【hotplug】热拔插模式:
→和ondemand模式差不多,当有高需求时直接跳到最高频率,当需求见效时逐级降低频率,
但关屏时就单核低频运行,省电。
【ondemand】按需模式:
→按需调节cpu频率,不操作手机的时候控制在最低频率,滑屏或进入应用后会迅速提升至最
高频率,当空闲时迅速降低频率,性能较稳定,但因频率变化幅度过大,省电方面只有一般的水
平。是一种在电池和性能之间趋向平衡的默认模式,但是对于智能手机来说,ondemand在性
能表现方面略有欠缺。
【userspace】用户模式:
→任何情况下都会控制CPU运行在配置的频率范围内,配置中的用户自己添加的省电设置。
在此情景模式下,降低CPU最大运行频率可以延长电池待机时间,但同时也会降低机器的唤
醒速度,建议最好不使用该选项。
【interactive】交互模式:
→和ondemand相似,规则是“快升慢降”,注重响应速度、性能,当有高需求时迅速跳到高频率,
当低需求时逐渐降低频率,相比ondemand费电
【performance】高性能模式:
→高性能模式,按你设定范围的最高频率运行,即使系统负载非常低cpu的频率也为最高。性能
很好,因为CPU本身不需要资源去调整频率,但是电量消耗较快,温度也高一些。
本文已收录于以下专栏：
相关文章推荐
设备节点的创建，是通过sysfs接口分析dev文档取得设备节点号，这个很显而易见。那么udevd是通过什么机制来得知内核里模块的变化情况，如何得知设备的插入移除情况呢？当然是通过hotplug机制了，...
CPU hotplug Support
in Linux(tm) Kernel                  &#...
网络绝对是任何系统的核心，对于容器而言也是如此。Docker 作为目前最火的轻量级容器技术，有很多令人称道的功能，如 Docker 的镜像管理。然而，Docker的网络一直以来都比较薄弱，所以我们有必要深入了解Docker的网络知识，以满足更高的网络需求。
CPU 热插拔, 或者是 online/offline, 是 linux 支持的一个功能.
要使用这个拱
PCIE的hotplug操作讨论
hotplug的概念
hotplug--热插拔即“带电插拔”，指可以在电脑系统运作时插上或拔除硬件设备。配合适当的软件，便可以在不用关闭电源的情况下插入或拔除支持...
这篇文章，讲述了“阿里云服务器申请的步骤”，希望能够帮助到您！
String 和StringBuffer的区别：
JAVA平台提供了两个类：String和StringBuffer，它们可以储存和操作字符串，即包含多个字符的字符数据。这个String类提供了数值不...
本系列将对比新浪云、百度云、腾讯云、阿里云、微软云、青云
获取ES某个索引下的数据总量
引包import net.sf.json.JSONO
import mons.logging.L
他的最新文章
讲师：王渊命
讲师：蔡栋
您举报文章：
举报原因：
原文地址：
原因补充：
(最多只允许输入30个字)cpu热插拔什么意思
输入手机号码，报价结果将发送到您手机
装修顾问-馨馨
4年行业经验，24h可咨询
10秒闪电通过好友
报价短信已发送到您的手机
因材料品牌及工程量不同，具体报价以量房实测为准
稍候装修管家将回电您，免费提供装修咨询服务
您的装修预算约
*装修管家将回电您，免费提供装修咨询服务
*装修管家将回电您，免费提供装修咨询服务
*因材料品牌及工程量不同，具体报价以量房实测为准
装修顾问 -馨馨
（四年装修行业经验）
微信扫一扫
3.&您家小区名称 :&&
请选择您家的装修时间
cpu热插拔什么意思
我来帮他解答
还可以输入1500字
已有3条回答
回答数：2157
被采纳数：16
热插拔即“带电插拔”，指可以在电脑运作时插上或拔除硬件。配合适当的软件，便可以在不用关闭电源的情况下插入或拔除支持热插拔的周边设备，不会导致主机或周边设备烧毁并且能够实时侦测及使用新的设备。相比随插即用，热插拔对软硬件的要求还包含了电源、信号与接地线的接触顺序。
回答数：20536
被采纳数：132
热插拔是说在电源流通的情况下拔掉除usb之外的数据插头，在热插拔的情况下很容易烧点cpu或是其他重要硬盘。
回答数：29109
被采纳数：46
就是通电的情况下拔，肯定不支持啦，CPU不是插拔的，是安装的，CPU上面还要装风扇散热呢。通电的情况下主板是不能随便拔插
位业主已在问吧找到答案
北欧简约、复古美式、大气欧式、清新地中海风，总有一款适合你！Linux CPU Hotplug CPU热插拔 - 海王 - 博客园
随笔 - 548
http://blog.chinaunix.net/uid--id-106930.html
CPU hotplug Support in Linux(tm) Kernel
Linux支持CPU的热插拔功能
&&&&&&&&&&&&&&&&&& Maintainers:
&&&&&&&&&&&&&&&&&& CPU Hotplug Core:&&&&&&&&&&&&&&&&&&&&&&&&&&&& Rusty Russell&&.au&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Srivatsa Vaddagiri&&vatsa@&&&&&&&&&&&&&&&&&&& i386:&&&&&&&&&&&&&&&&&&&&&&&&&&&& Zwane Mwaikambo&&zwane@arm.linux.org.uk&&&&&&&&&&&&&&&&&&& ppc64:&&&&&&&&&&&&&&&&&&&&&&&&&&&& Nathan Lynch&&nathanl@&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Joel Schopp&&jschopp@&&&&&&&&&&&&&&&&&&& ia64/x86_64:&&&&&&&&&&&&&&&&&&&&&&&&&&&& Ashok Raj&&ashok.&&&&&&&&&&&&&&&&&&& s390:&&&&&&&&&&&&&&&&&&&&&&&&&&&& Heiko Carstens&&heiko.carstens@&Authors: Ashok Raj&&ashok.