服務器的負載能力，很大程度上取決於系統管理員的配置和優化能力。相同的硬件、不同的軟件配置，會造成截然不同的效果。下面我將給大家介紹一下如何優化 sysctrl, Apache 以及 mysql 。請注意，所有配置均為取決於個人，請根據自己的實際情況做調整。 配置Sysctl 編輯此文件： nano -w /etc/sysctl.conf 如果該文件為空，則輸入以下內容，否則請根據情況自己做調整： # Controls source route verification # Default should work for all interfaces net.ipv4.conf.default.rp_filter = 1 # net.ipv4.conf.all.rp_filter = 1 # net.ipv4.conf.lo.rp_filter = 1 # net.ipv4.conf.eth0.rp_filter = 1 # Disables IP source routing # Default should work for all interfaces net.ipv4.conf.default.accept_source_route = 0 # net.ipv4.conf.all.accept_source_route = 0 # net.ipv4.conf.lo.accept_source_route = 0 # net.ipv4.conf.eth0.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 # Increase maximum amount of memory allocated to shm # Only uncomment if needed! # kernel.shmmax = 67108864 # Disable ICMP Redirect Acceptance # Default should work for all interfaces net.ipv4.conf.default.accept_redirects = 0 # net.ipv4.conf.all.accept_redirects = 0 # net.ipv4.conf.lo.accept_redirects = 0 # net.ipv4.conf.eth0.accept_redirects = 0 # Enable Log Spoofed Packets, Source Routed Packets, Redirect Packets # Default should work for all interfaces net.ipv4.conf.default.log_martians = 1 # net.ipv4.conf.all.log_martians = 1 # net.ipv4.conf.lo.log_martians = 1 # net.ipv4.conf.eth0.log_martians = 1 # Decrease the time default value for tcp_fin_timeout connection net.ipv4.tcp_fin_timeout = 25 # Decrease the time default value for tcp_keepalive_time connection net.ipv4.tcp_keepalive_time = 1200 # Turn on the tcp_window_scaling net.ipv4.tcp_window_scaling = 1 # Turn on the tcp_sack net.ipv4.tcp_sack = 1 # tcp_fack should be on because of sack net.ipv4.tcp_fack = 1 # Turn on the tcp_timestamps net.ipv4.tcp_timestamps = 1 # Enable TCP SYN Cookie Protection net.ipv4.tcp_syncookies = 1 # Enable ignoring broadcasts request net.ipv4.icmp_echo_ignore_broadcasts = 1 # Enable bad error message Protection net.ipv4.icmp_ignore_bogus_error_responses = 1 # Make more local ports available # net.ipv4.ip_local_port_range = 1024 65000 # Set TCP Re-Ordering value in kernel to ‘5′ net.ipv4.tcp_reordering = 5 # Lower syn retry rates net.ipv4.tcp_synack_retries = 2 net.ipv4.tcp_syn_retries = 3 # Set Max SYN Backlog to ‘2048′ net.ipv4.tcp_max_syn_backlog = 2048 # Various Settings net.core.netdev_max_backlog = 1024 # Increase the maximum number of skb-heads to be cached net.core.hot_list_length = 256 # Increase the tcp-time-wait bUCkets pool size net.ipv4.tcp_max_tw_buckets = 360000 # This will increase the amount of memory available for socket input/output queues net.core.rmem_default = 65535 net.core.rmem_max = 8388608 net.ipv4.tcp_rmem = 4096 87380 8388608 net.core.wmem_default = 65535 net.core.wmem_max = 8388608 net.ipv4.tcp_wmem = 4096 65535 8388608 net.ipv4.tcp_mem = 8388608 8388608 8388608 net.core.optmem_max = 40960 如果希望屏蔽別人 ping 你的主機，則加入以下代碼： # Disable ping requests net.ipv4.icmp_echo_ignore_all = 1 編輯完成後，請執行以下命令使變動立即生效： /sbin/sysctl -p /sbin/sysctl -w net.ipv4.route.flush=1 MySQL優化 編輯MySQL的配置文件： nano /etc/my.cnf 輸入以下內容： [mysqld] connect_timeout=15 interactive_timeout=100 join_buffer_size=1M key_buffer=128M max_allowed_packet=16M max_connections=500 max_connect_errors=10 myisam_sort_buffer_size=64M read_buffer_size=1M read_rnd_buffer_size=768K sort_buffer_size=1M table_cache=1024 thread_cache_size=100 thread_concurrency=4 wait_timeout=300 query_cache_size=32M query_cache_limit=1M query_cache_type=1 skip-innodb 請注意，以上配置適用於512M~1024M內存，如內存更大的話請自行做調整。給項目增加內存會加快速度，但是使用過多的內存而導致啟用swap的話，會極大的導致系統效率下降。其中 thread_concurrency 這項配置，單CPU的話請設置為2，雙CPU的話請設置為4。 Apache優化 以下優化適用於 Apache 1.3 系列，如果你用的是 2.0 系列的話，請自行做調整和判斷。 確認 Apache 的配置文件位置並開始編輯： locate httpd.conf nano -w /path/to/httpd.conf httpd.conf的文件有許多內容，筆者就拿出需要做優化的： KeepAlive On MaxKeepAliveRequests 1000 KeepAliveTimeout 3 MinSpareServers 8 MaxSpareServers 13 MaxRequestsPerChild 50 將 KeepAliveTimeout 設定到較小的數字將有助於減少服務器上的無用等待鏈接，一定程度上能增加服務器負載。 另外，下面這條不算優化，但是是Apache安全相關： ServerSignature Off ServerTokens ProductOnly 將 ServerSignature 關閉，並增加 ServerTokens ProductOnly 可以使常人無法檢測到Apache的實際版本號，有助於Apache的安全。 以上所做的這些優化在某種程度上會增強服務器的負載性能。但請注意，最佳的配置是實踐出來的。
