Shmall and Shmmax parameters of the kernelThe shmmax= is configured with the largest memory segment size------> This setting is much better than sga_max_size.
Shmmin= the smallest amount of memory segment
Shmmni= the total number of memory segment for the entire system
Shmseg= the maximum number of memory segment that can be used per process
Parameters for configuration Beacon (Semphore):
Semmsl= the number of Semphore per Semphore set-----> This setting is greater than the number of your process, otherwise you have to divide multiple semphore set, as if there were process+n, I forgot N is a few.
semmni= Total Semphore Set totals for the entire system
semmns= total number of Semphore for the entire system
Shmall is the total allowed shared memory size, Shmmax is the size allowed for a single segment. These two can be set to 90% of memory. For example 16G memory, 16*1024*1024*1024*90% = 15461882265,shmall size is 15461882265/4k (getconf pagesize available) = 3774873. Modify/etc/sysctl.conf
kernel.shmmax=15461882265
kernel.shmall=3774873
kernel.msgmax=65535
kernel.msgmnb=65535
Execute sudo sysctl-p
You can use Ipcs-l to see the results. Ipcs-u can see the actual use of the situation
========================================================================Linux Memory ManagementFirst, preface
This document is aimed at OOP8 production environment, the specific optimization strategy needs to be adjusted according to the actual situation, the following aspects will explain how to optimize performance for Redhat Enterprise Linux.
1) Linux proc file system, through the proc file system to adjust to achieve the purpose of performance optimization.
2) Linux Performance Diagnostic Tool, describes how to use the Linux-brought diagnostic tools for performance diagnosis.
Bold Italic represents a command that can be run directly.
The underscore indicates the contents of the file.
Second,/proc/sys/kernel/optimization
1)/proc/sys/kernel/ctrl-alt-del
The file has a binary value that controls how the system reacts when it receives the Ctrl+alt+delete key combination. The two values are:
A value of 0 (0) that captures the ctrl+alt+delete and sends it to the INIT program, which allows the system to be safely shut down and restarted as if the shutdown command was entered.
One (1) value, which means that the ctrl+alt+delete is not captured and will perform an abnormal shutdown, as if the power is turned off.
Default setting: 0
Recommended setting: 1 To prevent accidental press of ctrl+alt+delete causing abnormal system restart.
2) Proc/sys/kernel/msgmax
This file specifies the maximum length (bytes) of messages sent from one process to another. Inter-process messaging is done in the kernel's memory and is not swapped to disk, so increasing the value increases the amount of memory used by the operating system.
Default setting: 8192
3)/PROC/SYS/KERNEL/MSGMNB
The file specifies the maximum length of a message queue (bytes).
Default setting: 16384
4)/proc/sys/kernel/msgmni
This file specifies the maximum number of message queue identities, which is the maximum system-wide message queue.
Default setting: 16
5)/proc/sys/kernel/panic
This file indicates the time (in seconds) that the kernel waits before rebooting if "kernel Critical error (Kernel panic)" occurs.
0 (0) seconds, indicating that automatic reboots will be disabled if a kernel critical error occurs.
Default setting: 0
6) Proc/sys/kernel/shmall
This file represents the total amount of shared memory (bytes) that can be used on the system at any given moment.
Default setting: 2097152
7)/proc/sys/kernel/shmmax
This file represents the size of the maximum shared memory segment allowed by the kernel (bytes).
Default setting: 33554432
Recommended setting: Physical Memory * 50%
The actual available maximum shared memory segment size is =shmmax * 98%, of which approximately 2% is used for shared memory structures.
You can verify this by setting Shmmax, and then performing ipcs-l.
8)/proc/sys/kernel/shmmni
The file represents the maximum number of shared memory segments used for the entire system (each).
Default setting: 4096
9)/proc/sys/kernel/threads-max
This file represents the maximum number of threads that the kernel can use.
Default setting: 2048
)/proc/sys/kernel/sem
This file is used to control the kernel semaphore, which is the method used by system VIPC for interprocess communication.
Recommended setting: 250 32000 100 128
The first column, which represents the maximum number of semaphores in each signal set.
The second column, which represents the total number of maximum semaphores in the system range.
