sysctl | 易学教程

Why no error when setting socket send/receive buffer size higher than sysctl max?

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问题 Why no error when setting socket send/receive buffer size higher than sysctl max (as I have demonstrated below)? is no error the "expected behavior"? My sysctl values for socket rmem_max and wmem_max are both set to 212992: net.core.rmem_default = 212992 net.core.rmem_max = 212992 net.core.wmem_default = 212992 net.core.wmem_max = 212992 net.ipv4.tcp_rmem = 4096 87380 6291456 net.ipv4.tcp_wmem = 4096 16384 4194304 net.ipv4.udp_rmem_min = 4096 net.ipv4.udp_wmem_min = 4096 vm.lowmem_reserve

Invalid argument“ setting key ”net.core.somaxconn"

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问题 I tried setting Linux kernel. After editing /etc/sysctl.conf and executing the sysctl -p it shows error Invalid argument" setting key "net.core.somaxconn" Linux distribution: Ubuntu 12.04.4 LTS, x86_64, 3.2.0-60-generic $ cat /etc/sysctl.conf net.ipv4.conf.eth0.arp_notify = 1 vm.swappiness = 0 net.ipv4.tcp_rmem = 4096 87380 4194304 net.ipv4.tcp_wmem = 4096 16384 4194304 net.core.wmem_default = 8388608 net.core.rmem_default = 8388608 net.core.rmem_max = 16777216 net.core.wmem_max = 16777216

Invalid argument“ setting key ”net.core.somaxconn"

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Why is sysctl producing E_INVAL on Mac OS X?

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问题 Below is a pared-down (error/null checks omitted) snippet of C/Obj-C code that uses sysctl to get the argv of a particular process with PID 50. ... int getProcessArgs[3] = { CTL_KERN, KERN_PROCARGS, 50 }; sysctl(getProcessArgs, 3, NULL, &length, NULL, 0); char* processArgs = malloc(length * sizeof(char)); sysctl(getProcessArgs, 3, processArgs, &length, NULL, 0); ... The first call to sysctl (to determine the size of the argv string array) succeeds. The returned length is ~1600, larger than I

Android Edit Sysctl Settings

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问题 In my app i need to edit sysctl settings in Android. I've seen few apps that can do this, for example but i have no idea how do they do this programmatically, any ideas how to do this? 回答1: I think i found the answer: sysctl.conf is located in the /system/etc folder. Ask for the root and edit it like any other text file. Ask for the root - How can I get root permissions through the Android SDK? Edit text file - http://www.java-samples.com/showtutorial.php?tutorialid=1523 来源： https:/

Dynamically adding entries to sysctl

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问题 Consider this code: int procmon_state = 0; static struct ctl_table_header *procmon_table_header; static ctl_table state_table[] = { { .procname = "state", .mode = 0666, .proc_handler = &proc_dointvec_minmax, .data = &procmon_state, .maxlen = sizeof(int), .extra1 = "\x00\x00\x00\x00" /*0*/, .extra2 = "\x01\x00\x00\x00" /*1*/ }, { 0 } }; static ctl_table procmon_table[] = { { .procname = "procmon", .mode = 0555, .child = state_table }, { 0 } }; procmon_table_header = register_sysctl_table

Calling “sysctlbyname(…)” with “hw.machine” flag in iOS9

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问题 Following WWDC 2015 session "703 Privacy and Your App", there is changes using sysctl . And now there we will no longer be able to call kern.proc , kern.procargs , kern.procargs2 and see data from any other processes then one's self. It's a quite legit privacy hardening by Apple. Can anyone confirm that calling sysctlbyname(...) with hw.machine to fetch exact device name is allowed in iOS9 and not affected by restriction mentioned above? 回答1: Yes ,I have tested it Using Xcode7 beta5 in

iOS cpu usage for each process using sysctl()?

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问题 Is there a way to get cpu usage for each process using sysctl() ? I'm trying to find a way to detect the launch of a specific application. It seems there's no way to get foreground running app information. So I guess if I can monitor cpu usage for that specific app I can monitor the cpu usage changes and roughly assume when the app launches. Is this possible at all? I'm not planning to publish this app to apple appstore. This is only a research. So if there is ANY way to do this I'm glad to

浅谈linux性能调优之十五:常见网络参数整理

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 1.tcp连接保持管理： net.ipv4.tcp_keepalive_time = 7200 如果在该参数指定时间内某条连接处于空闲状态，则内核向远程主机发起探测 net.ipv4.tcp_keepalive_intvl = 75 内核向远程主机发送的保活探测的时间间隔 net.ipv4.tcp_keepalive_probes = 9 内核发送保活探测的最大次数，如果探测次数大于这个数，则断定远程主机不可达，则关闭该连接并释放本地资源一个连接7200s空闲后，内核会每隔75秒去重试，若连续9次则放弃。这样就导致一个连接经过2h11min的时间才能被丢弃，降低该值能够尽量减小失效连接所占用的资源，而被新的连接所使用。 2.tcp连接管理： net.core.netdev_max_backlog=3000 该文件表示在每个网络接口接收数据包的速率比内核处理这些包的速率快时，允许送到队列的数据包的最大数目。 net.ipv4.tcp_max_syn_backlog = 1024 控制每个端口的tcp syn的队列长度，来自客户端的连接请求需要排队，直至服务器接受，如果连接请求数大于该值，则连接请求会被丢弃，客户端无法连接服务器，一般服务器要提高此值 net.ipv4.tcp_synack_retries =

Solving Redis warnings on overcommit_memory and Transparent Huge Pages for Ubuntu 16.04 on EC2

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问题 On a fresh Ubuntu 16.04 EC2 instance the warnings appear like so: WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect. WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo