扬帆科技—专业的Linux服务器代维护

【重磅！】Linux下TCP优化脚本

作者：linux120 发布时间：March 14, 2014 分类：服务器配置

#!/bin/bash
host=$(hostname)

ARCH=$(uname -m)

which bc
if [ $? -ne 0 ]; then
echo "This script require GNU bc, cf. http://www.gnu.org/software/bc/"
echo "On Linux Debian/Ubuntu you can install it by doing : apt-get install bc"
fi

echo "Update sysctl for $host"

mem_bytes=$(awk '/MemTotal:/ { printf "%0.f",$2 * 1024}' /proc/meminfo)
shmmax=$(echo "$mem_bytes * 0.90" | bc | cut -f 1 -d '.')
shmall=$(expr $mem_bytes / $(getconf PAGE_SIZE))
max_orphan=$(echo "$mem_bytes * 0.10 / 65536" | bc | cut -f 1 -d '.')
file_max=$(echo "$mem_bytes / 4194304 * 256" | bc | cut -f 1 -d '.')
max_tw=$(($file_max*2))
min_free=$(echo "($mem_bytes / 1024) * 0.01" | bc | cut -f 1 -d '.')

if [ "$1" != "ssd" ]; then
vm_dirty_bg_ratio=5
vm_dirty_ratio=15
else
# This setup is generally ok for ssd and highmem servers
vm_dirty_bg_ratio=3
vm_dirty_ratio=5
fi

>/etc/sysctl.conf cat << EOF

# Disable syncookies (syncookies are not RFC compliant and can use too muche resources)
net.ipv4.tcp_syncookies = 0

# Basic TCP tuning
net.ipv4.tcp_keepalive_time = 600
net.ipv4.tcp_synack_retries = 3
net.ipv4.tcp_syn_retries = 3

# RFC1337
net.ipv4.tcp_rfc1337 = 1

# Defines the local port range that is used by TCP and UDP
# to choose the local port
net.ipv4.ip_local_port_range = 1024 65535

# Log packets with impossible addresses to kernel log
net.ipv4.conf.all.log_martians = 1

# Minimum interval between garbage collection passes This interval is
# in effect under high memory pressure on the pool
net.ipv4.inet_peer_gc_mintime = 5

# Disable Explicit Congestion Notification in TCP
net.ipv4.tcp_ecn = 0

# Enable window scaling as defined in RFC1323
net.ipv4.tcp_window_scaling = 1

# Enable timestamps (RFC1323)
net.ipv4.tcp_timestamps = 1

# Enable select acknowledgments
net.ipv4.tcp_sack = 1

# Enable FACK congestion avoidance and fast restransmission
net.ipv4.tcp_fack = 1

# Allows TCP to send "duplicate" SACKs
net.ipv4.tcp_dsack = 1

# Controls IP packet forwarding
net.ipv4.ip_forward = 0

# No controls source route verification (RFC1812)
net.ipv4.conf.default.rp_filter = 0

# Enable fast recycling TIME-WAIT sockets
net.ipv4.tcp_tw_recycle = 1

# TODO : change TCP_SYNQ_HSIZE in include/net/tcp.h
# to keep TCP_SYNQ_HSIZE*16<=tcp_max_syn_backlog
net.ipv4.tcp_max_syn_backlog = 20000

# tells the kernel how many TCP sockets that are not attached
# to any user file handle to maintain
net.ipv4.tcp_max_orphans = $max_orphan

# How may times to retry before killing TCP connection, closed by our side
net.ipv4.tcp_orphan_retries = 1

# how long to keep sockets in the state FIN-WAIT-2
# if we were the one closing the socket
net.ipv4.tcp_fin_timeout = 20

# maximum number of sockets in TIME-WAIT to be held simultaneously
net.ipv4.tcp_max_tw_buckets = $max_tw

# don't cache ssthresh from previous connection
net.ipv4.tcp_no_metrics_save = 1
net.ipv4.tcp_moderate_rcvbuf = 1

# increase Linux autotuning TCP buffer limits
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216

# increase TCP max buffer size
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216

net.core.netdev_max_backlog = 2500
net.core.somaxconn = 65000

vm.swappiness = 0

# You can monitor the kernel behavior with regard to the dirty
# pages by using grep -A 1 dirty /proc/vmstat
vm.dirty_background_ratio = $vm_dirty_bg_ratio
vm.dirty_ratio = $vm_dirty_ratio