The third column, which represents the maximum number of system operations per signal occurrence.
The fourth column, which represents the maximum number of signal lumped in the system range.
So, (first column) * (fourth column) = (second column)
The above settings can be verified by executing ipcs-l.
11) to be continued ...
Third,/proc/sys/vm/optimization
1)/proc/sys/vm/block_dump
This file indicates whether block debug mode is turned on to record all read-write and dirty block writeback actions.
Default setting: 0, disable block debug mode
2)/proc/sys/vm/dirty_background_ratio
This file represents the percentage of dirty data that reaches the overall system memory, triggering the pdflush process to write dirty data back to disk.
Default setting: 10
3)/proc/sys/vm/dirty_expire_centisecs
The file indicates that if the dirty data resides in memory longer than this value, the Pdflush process will write the data back to disk the next time.
Default setting: 3000 (1/100 sec)
4)/proc/sys/vm/dirty_ratio
This file indicates that if the dirty data generated by the process reaches the percentage of the system's overall memory, the process itself writes the dirty data back to disk.
Default setting: 40
5)/proc/sys/vm/dirty_writeback_centisecs
This file indicates how often the Pdflush process writes dirty data back to disk.
Default setting: 500 (1/100 sec)
6)/proc/sys/vm/vfs_cache_pressure
This file indicates that the kernel recycles the memory used by the directory and Inode caches, and the default value of 100 means that the kernel will keep the directory and inode caches at a reasonable percentage based on Pagecache and Swapcache. Lowering this value below 100 causes the kernel to tend to retain the directory and Inode caches, and increasing this value by more than 100 will cause the kernel to tend to reclaim the directory and Inode caches.
Default setting: 100
7)/proc/sys/vm/min_free_kbytes
This file represents the minimum amount of free memory (Kbytes) that the Linux VM is forced to keep.
Default setting: 724 (512M physical memory)
8)/proc/sys/vm/nr_pdflush_threads
This file represents the number of Pdflush processes currently running, and the kernel will automatically add more Pdflush processes with high I/O load.
Default setting: 2 (Read only)
9)/proc/sys/vm/overcommit_memory
This file specifies the kernel's policy for memory allocation, which can be 0, 1, 2.
0, indicates that the kernel will check for sufficient available memory to be used by the process, and if sufficient memory is available, the memory request is allowed; otherwise, the memory request fails and the error is returned to the application process.
1, which means that the kernel allows all physical memory to be allocated regardless of the current memory state.
2, which indicates that the kernel allows allocating more memory than the sum of all physical memory and swap space (refer to Overcommit_ratio).
Default setting: 0
)/proc/sys/vm/overcommit_ratio
The file indicates that if overcommit_memory=2, the percentage of memory that can be overloaded, the overall available memory of the system is calculated by the following formula.
System assignable Memory = Swap space + physical memory *overcommit_ratio/100
Default setting: 50 (%)
One)/proc/sys/vm/page-cluster
This file represents the number of pages written once to the swap area, 0 for 1 pages, 1 for 2 pages, and 2 for 4 pages.
Default setting: 3 (2 of 3 parties, 8 pages)
/proc/sys/vm/swapiness)
The file represents the degree to which the system is exchanging behavior, and the higher the value (0-100), the more likely the disk exchange will occur.
Default setting: 60
Legacy_va_layout)
This file indicates whether to use the latest 32-bit shared memory mmap () system calls, and how Linux supports shared memory allocations including mmap (), Posix,system VIPC.
0, use the latest 32-bit mmap () system call.
1, use the system call provided by the 2.4 kernel.
Default setting: 0
Nr_hugepages)
The file represents the number of hugetlb pages reserved by the system.
Hugetlb_shm_group)
This file represents the System group ID that allows the hugetlb page to be used to create systems VIPC shared memory segments.
16) to be continued ...
Iv. optimization of/proc/sys/fs/
1)/proc/sys/fs/file-max
This file specifies the maximum number of file handles that can be allocated. If the user gets an error message that is declared due to open
The maximum number of files has been reached so that they cannot open more files, you may need to increase this value.
