Linux kernel performance optimization
– Kernel optimization starts —
\# Restart automatically after 1 second when kernel panic occurs
kernel.panic = 1\# Allows more PIDs (less rolled-out issues); may break some programs 32768
kernel.pid_max = 32768\# Maximum shared memory segment size allowed by the kernel (bytes)
kernel.shmmax = 4294967296\# Total amount of shared memory available on the system at any given time (pages)
kernel.shmall = 1073741824\# Set the file name format generated by the program core
kernel.core_pattern = core_%e\# Automatically converts to panic when oom occurs
vm.panic_on_oom = 1\# specifies the minimum amount of free memory that Linux VMS are forced to retain (Kbytes)
vm.min_free_kbytes = 1048576\# A value above 100 will cause the kernel to tend to reclaim the directory and inode cache
vm.vfs_cache_pressure = 250\# indicates the degree to which the system performs the switching behavior; the higher the value (0-100), the more likely a disk swap will occur
vm.swappiness = 20\# Use only 10% as system cache
vm.dirty_ratio = 10\# Added system file descriptor limit 2^20-1
fs.file-max = 1048575\# Network layer optimization
The default parameter for \# listen(), the maximum number of pending requests, defaults to 128
net.core.somaxconn = 1024\# Added Linux to automatically adjust TCP buffer limits
net.core.wmem\_default = 8388608
net.core.rmem\_default = 8388608
net.core.rmem\_max = 16777216
net.core.wmem\_max = 16777216\# Maximum device queue to enter a packet. The default is 300
net.core.netdev_max_backlog = 2000\# Enable SYN flood attack protection
net.ipv4.tcp_syncookies = 1\# Enable and log spoofing, source routing and redirection packets
net.ipv4.conf.all.log\_martians = 1
net.ipv4.conf.default.log\_martians = 1\# Processes packets that are passively routed
net.ipv4.conf.all.accept\_source\_route = 0
net.ipv4.conf.default.accept\_source\_route = 0\# Enable reverse path filtering
net.ipv4.conf.all.rp\_filter = 1
net.ipv4.conf.default.rp\_filter = 1\# Ensure that no one can modify the routing table
net.ipv4.conf.all.accept\_redirects = 0
net.ipv4.conf.default.accept\_redirects = 0
net.ipv4.conf.all.secure\_redirects = 0
net.ipv4.conf.default.secure\_redirects = 0\# Added system IP port limit
net.ipv4.ip_local_port_range = 9000 65533\# TTL
net.ipv4.ip_default_ttl = 64\# Increase the TCP maximum buffer size
net.ipv4.tcp\_rmem = 4096 87380 8388608
net.ipv4.tcp\_wmem = 4096 32768 8388608\# Tcp automatic window
net.ipv4.tcp_window_scaling = 1\# Enter the maximum request queue for SYN packets. The default is 1024
net.ipv4.tcp_max_syn_backlog = 8192\# Turn on time-wait socket reuse, which is very effective for Web servers with a large number of connections.
net.ipv4.tcp\_tw\_recycle = 1
net.ipv4.tcp\_tw\_reuse = 0 \# indicates whether to enable the calculation of RTT in a more precise way than timeout resend (see RFC 1323); This option should be enabled for better performance
net.ipv4.tcp_timestamps = 0\# Indicates the number of times a TCP SYN connection is timeout retransmitted
net.ipv4.tcp\_syn\_retries = 2
net.ipv4.tcp\_synack\_retries = 2\# Reduces the time spent in fin-waIT-2 connection state, allowing the system to handle more connections.
net.ipv4.tcp_fin_timeout = 10 # Reduce the time for TCP KeepAlive connection detection, allowing the system to handle more connections.
\# If a TCP connection is idle for 300 seconds, the kernel initiates a probe. If the probe fails two times (2 seconds each), the kernel gives up completely and considers the connection invalid.
net.ipv4.tcp\_keepalive\_time = 300
net.ipv4.tcp\_keepalive\_probes = 2
net.ipv4.tcp\_keepalive\_intvl = 2The maximum number of TCP Sockets that the system can handle that are not part of any process
net.ipv4.tcp_max_orphans = 262144\# The system also maintains a maximum number of TIME\_WAIT sockets. If this number is exceeded, the TIME\_WAIT socket is immediately cleared and a warning message is printed.
net.ipv4.tcp_max_tw_buckets = 20000 \# arp\_table cache limit optimized
net.ipv4.neigh.default.gc\_thresh1 = 128
net.ipv4.neigh.default.gc\_thresh2 = 512
net.ipv4.neigh.default.gc\_thresh3 = 4096— End of kernel optimization — —
For more information about Linux kernel parameters, see:
http://yangrong.blog.51cto.co…