&Lots of feedback: Nathan Lynch&&nathanl@&,&&&&&&&&&&&&&& Joel Schopp&&jschopp@&IntroductionModern advances in system architectures have introduced advanced errorreporting and correction capabilities in processors. CPU architectures permitpartitioning support, where compute resources of a single CPU could be madeavailable to virtual machine environments. There are couple OEMS thatsupport NUMA hardware which are hot pluggable as well, where physicalnode insertion and removal require support for CPU hotplug.Such advances require CPUs available to a kernel to be removed either forprovisioning reasons, or for RAS purposes to keep an offending CPU offsystem execution path. Hence the need for CPU hotplug support in theLinux kernel.A more novel use of CPU-hotplug support is its use today in suspendresume support for SMP. Dual-core and HT support makes evena laptop run SMP kernels which didn't support these methods. SMP supportfor suspend/resume is a work in progress.现 在，在一些先进的体系结构中处理器引进了一些先进的错误报告和错误修正能力。CPU体系结构上允许CPU分割，把分割的一部分CPU作为一个可用的虚拟机 器环境。有很多NUAM结构的硬件设备支持设备热插拔功能，比如说NUMA结构的计算机一个物理节点的插入和移出需要CPU热插拔功能的支持。如此先进的功能需要操作系统能够提供必要条件满足CPU的热插拔功能的实现。或者因为远程访问服务器有意去使某个CPU不在系统的执行路径上（即这个CPU不能再次被使用）。这些都要求Linux操作系统支持CPU的热插拔功能。现在很多对称多处理器的机器（SMP）使用CPU热插拔功能。双核和高可用技术使得便携式电脑都能使用SMP内核的操作系统，但是不能实现CPU热插拔功能。SMP支持CPU暂停或恢复当作一个任务在系统运行过程中。General Stuff about CPU Hotplug（关于CPU热插拔常常碰到的一些技术与问题）--------------------------------Command Line Switches（命令行开关，就是通过命令行的执行，对一些数据项和操作的开\关设置）---------------------maxcpus=n&&&& Restrict boot time cpus to n. Say if you have 4 cpus, using&&&&&&&&&&&& maxcpus=2 will only boot 2. You can choose to bring the&&&&&&&&&&&& other cpus later online, read FAQ's for more info.&&&&&&&&&&&&&&&&&&&&&&&&&&&&这个数据项用来限制机器启动时启动CPU的数目。如果你的机器有4个CPU，你将maxcpus设置为2，那么在机器启动时只能启动2个CPU。你可以在机器完全启动后，可以将剩下的CPU热添加进系统。additional_cpus=n (*)&&&&&& Use this to limit hotpluggable cpus. This option sets&&&&&&&&&&&&&&&&&&&&&&&&&& cpu_possible_map = cpu_present_map + additional_cpus&&&&&&&&&&&&&&&&&&&&&&&&&&&使用这个命令行可以限制可以热添加的CPU数目。下面等式表示系统中几个描述CPU位图之间的关系。&&&&&&&&&&&& 系统中可以允许最大数目CPU=系统中目前现有的CPU数目+添加进去的CPU数目(*) Option valid only for following architectures- x86_64, ia64（只针对X86_64和ia64体系结构的CPU）ia64 and x86_64 use the number of disabled local apics in ACPI tables MADTto determine the number of potentially hot-pluggable cpus. The implementationshould only rely on this to count the # of cpus, but *MUST* not rely on theapicid values in those tables for disabled apics. In the event BIOS doesn'tmark such hot-pluggable cpus as disabled entries, one could use thisparameter "additional_cpus=x" to represent those cpus in the cpu_possible_map.ia64和x86_64芯片使用ACPI的MADT表中大量的被禁用的局部APICs（Advanced Programmable Interrupt Controllers，高级可编程中断控制器）决定这些CPU作为潜在的热插拔CPU。possible_cpus=n&&&&&&&&&&&&&&&& [s390 only] use this to set hotpluggable cpus.&&&&&&&&&&&&&&&&&&&&&&&&&&&& This option sets possible_cpus bits in&&&&&&&&&&&&&&&&&&&&&&&&&&&& cpu_possible_map. Thus keeping the numbers of bits set&&&&&&&&&&&&&&&&&&&&&&&&&&&& constant even if the machine gets rebooted.CPU maps and such-----------------[More on cpumaps and primitive to manipulate, please checkcpu_possible_map: Bitmap of possible CPUs that can ever be available in thesystem. This is used to allocate some boot time memory for per_cpu variablesthat aren't designed to grow/shrink as CPUs are made available or removed.Once set during boot time discovery phase, the map is static, i.e no bitsare added or removed anytime.