Default setting: 4096
Recommended setting: 65536
2)/proc/sys/fs/file-nr
This file is related to File-max and it has three values:
Number of allocated file handles
The number of file handles that have been used
Maximum number of file handles
The file is read-only and is used only to display information.
3) to be continued ...
Five,/proc/sys/net/core/optimization
The configuration file under this directory is primarily used to control the interaction between the kernel and the network layer.
1)/proc/sys/net/core/message_burst
The time, in 1/10 seconds, that is required to write a new warning message, and the other warning messages received by the system during this time are discarded. This is used to prevent some attempts to "overwhelm" the system with a denial of service (denial of services) attack.
Default setting: 50 (5 seconds)
2)/proc/sys/net/core/message_cost
The file represents the cost value that is related to writing each warning message. The larger the value, the more likely it is to ignore the warning message.
Default setting: 5
3)/proc/sys/net/core/netdev_max_backlog
The file represents the maximum number of packets that are allowed to be sent to the queue when each network interface receives a packet at a rate that is faster than the rate at which the kernel processes the packets.
Default setting: 300
4)/proc/sys/net/core/optmem_max
The file represents the size of the maximum buffer allowed for each socket.
Default setting: 10240
5)/proc/sys/net/core/rmem_default
The file specifies the default value, in bytes, to receive the socket buffer size.
Default setting: 110592
6)/proc/sys/net/core/rmem_max
The file specifies the maximum value, in bytes, of the receive socket buffer size.
Default setting: 131071
7)/proc/sys/net/core/wmem_default
The file specifies the default value (in bytes) for the send socket buffer size.
Default setting: 110592
8)/proc/sys/net/core/wmem_max
The file specifies the maximum size, in bytes, of the send socket buffer.
Default setting: 131071
9) to be continued ...
Six,/proc/sys/net/ipv4/optimization
1)/proc/sys/net/ipv4/ip_forward
The file indicates whether IP forwarding is turned on.
0, prohibit
1, forwarding
Default setting: 0
2)/proc/sys/net/ipv4/ip_default_ttl
This file represents the lifetime of a datagram (time to Live), which is the maximum number of routers to go through.
Default setting: 64
Increasing this value can degrade system performance.
3)/proc/sys/net/ipv4/ip_no_pmtu_disc
This file indicates that the path MTU detection function is turned off globally.
Default setting: 0
4)/PROC/SYS/NET/IPV4/ROUTE/MIN_PMTU
The file represents the size of the minimum path MTU.
Default setting: 552
5)/proc/sys/net/ipv4/route/mtu_expires
The file represents how long (in seconds) The PMTU information is cached.
Default setting: 600 (seconds)
6)/proc/sys/net/ipv4/route/min_adv_mss
The file represents the smallest MSS (Maximum Segment size), depending on the router MTU of the first hop.
Default setting: (bytes)
6.1 IP Fragmentation
1)/proc/sys/net/ipv4/ipfrag_low_thresh/proc/sys/net/ipv4/ipfrag_low_thresh
The two files represent the minimum and maximum memory allocations used to reorganize the IP segment, and once the maximum memory allocation value is reached, the other segments are discarded until the minimum memory allocation value is reached.
Default setting: 196608 (Ipfrag_low_thresh)
262144 (Ipfrag_high_thresh)
2)/proc/sys/net/ipv4/ipfrag_time
The file represents how many seconds an IP fragment is retained in memory.
Default setting: 30 (seconds)
6.2 INET Peer Storage
1)/proc/sys/net/ipv4/inet_peer_threshold
inet an appropriate value to the end of the memory, when exceeding the threshold entry will be discarded. This threshold also determines the survival
Time and the time interval at which the waste collection is passed. The more entries, the lower the survival period, and the shorter the GC interval.
Default setting: 65664
2)/proc/sys/net/ipv4/inet_peer_minttl
The minimum survival period for the entry. There must be enough fragmentation (fragment) survival time on the recombinant side. This minimum
The survival period must ensure that the buffer pool volume is less than inet_peer_threshold. The value is Jiffies
Unit measurements.