# required free memory (set to 1% of physical ram)
vm.min_free_kbytes = $min_free

# system open file limit
fs.file-max = $file_max

# Core dump suidsafe
fs.suid_dumpable = 2

kernel.printk = 4 4 1 7
kernel.core_uses_pid = 1
kernel.sysrq = 0
kernel.msgmax = 65536
kernel.msgmnb = 65536

# Maximum shared segment size in bytes
kernel.shmmax = $shmmax

# Maximum number of shared memory segments in pages
kernel.shmall = $shmall
EOF

/sbin/sysctl -p /etc/sysctl.conf
exit $?

php编译提示 ac_fn_c_try_run 错误

作者：linux120 发布时间：March 6, 2014 分类：服务器配置

请再三检查autoconf版本，建议使用2.13
然后声明
export PHP_AUTOCONF=/usr/local/autoconf-2.13/bin/autoconf
export PHP_AUTOHEADER=/usr/local/autoconf-2.13/bin/autoheader

如何改进MySQL Order By Rand()

作者：linux120 发布时间：February 26, 2014 分类：服务器配置

mysql数据库的随机函数很消耗资源的，官方也不建议在order中使用rand()，客户在150w条的表里面进行查询15条，耗费1.5s，
SELECT * FROM items ORDER BY RAND() LIMIT 15
大量堵塞了mysql进程，下面分享一下我司dba给出的解决方案，使用该方案后随机查询15条数据耗费0.001s。不用谢。
$sql="SELECT MAX(id),MIN(id) FROM items ";
$result=mysql_query($sql,$conn);
$yi=mysql_fetch_array($result);
$idmax=$yi[0];
$idmin=$yi[1];
$idlist='';
for($i=1;$i<=20;$i++){
if($i==1){ $idlist=mt_rand($idmin,$idmax); }
else{ $idlist=$idlist.','.mt_rand($idmin,$idmax); }
}
$idlist2="id,".$idlist;
$sql="select * from items where id in ($idlist) order by field($idlist2) LIMIT 0,15";
$result=mysql_query($sql,$conn);
$n=1;
$rnds='';
while($row=mysql_fetch_array($result)){
$rnds=$rnds.$n.". ".$row['title']."
\n";
$n++;
}

mysql socket 冲突

作者：linux120 发布时间：February 13, 2014 分类：服务器配置

可能是由以下原因造成的。
1异常关闭， 来不及删除；
2已有一个mysql实例在正常运行；
3该磁盘分区文件系统损坏文件只读删不掉socket。

再分享一个优化过的生产环境nginx配置

作者：linux120 发布时间：November 21, 2013 分类：服务器配置

user www-data;
pid /var/run/nginx.pid;
worker_processes auto;
worker_rlimit_nofile 100000;

events {
worker_connections 2048;
multi_accept on;
use epoll;
}

http {
server_tokens off;
sendfile on;
tcp_nopush on;
tcp_nodelay on;

access_log off;
error_log /var/log/nginx/error.log crit;

keepalive_timeout 10;
client_header_timeout 10;
client_body_timeout 10;
reset_timedout_connection on;
send_timeout 10;

limit_conn_zone $binary_remote_addr zone=addr:5m;
limit_conn addr 100;

include /etc/nginx/mime.types;
default_type text/html;
charset UTF-8;

gzip on;
gzip_disable "msie6";
gzip_proxied any;
gzip_min_length 1000;
gzip_comp_level 6;
gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript;

open_file_cache max=100000 inactive=20s;
open_file_cache_valid 30s;
open_file_cache_min_uses 2;
open_file_cache_errors on;

include /etc/nginx/conf.d/*.conf;
include /etc/nginx/sites-enabled/*;
}