&& Trimming it accurately for your system needsupfront can save some boot time memory. See below for how we use heuristicsin x86_64 case to keep this under check.cpu_possible_map： 系统中可能所有可用的CPU的位图结构变量。一般在系统引导启动的时候为每个可能存在的CPU分配内存给per_cpu变量。这些不是用来描述CPU的热 添加或热移出操作。这个位图是个静态变量，在系统引导启动时候生成后，就不能修改了。cpu_online_map: Bitmap of all CPUs currently online. Its set in __cpu_up()after a cpu is available for kernel scheduling and ready to receiveinterrupts from devices. Its cleared when a cpu is brought down using__cpu_disable(), before which all OS services including interrupts aremigrated to another target CPU.cpu_online_map： 系统当前online的CPU。这个位图在函数__cpu_up()中被设置，这个位图描述了系统有哪些CPU可以用来调度执行任务和可以接受设备中断。 当执行函数__cpu_disable()时，清除指定CPU在位图cpu_online_map对应的位，这就意味着指定的CPU不可用了，不过这个函 数执行之前，要将指定CPU上所有的服务和中断迁移到其他CPU上执行。cpu_present_map: Bitmap of CPUs currently present in the system. Not allof them may be online. When physical hotplug is processed by the relevantsubsystem (e.g ACPI) can change and new bit either be added or removedfrom the map depending on the event is hot-add/hot-remove. There are currentlyno locking rules as of now. Typical usage is to init topology during boot,at which time hotplug is disabled.cpu_present_map： 当前系统存在的CPU。但是，并不是所有存在的CPU都处于online。在物理上的CPU热插拔依据相关的子系统处理，会改变位图 cpu_present_map相应位的值。该位图经典地用于在系统启动时描述系统CPU拓扑结构，并且那时候CPU的hotplug功能被禁用了。You really dont need to manipulate any of the system cpu maps. They shouldbe read-only for most use. When setting up per-cpu resources almost always usecpu_possible_map/for_each_possible_cpu() to iterate.你并不需要熟练使用系统地CPU这些位图。因为他们通常只读。通过cpu_possible_map/for_each_possible_cpu()反复使用为每个CPU建立必需资源。Never use anything other than cpumask_t to represent bitmap of CPUs.在系统中所有的CPU位图都是cpumask_t类型的数据结构。&&&&&&&& #include&&&&&&&&& for_each_possible_cpu&&&& - Iterate over cpu_possible_map&&&&&&&& for_each_online_cpu&&&&&& - Iterate over cpu_online_map&&&&&&&& for_each_present_cpu&&&&&& - Iterate over cpu_present_map&&&&&&&& for_each_cpu_mask(x,mask) - Iterate over some random collection of cpu mask.&&&&&&&& #include&&&&&&&&& get_online_cpus() and put_online_cpus():The above calls are used to inhibit cpu hotplug operations. While thecpu_hotplug.refcount is non zero, the cpu_online_map will not change.If you merely need to avoid cpus going away, you could also usepreempt_disable() and preempt_enable() for those sections.Just remember the critical section cannot call anyfunction that can sleep or schedule this process away. The preempt_disable()will work as long as stop_machine_run() is used to take a cpu down.上 面提到的所有函数（例程）用于阻止CPU的热插拔操作。当cpu_hotplug的引用计数不为0时，位图cpu_online_map不会发生改变。