Default setting: 120
3)/proc/sys/net/ipv4/inet_peer_maxttl
Maximum lifetime of the entry. After this period arrives, if the buffer pool does not run out of pressure (for example: slow
The number of entries in the flush pool is very small), the unused entries will time out. The value is measured in jiffies.
Default setting: 600
4)/proc/sys/net/ipv4/inet_peer_gc_mintime
The shortest interval through which waste collection (GC) is passed. This interval affects the high pressure of memory in the buffer pool. This value
Measured in jiffies units.
Default setting: 10
2006-10-31 16:33 Qing Shiping
5)/proc/sys/net/ipv4/inet_peer_gc_maxtime
The maximum interval passed by the waste collection (GC), which affects the low pressure of memory in the buffer pool. This value
Measured in jiffies units.
Default setting: 120
6.3 TCP Variables
1)/proc/sys/net/ipv4/tcp_syn_retries
This file indicates the number of times that the native outbound TCP SYN Connection timed out retransmission should not be higher than 255, which is only for outgoing connections and is controlled by Tcp_retries1 for incoming connections.
Default setting: 5
2)/proc/sys/net/ipv4/tcp_keepalive_probes
The file represents the maximum number of TCP hold connection detections before a TCP connection is dropped. Keep the connection only in
The so_keepalive socket option is not sent until it is opened.
Default setting: 9 (Times)
3)/proc/sys/net/ipv4/tcp_keepalive_time
The file represents the number of seconds between the time the data is no longer being transmitted and the hold-to-connect signal is sent to the connection.
Default setting: 7200 (2 hours)
4)/PROC/SYS/NET/IPV4/TCP_KEEPALIVE_INTVL
This file represents the frequency at which TCP probes are sent, multiplied by tcp_keepalive_probes to indicate when there is no corresponding TCP connection.
Default setting: 75 (seconds)
5)/proc/sys/net/ipv4/tcp_retries1
The file represents the number of retransmissions that were made before the response to a TCP connection request was discarded.
Default setting: 3
6)/proc/sys/net/ipv4/tcp_retries2
This file indicates the number of retransmissions before a TCP packet has been established in the communication State.
Default setting: 15
7)/proc/sys/net/ipv4/tcp_orphan_retries
How many retries to make before the near-end drops the TCP connection. The default value is 7, which is equivalent to 50 seconds –
16 minutes, depending on RTO. If your system is a heavily loaded Web server, you may need to
To lower this value, this type of sockets can consume a lot of resources. Also reference
Tcp_max_orphans.
8)/proc/sys/net/ipv4/tcp_fin_timeout
For a socket connection that is disconnected at this end, TCP remains in the Fin-wait-2 state for the time. Each other May
Disconnects or does not end the connection or the unpredictable process dies. The default value is 60 seconds. Past in
The 2.2 version of the kernel is 180 seconds. You can set this value, but be aware that if your machine is negative
Load a heavy Web server, you may risk the memory being filled with a large number of invalid datagrams,
Fin-wait-2 sockets are less dangerous than fin-wait-1 because they eat up to 1.5K
Memory, but they exist for a longer period of time. In addition refer to Tcp_max_orphans.
Default setting: 60 (seconds)
9)/proc/sys/net/ipv4/tcp_max_tw_buckets
The maximum number of timewait sockets the system is processing at the same time. If this number is exceeded,
The time-wait socket is immediately removed and a warning message is displayed. The reason to set this limit, pure
In order to resist those simple DoS attacks, do not artificially reduce this limit, but if
Network conditions require more than the default value, you can increase it (and perhaps increase the memory).
Default setting: 180000
)/proc/sys/net/ipv4/tcp_tw_recyle
Turn on quick time-wait sockets recycling. Unless advised or requested by a technical expert, do not follow
Modify this value.
Default setting: 0
One)/proc/sys/net/ipv4/tcp_tw_reuse
The file indicates whether to allow the time-wait state of the socket to be re-applied for the new TCP connection.
Default setting: 0
/proc/sys/net/ipv4/tcp_max_orphans)
The maximum number of TCP sockets that the system can handle that is not part of any process. If it exceeds this amount, it
A connection that is not part of any process is immediately reset and a warning message is displayed. The reason to set this
To protect against simple DoS attacks, don't rely on this or artificially
Lower this limit.
