sysctl.conf at www.scaleout.jp

# Kernel sysctl configuration file for Red Hat Linux
#
# For binary values, 0 is disabled, 1 is enabled.  See sysctl(8) and
# sysctl.conf(5) for more details.

# Controls IP packet forwarding
net.ipv4.ip_forward = 0
# Controls source route verification
net.ipv4.conf.default.rp_filter = 0

# Do not accept source routing
net.ipv4.conf.default.accept_source_route = 0

# Controls the System Request debugging functionality of the kernel
kernel.sysrq = 0

# Controls whether core dumps will append the PID to the core filename
# Useful for debugging multi-threaded applications
kernel.core_uses_pid = 1

# Controls the use of TCP syncookies
net.ipv4.tcp_syncookies = 1

# Controls the maximum size of a message, in bytes
kernel.msgmnb = 65536

# Controls the default maxmimum size of a mesage queue
kernel.msgmax = 65536

# Controls the maximum shared segment size, in bytes
kernel.shmmax = 4294967295

# Controls the maximum number of shared memory segments, in pages
kernel.shmall = 268435456

#
# Tunning Over 4GB Server
#

# increase Linux autotuning TCP buffer limits
# min, default, and max number of bytes to use
# set max to 16MB for 1GE, and 32M or 54M for 10GE
net.ipv4.tcp_rmem = 4096 87380 8388608
net.ipv4.tcp_wmem = 4096 65536 6553600

# increase TCP max buffer size setable using setsockopt()
net.core.rmem_max = 8388608
net.core.wmem_max = 6553600

# recommended to increase this for 10G NICS
net.core.netdev_max_backlog = 5000

# How often TCP sends out keepalive messages when keepalive is enabled. Default: 2hours.
net.ipv4.tcp_keepalive_time = 1800

# This boolean enables a fix for 'time-wait assassination hazards in tcp', described in RFC 1337. If enabled, this causes the kernel to drop RST packets for sockets in the time-wait
net.ipv4.tcp_rfc1337 = 1

# Timestamps are used, amongst other things, to protect against wrapping sequence numbers. 
# A 1 gigabit link might conceivably re-encounter a previous sequence number with an out-of-line value, 
# because it was of a previous generation. The timestamp will let it recognize this 'ancient packet'.
net.ipv4.tcp_timestamps = 1

# Maximal number of remembered connection requests, 
# which still did not receive an acknowledgment from connecting client. 
# Default value is 1024 for systems with more than 128Mb of memory, 
# and 128 for low memory machines. If server suffers of overload, try to increase this number. 
# Warning! If you make it greater than 1024, 
# it would be better to change TCP_SYNQ_HSIZE in 
# include/net/tcp.h to keep TCP_SYNQ_HSIZE*16<=tcp_max_syn_backlog and to recompile kernel.
net.ipv4.tcp_max_syn_backlog = 10240

# Maximal number of timewait sockets held by system simultaneously.
# If this number is exceeded time-wait socket is immediately destroyed and warning is printed.
# This limit exists only to prevent simple DoS attacks,
# you _must_ not lower the limit artificially,
# but rather increase it (probably, after increasing installed memory),
# if network conditions require more than default value.
net.ipv4.tcp_max_tw_buckets = 1000000

# Range of local ports for outgoing connections. 
# Actually quite small by default, 1024 to 4999.
#port lange
net.ipv4.ip_local_port_range =  10240    61000

#TCP MSL
#
# Time to hold socket in state FIN-WAIT-2,
# if it was closed by our side. Peer can be broken and never close its side,
# or even died unexpectedly.
# Default value is 60sec. Usual value used in 2.2 was 180 seconds,
# you may restore it, but remember that if your machine is even underloaded WEB server,
# you risk to overflow memory with kilotons of dead sockets,
# FIN-WAIT-2 sockets are less dangerous than FIN-WAIT-1,
# because they eat maximum 1.5K of memory, but they tend to live longer.
# Cf. tcp_max_orphans.
net.ipv4.tcp_fin_timeout=30