如 果你仅仅只是需要避免CPU的消失，你同样可以调用preempt_disable()和preempt_enable()。记住在临界区不能调用任何函 数因为那样可能会被睡眠或者中断。当执行stop_machine_run()函数使一个CPU不可用时，一定会调用执行 preempt_disable()。CPU Hotplug - Frequently Asked Questions.（CPU热插拔常见问题）Q: How to enable my kernel to support CPU hotplug?该怎样激活我的操作系统内核才能支持CPU热插拔？A: When doing make defconfig, Enable CPU hotplug support&& "Processor type and Features" -& Support for Hotpluggable CPUsMake sure that you have CONFIG_HOTPLUG, and CONFIG_SMP turned on as well.You would need to enable CONFIG_HOTPLUG_CPU for SMP suspend/resume supportas well.在你配置内核选项时，即在终端输入&make menuconfig&，将会出现一个蓝色界面，将需要的选项打开即可。
Q: What architectures support CPU hotplug?
&A: As of 2.6.14, the following architectures support CPU hotplug.&i386 (Intel), ppc, ppc64, parisc, s390, ia64 and x86_64&Q: How to test if hotplug is supported on the newly built kernel?怎么测试最新编译的内核是否支持CPU热插拔操作。&A: You should now notice an entry in sysfs.&Now you should see entries for all present cpu, the following is an example&in a 8-way system.&&&&&&&&&&#pwd&&&&&&&&& #/sys/devices/system/cpu&&&&&&&&& #ls -l&&&&&&&&& total 0&&&&&&&&& drwxr-xr-x&& 10 root root 0 Sep 19 07:44 .&&&&&&&&& drwxr-xr-x&& 13 root root 0 Sep 19 07:45 ..&&&&&&&&& drwxr-xr-x&& 3 root root 0 Sep 19 07:44 cpu0&&&&&&&&& drwxr-xr-x&& 3 root root 0 Sep 19 07:44 cpu1&&&&&&&&& drwxr-xr-x&& 3 root root 0 Sep 19 07:44 cpu2&&&&&&&&&&drwxr-xr-x&& 3 root root 0 Sep 19 07:44 cpu3&&&&&&&&& drwxr-xr-x&& 3 root root 0 Sep 19 07:44 cpu4&&&&&&&&& drwxr-xr-x&& 3 root root 0 Sep 19 07:44 cpu5&&&&&&&&& drwxr-xr-x&& 3 root root 0 Sep 19 07:44 cpu6&&&&&&&&& drwxr-xr-x&& 3 root root 0 Sep 19 07:48 cpu7&Under each directory you would find an "online" file which is the control&file to logically online/offline a processor.&在每个目录下可以看见一个&online&文件，该文件描述的所属CPU是否online&Q: Does hot-add/hot-remove refer to physical add/remove of cpus?是否CPU热插拔支持物理CPU添加和移出？&A: The usage of hot-add/remove may not be very consistently used in the code.&CONFIG_HOTPLUG_CPU enables logical online/offline capability in the kernel.&To support physical addition/removal, one would need some BIOS hooks and&the platform should have something like an attention button in PCI hotplug.&CONFIG_ACPI_HOTPLUG_CPU enables ACPI support for physical add/remove of CPUs.&CPU逻辑上的热插拔处理是在linux内核的代码完成。支持物理上CPU热插拔，需要BIOS支持以及硬件平台的支持比如像PCI设备热插拔以类似的硬件支持&Q: How do i logically offline a CPU?我该怎么将一个CPU逻辑上热移出。&A: Do the following.&&&&&&&&&#echo 0 & /sys/devices/system/cpu/cpuX/online（在终端里，输本行命令即可）&Once the logical offline is successful, check（检查是否成功将CPU热移出）&&&&&&&&& #cat /proc/interrupts（在终端里，输本行命令即可）&You should now not see the CPU that you removed. Also online file will report&the state as 0 when a cpu if offline and 1 when its online.&在&online&文件里描述CPU的状态，0代表已经移出，1代表已经添加成功&&&&&&&&& #To display the current cpu state.&&&&&&&&#cat /sys/devices/system/cpu/cpuX/online&Q: Why cant i remove CPU0 on some systems?&A: Some architectures may have some special dependency on a certain CPU.