Default setting: 8192
/proc/sys/net/ipv4/tcp_abort_on_overflow)
When the daemon is too busy to accept the new connection, the reset message is sent to the other party, and the default value is False.
This means that when the cause of the overflow is due to an accidental burst, then the connection will revert to the state. Only when you do
The message daemon really cannot complete the connection request until the option is turned on, which affects the customer's use.
Default setting: 0
/proc/sys/net/ipv4/tcp_syncookies)
The file indicates whether the TCP synchronization label (Syncookie) is turned on, and the kernel must have the Config_syn_cookies key open to compile. The Sync label (Syncookie) prevents a socket from overloading when there are too many attempts to connect.
Default setting: 0
/proc/sys/net/ipv4/tcp_stdurg)
Use the host Request interpretation feature in the TCP Urg pointer field. Most of the hosts are using the old
BSD explained, so if you open it on Linux, or it will cause you to not communicate properly with them.
Default setting: 0
/proc/sys/net/ipv4/tcp_max_syn_backlog)
For connection requests that still do not have a client acknowledgement, the maximum number that needs to be saved in the queue. For
Systems that exceed 128Mb of memory, the default value is 1024, or 128 less than 128Mb. If
The server is often overloaded and can try to increase this number. Warning! If you set this value to be greater than
1024, it is best to modify the include/net/tcp.h inside the tcp_synq_hsize to keep
tcp_synq_hsize*16 0) or bytes-bytes/2^ (-tcp_adv_win_scale) (e.g.
Tcp_adv_win_scale 128Mb 32768-610000) The system will ignore all sent to itself
Requests for ICMP echo requests or those broadcast addresses.
Default setting: 1024
/proc/sys/net/ipv4/tcp_window_scaling)
This file indicates whether the sliding window size of the TCP/IP session is set to variable. The value of the parameter is a Boolean value, 1 is variable, and 0 indicates immutable. TCP/IP typically uses a maximum of 65535 bytes of Windows, which may be too small for high-speed networks, which, if enabled, can increase the TCP/IP sliding window size by several orders of magnitude, increasing the ability to transmit data.
Default setting: 1
)/proc/sys/net/ipv4/tcp_sack
This file indicates whether a selective answer (selective acknowledgment) is enabled, which can improve performance by selectively answering packets received by the order (which allows the sender to send only the missing segment); (for WAN communication) This option should be enabled, However, this increases the CPU usage.
Default setting: 1
/proc/sys/net/ipv4/tcp_timestamps)
The file indicates whether to enable a more accurate method than a timeout (see RFC 1323) to enable calculation of RTT; This option should be enabled for better performance.
Default setting: 1
/proc/sys/net/ipv4/tcp_fack)
This file indicates whether to turn on fack congestion avoidance and fast retransmission functionality.
Default setting: 1
)/proc/sys/net/ipv4/tcp_dsack
This file indicates whether TCP is allowed to send "two identical" sack.
Default setting: 1
/PROC/SYS/NET/IPV4/TCP_ECN)
This file indicates whether the TCP direct congestion notification feature is turned on.
Default setting: 0
/proc/sys/net/ipv4/tcp_reordering)
The file represents the maximum number of reordered datagrams in the TCP stream.
Default setting: 3
)/proc/sys/net/ipv4/tcp_retrans_collapse
This file indicates whether the printer that has the bug is compatible with its bug.
Default setting: 1
/PROC/SYS/NET/IPV4/TCP_WMEM)
The file contains 3 integer values, respectively: Min,default,max
Min: Reserve the minimum amount of memory used to send buffers for the TCP socket. It can be used by each TCP socket.
Default: The amount of memory reserved for a TCP socket for sending buffers, which, by defaults, affects the value of default in Net.core.wmem used by other protocols, typically less than the default value in Net.core.wmem.
Max: reserves the maximum amount of memory used for sending buffers for TCP sockets. This value does not affect Net.core.wmem_max, and today the Select parameter So_sndbuf is not affected by this value. The default value is 128K.
