

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 ...
ewwhite's user avatar
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24 votes
1 answer
15k views

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 ...
Andrew's user avatar
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20 votes
7 answers
38k views

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 ...
MikeJ's user avatar
  • 1,381
19 votes
2 answers
71k views

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 ...
jotango's user avatar
  • 475
18 votes
2 answers
68k views

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 ...
ServerChecker's user avatar
18 votes
9 answers
69k views

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 ...
john titus's user avatar
18 votes
3 answers
9k views

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 ...
Ben's user avatar
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15 votes
2 answers
21k views

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 ...
NeilB's user avatar
  • 253
15 votes
5 answers
56k views

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-- --...
grzaks's user avatar
  • 335
14 votes
3 answers
2k views

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 ...
bryan hunt's user avatar
14 votes
2 answers
40k views

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 ...
Alex V's user avatar
  • 143
13 votes
4 answers
84k views

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 ...
user avatar
13 votes
1 answer
2k views

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 ...
Gizmo's user avatar
  • 289
13 votes
3 answers
6k views

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 ...
ylluminate's user avatar
  • 1,197
13 votes
5 answers
15k views

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 ...
futureal's user avatar
  • 397
12 votes
13 answers
13k views

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 ...
Brian G's user avatar
  • 375
12 votes
3 answers
17k views

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. ...
Alexander Gladysh's user avatar
12 votes
3 answers
20k views

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 ...
Kyle Brandt's user avatar
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11 votes
5 answers
21k views

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\" \"%{...
freddiefujiwra's user avatar
11 votes
1 answer
11k views

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? ...
John Linberg's user avatar
11 votes
3 answers
7k views

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 ...
nn4l's user avatar
  • 1,336
10 votes
6 answers
15k views

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 ...
Richard Ev's user avatar
10 votes
6 answers
4k views

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 ...
t2m's user avatar
  • 136
10 votes
2 answers
8k views

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 ...
Josh's user avatar
  • 245
9 votes
4 answers
77k views

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 ...
Arpit Tambi's user avatar
9 votes
3 answers
7k views

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 ...
Scott Markwell's user avatar
9 votes
1 answer
9k views

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 ...
Daniel Johnson's user avatar
8 votes
3 answers
19k views

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 ...
espenfjo's user avatar
  • 1,686
8 votes
1 answer
2k views

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 ...
runningonplants's user avatar
8 votes
2 answers
15k views

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 ...
LBC's user avatar
  • 191
8 votes
5 answers
10k views

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, ...
Hubert Kario's user avatar
  • 6,401
8 votes
1 answer
2k views

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 ...
sh-beta's user avatar
  • 6,858
8 votes
2 answers
1k views

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 ...
sherpaurgen's user avatar
7 votes
2 answers
359 views

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 ...
Anatolii Tk's user avatar
7 votes
2 answers
3k views

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 ...
cenk's user avatar
  • 173
7 votes
2 answers
7k views

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 ...
Wade's user avatar
  • 173
7 votes
2 answers
2k views

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 ...
wazoox's user avatar
  • 6,998
7 votes
2 answers
23k views

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 ...
mhucka's user avatar
  • 699
7 votes
1 answer
1k views

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" ...
jhfrontz's user avatar
  • 293
7 votes
1 answer
11k views

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+...
cbc's user avatar
  • 121
7 votes
3 answers
601 views

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 ...
MikeyB's user avatar
  • 39.7k
7 votes
3 answers
4k views

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 ...
Jonathan Bourke's user avatar
7 votes
3 answers
5k views

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 ...
mhucka's user avatar
  • 699
6 votes
7 answers
11k views

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?
pufferfish's user avatar
  • 2,890
6 votes
8 answers
20k views

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 ...
Andrew Scagnelli's user avatar
6 votes
1 answer
18k views

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....
Tux's user avatar
  • 61
6 votes
1 answer
216 views

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 ...
CharlesS's user avatar
  • 228

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