&For e.g in IA64 platforms we have ability to sent platform interrupts to the&OS. a.k.a Corrected Platform Error Interrupts (CPEI). In current ACPI&specifications, we didn't have a way to change the target CPU. Hence if the&current ACPI version doesn't support such re-direction, we disable that CPU&by making it not-removable.&In such cases you will also notice that the online file is missing under cpu0.&Q: How do i find out if a particular CPU is not removable?&A: Depending on the implementation, some architectures may show this by the&absence of the "online" file. This is done if it can be determined ahead of&time that this CPU cannot be removed.&In some situations, this can be a run time check, i.e if you try to remove the&last CPU, this will not be permitted. You can find such failures by&investigating the return value of the "echo" command.&Q: What happens when a CPU is being logically offlined?当一个CPU逻辑热移出时，内核放生了什么？&A: The following happen, listed in no particular order :-)&- A notification is sent to in-kernel registered modules by sending an event&&& CPU_DOWN_PREPARE or CPU_DOWN_PREPARE_FROZEN, depending on whether or not the&&& CPU is being offlined while tasks are frozen due to a suspend operation in&&& progress&将事件CPU_DOWN_PREPARE 或者 CPU_DOWN_PREPARE_FROZEN发送到内核中&- All processes are migrated away from this outgoing CPU to new CPUs.&&& The new CPU is chosen from each process' current cpuset, which may be&&& a subset of all online CPUs.&将所有进程从目标CPU迁移到系统其他CPU上运行。&- All interrupts targeted to this CPU is migrated to a new CPU&将所有中断从目标CPU迁移到其他CPU&- timers/bottom half/task lets are also migrated to a new CPU&计时器和下半部迁移到其他CPU&- Once all services are migrated, kernel calls an arch specific routine&&& __cpu_disable() to perform arch specific cleanup.&当所有服务迁移后，内核调用例程__cpu_disable()执行体系结构特定的清除操作&- Once this is successful, an event for successful cleanup is sent by an event&&& CPU_DEAD (or CPU_DEAD_FROZEN if tasks are frozen due to a suspend while the&&& CPU is being offlined).&一旦成功地将CPU热移出，就会发送CPU_DEAD。&&& "It is expected that each service cleans up when the CPU_DOWN_PREPARE&&& notifier is called, when CPU_DEAD is called its expected there is nothing&&& running on behalf of this CPU that was offlined"&希望在执行通知链上CPU_DOWN_PREPARE操作时完成所有服务的清除操作。当执行通知链上CPU_DEAD的操作时，希望没有任何服务在CPU上执行，因为CPU已经成功地被移出。&Q: If i have some kernel code that needs to be aware of CPU arrival and&&& departure, how to i arrange for proper notification?&A: This is what you would need in your kernel code to receive notifications.