Default setting: 4096 16384 131072
/PROC/SYS/NET/IPV4/TCP_RMEM)
The file contains 3 integer values, respectively: Min,default,max
Min: The amount of memory reserved for the TCP socket for receiving buffering, even if the TCP socket has at least so much memory to receive buffering in the event of a memory tension.
Default: The amount of memory reserved for the TCP socket for receiving buffering, which affects the value of default in the Net.core.wmem used by the other protocol. This value determines the TCP window size of 65535 in the case of default values for Tcp_adv_win_scale, Tcp_app_win, and Tcp_app_win.
Max: reserves the maximum amount of memory for the TCP socket to receive buffering. This value does not affect the value of Max in Net.core.wmem, and selecting the parameter so_sndbuf today is not affected by that value.
Default setting: 4096 87380 174760
/PROC/SYS/NET/IPV4/TCP_MEM)
The file contains 3 integer values, respectively: Low,pressure,high
Low: TCP does not consider freeing memory when TCP uses a number of memory pages that are below this value.
Pressure: When TCP uses more memory pages than this value, TCP attempts to stabilize its memory usage, enters pressure mode, and exits the pressure state when memory consumption falls below the low value.
High: Allows all TCP sockets the amount of pages used to queue buffered datagrams.
In general, these values are calculated based on the amount of system memory at system startup.
Default setting: 24576 32768 49152
/proc/sys/net/ipv4/tcp_app_win)
The file represents the number of reserved Max (Window/2^tcp_app_win, MSS) Windows due to application buffering. When 0 indicates that no buffering is required.
Default setting: 31
)/proc/sys/net/ipv4/tcp_adv_win_scale
The file represents the calculation buffer overhead bytes/2^tcp_adv_win_scale (if Tcp_adv_win_scale >; 0) or bytes-bytes/2^ (-tcp_adv_win_scale) (If tcp_adv_ Win_scale <= 0).
Default setting: 2
6.4 IP Variables
1)/proc/sys/net/ipv4/ip_local_port_range
The file represents the local port number that the TCP/UDP protocol opens.
Default setting: 1024 4999
Recommended settings: 32768 61000
2)/proc/sys/net/ipv4/ip_nonlocal_bind
The file indicates whether the process is allowed to state to a non-local address.
Default setting: 0
3)/proc/sys/net/ipv4/ip_dynaddr
This parameter is typically used in the case of a dial-up connection, which enables the system to immediately change the IP packet's source address to that IP address while interrupting the original TCP conversation and re-issuing a SYN request packet with the new address to start a new TCP conversation. When using IP spoofing, this parameter can immediately change the spoofed address to a new IP address. The file indicates whether dynamic addresses are allowed, if the value is not 0, and if the value is greater than 1, the kernel will record the dynamic address rewrite information via log.
Default setting: 0
4)/proc/sys/net/ipv4/icmp_echo_ignore_all/proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
This file indicates whether the kernel ignores all ICMP echo requests, or ignores broadcast and multicast requests.
0, responding to requests
1, ignore request
Default setting: 0
Recommended setting: 1
5)/proc/sys/net/ipv4/icmp_ratelimit
6)/proc/sys/net/ipv4/icmp_ratemask
7)/proc/sys/net/ipv4/icmp_ignore_bogus_error_reponses
Some routers violate the RFC1122 standard, which sends a forged response to the broadcast frame to answer. This violation of the line
It is usually logged in the system log as an alarm. If this option is set to true, the kernel does not
Record this warning message.
Default setting: 0
8)/proc/sys/net/ipv4/igmp_max_memberships
The file represents the maximum number of members in a multicast group.
Default setting: 20
6.5 Other Configuration
1)/proc/sys/net/ipv4/conf/*/accept_redirects
If there are two routers in the network segment where the host is located, you set one of them as the default gateway, but the gateway
When you receive your IP packet, you find that the IP packet must go through another router, and this router will give you
Sends a so-called "redirect" ICMP packet that tells the IP packet to be forwarded to another router. Parameter value is Boolean
Value, 1 for receiving such redirection ICMP information, 0 for ignoring. The Linux host that is acting as a router is missing
The save value is 0, and the default value is 1 on a typical Linux host. It is recommended that you change it to 0 to eliminate security risks.