&&&&&&&&& #include&&&&&&&&& static int __cpuinit foobar_cpu_callback(struct notifier_block *nfb,&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& unsigned long action, void *hcpu)&&&&&&&&& {&&&&&&&&&&&&&&&&&&& unsigned int cpu = (unsigned long)&&&&&&&&&&&&&&&&&&& switch (action) {&&&&&&&&&&&&&&&&&&& case CPU_ONLINE:&&&&&&&&&&&&&&&&&&& case CPU_ONLINE_FROZEN:&&&&&&&&&&&&&&&&&&&&&&&&&&&&& foobar_online_action(cpu);&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& case CPU_DEAD:&&&&&&&&&&&&&&&&&&& case CPU_DEAD_FROZEN:&&&&&&&&&&&&&&&&&&&&&&&&&&&&& foobar_dead_action(cpu);&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& }&&&&&&&&&&&&&&&&&&& return NOTIFY_OK;&&&&&&&&& }&&&&&&&&& static struct notifier_block __cpuinitdata foobar_cpu_notifer =&&&&&&&&& {&&&&&&&&&&&&& .notifier_call = foobar_cpu_callback,&&&&&&&&& };&You need to call register_cpu_notifier() from your init function.&Init functions could be of two types:&1. early init (init function called when only the boot processor is online).&2. late init (init function called _after_ all the CPUs are online).&For the first case, you should add the following to your init function&&&&&&&&& register_cpu_notifier(&foobar_cpu_notifier);&For the second case, you should add the following to your init function&&&&&&&&& register_hotcpu_notifier(&foobar_cpu_notifier);&You can fail PREPARE notifiers if something doesn't work to prepare resources.&This will stop the activity and send a following CANCELED event back.&CPU_DEAD should not be failed, its just a goodness indication, but bad&things will happen if a notifier in path sent a BAD notify code.&Q: I don't see my action being called for all CPUs already up and running?&A: Yes, CPU notifiers are called only when new CPUs are on-lined or offlined.&&& If you need to perform some action for each cpu already in the system, then&&&&&&&&& for_each_online_cpu(i) {&&&&&&&&&&&&&&&&&&& foobar_cpu_callback(&foobar_cpu_notifier, CPU_UP_PREPARE, i);&&&&&&&&&&&&&&&&&&& foobar_cpu_callback(&foobar_cpu_notifier, CPU_ONLINE, i);&&&&&&&&& }&Q: If i would like to develop cpu hotplug support for a new architecture,&&& what do i need at a minimum?&A: The following are what is required for CPU hotplug infrastructure to work&&& correctly.&&&&& - Make sure you have an entry in Kconfig to enable CONFIG_HOTPLUG_CPU&&&&& - __cpu_up()&&&&&&&& - Arch interface to bring up a CPU&&&&& - __cpu_disable()&& - Arch interface to shutdown a CPU, no more interrupts&&&&&&&&&&&&&&&&&&&&&&&&&&& can be handled by the kernel after the routine&&&&&&&&&&&&&&&&&&&&&&&&&&& returns. Including local APIC timers etc are&&&&&&&&&&&&&&&&&&&&&&&&&&& shutdown.&&&&& - __cpu_die()&&&&&& - This actually supposed to ensure death of the CPU.&&&&&&&&&&&&&&&&&&&&&&&&&&& Actually look at some example code in other arch&&&&&&&&&&&&&&&&&&&&&&&&&&& that implement CPU hotplug. The processor is taken&&&&&&&&&&&&&&&&&&&&&&&&&&& down from the idle() loop for that specific&&&&&&&&&&&&&&&&&&&&&&&&&&& architecture. __cpu_die() typically waits for some&&&&&&&&&&&&&&&&&&&&&&&&&&& per_cpu state to be set, to ensure the processor&&&&&&&&&&&&&&&&&&&&&&&&&&& dead routine is called to be sure positively.&Q: I need to ensure that a particular cpu is not removed when there is some&&& work specific to this cpu is in progress.