2)/proc/sys/net/ipv4/*/accept_source_route
Whether to accept IP packets containing source routing information. The parameter value is a Boolean value, 1 is accepted, and 0 is not accepted. In
The default value is 1 on a Linux host that acts as a gateway, and the default value is 0 on a typical Linux host. From the security corner
It is recommended to turn this feature off.
3)/proc/sys/net/ipv4/*/secure_redirects
In fact, the so-called "security redirection" is to accept only "redirect" ICMP packets from the gateway. This parameter is
Used to set the "Security redirection" feature. The parameter value is a Boolean value, 1 means enabled, 0 is forbidden, and the default value
is enabled.
4)/proc/sys/net/ipv4/*/proxy_arp
Sets whether to relay ARP packets on the network. The parameter value is a Boolean value, 1 for trunk, 0 for ignore,
The default value is 0. This parameter is typically useful only for Linux hosts that act as routers.
Seven, performance optimization strategy
7.1 Basic Optimization
1) Turn off background daemon
When the system is installed, some daemon processes are started by default, and some processes are not required, so shutting down these processes can save a portion of the physical memory consumption. Log in to the system as root, run NTSYSV, and select the following process:
Iptables
Network
Syslog
Random
Apmd
xinetd
Vsftpd
Crond
Local
When you are finished modifying, restart the system.
Thus, the system will simply start the selected daemons.
2) Reduce the number of terminal connections
The system starts 6 terminals by default, and actually only needs to start 3, log in as root, run vi/etc/inittab, and modify it as follows:
# Run Gettys in standard runlevels
1:2345:respawn:/sbin/mingetty tty1
2:2345:respawn:/sbin/mingetty Tty2
3:2345:respawn:/sbin/mingetty Tty3
#4:2345:respawn:/sbin/mingetty Tty4
#5:2345:respawn:/sbin/mingetty tty5
#6:2345:respawn:/sbin/mingetty tty6
Comment out the 4, 5, and 6 terminals as described above.
3) to be continued ...
7.2 Network optimization
1) Optimizing the system socket buffer
net.core.rmem_max=16777216
net.core.wmem_max=16777216
2) Optimize TCP receive/send buffers
net.ipv4.tcp_rmem=4096 87380 16777216
net.ipv4.tcp_wmem=4096 65536 16777216
3) Optimize the network device receive queue
net.core.netdev_max_backlog=3000
4) Turn off routing-related features
Net.ipv4.conf.lo.accept_source_route=0
Net.ipv4.conf.all.accept_source_route=0
Net.ipv4.conf.eth0.accept_source_route=0
Net.ipv4.conf.default.accept_source_route=0
Net.ipv4.conf.lo.accept_redirects=0
Net.ipv4.conf.all.accept_redirects=0
Net.ipv4.conf.eth0.accept_redirects=0
Net.ipv4.conf.default.accept_redirects=0
Net.ipv4.conf.lo.secure_redirects=0
Net.ipv4.conf.all.secure_redirects=0
Net.ipv4.conf.eth0.secure_redirects=0
Net.ipv4.conf.default.secure_redirects=0
Net.ipv4.conf.lo.send_redirects=0
Net.ipv4.conf.all.send_redirects=0
Net.ipv4.conf.eth0.send_redirects=0
Net.ipv4.conf.default.send_redirects=0
5) Optimizing the TCP protocol stack
Open the TCP SYN cookie option to help protect the server from Syncflood attacks.
Net.ipv4.tcp_syncookies=1
Open the TIME-WAIT socket reuse feature, which is very effective for Web servers that have a large number of connections.
Net.ipv4.tcp_tw_recyle=1
Net.ipv4.tcp_tw_reuse=1
Reduces the time that is in the Fin-wait-2 connection state, allowing the system to handle more connections.
Net.ipv4.tcp_fin_timeout=30
Reduce the time of TCP keepalive connection detection, so that the system can handle more connections.
net.ipv4.tcp_keepalive_time=1800
Increase the TCP SYN queue length so that the system can handle more concurrent connections.
net.ipv4.tcp_max_syn_backlog=8192
(GO) Linux memory management--kernel Shmall and Shmmax parameters