&A: First switch the current thread context to preferred cpu&&&&&&&&& int my_func_on_cpu(int cpu)&&&&&&&&& {&&&&&&&&&&&&&&&&&&& cpumask_t saved_mask, new_mask = CPU_MASK_NONE;&&&&&&&&&&&&&&&&&&& int curr_cpu, err = 0;&&&&&&&&&&&&&&&&&&& saved_mask = current-&cpus_&&&&&&&&&&&&&&&&&&& cpu_set(cpu, new_mask);&&&&&&&&&&&&&&&&&&& err = set_cpus_allowed(current, new_mask);&&&&&&&&&&&&&&&&&&& if (err)&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& /*&&&&&&&&&&&&&&&&&&&&& * If we got scheduled out just after the return from&&&&&&&&&&&&&&&&&&&&& * set_cpus_allowed() before running the work, this ensures&&&&&&&&&&&&&&&&&&&&& * we stay locked.&&&&&&&&&&&&&&&&&&&&& */&&&&&&&&&&&&&&&&&&& curr_cpu = get_cpu();&&&&&&&&&&&&&&&&&&& if (curr_cpu != cpu) {&&&&&&&&&&&&&&&&&&&&&&&&&&&&& err = -EAGAIN;&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& } else {&&&&&&&&&&&&&&&&&&&&&&&&&&&&& /*&&&&&&&&&&&&&&&&&&&&&&&&&&&&& * Do work : But cant sleep, since get_cpu() disables preempt&&&&&&&&&&&&&&&&&&&&&&&&&&&&& */&&&&&&&&&&&&&&&&&&& }&&&&&&&&&&&&&&&&&&& ret:&&&&&&&&&&&&&&&&&&&&&&&&&&&&& put_cpu();&&&&&&&&&&&&&&&&&&&&&&&&&&&&& set_cpus_allowed(current, saved_mask);&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& }&Q: How do we determine how many CPUs are available for hotplug.&A: There is no clear spec defined way from ACPI that can give us that&&& information today. Based on some input from Natalie of Unisys,&&& that the ACPI MADT (Multiple APIC Description Tables) marks those possible&&& CPUs in a system with disabled status.&&& Andi implemented some simple heuristics that count the number of disabled&&& CPUs in MADT as hotpluggable CPUS.&& In the case there are no disabled CPUS&&& we assume 1/2 the number of CPUs currently present can be hotplugged.&&& Caveat: Today's ACPI MADT can only provide 256 entries since the apicid field&&& in MADT is only 8 bits.&User Space Notification&Hotplug support for devices is common in Linux today. Its being used today to&support automatic configuration of network, usb and pci devices. A hotplug&event can be used to invoke an agent script to perform the configuration task.&You can add /etc/hotplug/cpu.agent to handle hotplug notification user space&scripts.&&&&&&&&& #!/bin/bash&&&&&&&&& # $Id: cpu.agent&&&&&&&&& # Kernel hotplug params include:&&&&&&&&& #ACTION=%s [online or offline]&&&&&&&&& #DEVPATH=%s&&&&&&&&& #&&&&&&&&& cd /etc/hotplug&&&&&&&&& . ./hotplug.functions&&&&&&&&& case $ACTION in&&&&&&&&&&&&&&&&&&& online)&&&&&&&&&&&&&&&&&&&&&&&&&&&&& echo `date` ":cpu.agent" add cpu && /tmp/hotplug.txt&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ;;&&&&&&&&&&&&&&&&&&& offline)&&&&&&&&&&&&&&&&&&&&&&&&&&&&& echo `date` ":cpu.agent" remove cpu &&/tmp/hotplug.txt&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ;;&&&&&&&&&&&&&&&&&&& *)&&&&&&&&&&&&&&&&&&&&&&&&&&&&& debug_mesg CPU $ACTION event not supported&&&&&&&&& exit 1&&&&&&&&& ;;&&&&&&&&& esac
阅读(...) 评论()
Copyright & 海王
Powered by:
模板提供：}