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<a class="post-title-link" href="/2019/06/10/linux软中断/" itemprop="url">linux软中断</a></h1>
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<p>中断是指操作系统响应硬件请求的一种机制，它会打断正常的进程正常的调度，然后调用内核中的中断处理程序来处理中断。 中断是一种异步的事件处理机制，可以提高系统的并发性。 由于会打断程序的执行，所以说中断处理程序就需要尽量的快。<br>中断处理程序在响应中断的时候，会临时停止别的中断。 比如说正在处理中断，由于处理的时间太长，别的中断经过几次重试后仍无法得到响应，就会丢失。 </p>
<p>怎么解决呢中断时间长和丢失的问题呢？</p>
<p>操作系统的中断将中断的处理分为上半部分和下半部分，分为硬中断和软中断。</p>
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<li>上半部分对应硬件中断，主要是快速响应中断</li>
<li>下半部分对应软中断，用来异步处理上半部分未完成的工作</li>
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<p>上半部分打断CPU当前正在执行的任务，然后立即执行中断程序。下半部分是以内核线程的方式执行，每个CPU都对应一个软中断的内核线程，命名为<code>ksoftirqd/CPU编号</code></p>
<p>比如 网卡接收到数据后，会通过硬中断的方式，通知内核有新数据到了。内核就调用中断处理程序处理他。<br>对于上半部分来讲，既然是快速处理，其实就是把网卡的数据读到内存中，然后更新一下硬件寄存器的状态，说数据已经准备好了。然后发一个软中断信号，下半部分的内核线程被中断信号唤醒，然后从内存中找到对应的数据，再按照协议栈，对数据逐层解析，再发给应用。</p>
<h3 id="如何查看中断"><a href="#如何查看中断" class="headerlink" title="如何查看中断"></a>如何查看中断</h3><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br></pre></td><td class="code"><pre><span class="line">cat /proc/softirqs</span><br><span class="line"> CPU0 CPU1 CPU2 CPU3</span><br><span class="line"> HI: 0 0 2 0</span><br><span class="line"> TIMER: 4148312434 13186832 2152909954 1619295093</span><br><span class="line"> NET_TX: 48 998 82 73</span><br><span class="line"> NET_RX: 679305939 2988243337 2907185894 1594980256</span><br><span class="line"> BLOCK: 0 0 0 0</span><br><span class="line">BLOCK_IOPOLL: 0 0 0 0</span><br><span class="line"> TASKLET: 4 327 19 3</span><br><span class="line"> SCHED: 2411399386 3393674518 2493384905 1990859404</span><br><span class="line"> HRTIMER: 0 0 0 0</span><br><span class="line"> RCU: 2964179126 2612143597 2807559860 2579168736</span><br><span class="line"> </span><br><span class="line">cat /proc/interrupts</span><br><span class="line"> CPU0 CPU1 CPU2 CPU3</span><br><span class="line"> 0: 66 0 0 0 IO-APIC-edge timer</span><br><span class="line"> 1: 10 0 0 0 IO-APIC-edge i8042</span><br><span class="line"> 4: 308 0 0 0 IO-APIC-edge serial</span><br><span class="line"> 6: 3 0 0 0 IO-APIC-edge floppy</span><br><span class="line"> 8: 0 0 0 0 IO-APIC-edge rtc0</span><br><span class="line"> 9: 0 0 0 0 IO-APIC-fasteoi acpi</span><br><span class="line"> 11: 0 0 0 0 IO-APIC-fasteoi uhci_hcd:usb1, virtio3</span><br><span class="line"> 12: 15 0 0 0 IO-APIC-edge i8042</span><br><span class="line"> 14: 0 0 0 0 IO-APIC-edge ata_piix</span><br><span class="line"> 15: 0 0 0 0 IO-APIC-edge ata_piix</span><br><span class="line"> 24: 0 0 0 0 PCI-MSI-edge virtio1-config</span><br><span class="line"> 25: 147682968 0 0 0 PCI-MSI-edge virtio1-req.0</span><br><span class="line"> 26: 0 0 0 0 PCI-MSI-edge virtio0-config</span><br><span class="line"> 27: 542900481 0 0 0 PCI-MSI-edge virtio0-input.0</span><br><span class="line"> 28: 14429 0 0 0 PCI-MSI-edge virtio0-output.0</span><br><span class="line"> 29: 1 629325029 0 0 PCI-MSI-edge virtio0-input.1</span><br><span class="line"> 30: 1 1503283 0 0 PCI-MSI-edge virtio0-output.1</span><br><span class="line"> 31: 1 0 2068524220 0 PCI-MSI-edge virtio0-input.2</span><br><span class="line"> 32: 1 0 345851 0 PCI-MSI-edge virtio0-output.2</span><br><span class="line"> 33: 1 0 0 1462076132 PCI-MSI-edge virtio0-input.3</span><br><span class="line"> 34: 1 0 0 26430 PCI-MSI-edge virtio0-output.3</span><br><span class="line"> 35: 0 0 0 0 PCI-MSI-edge virtio2-config</span><br><span class="line"> 36: 31425472 0 0 0 PCI-MSI-edge virtio2-req.0</span><br><span class="line">NMI: 0 0 0 0 Non-maskable interrupts</span><br><span class="line">LOC: 382083826 252345119 1860499022 948502231 Local timer interrupts</span><br><span class="line">SPU: 0 0 0 0 Spurious interrupts</span><br><span class="line">PMI: 0 0 0 0 Performance monitoring interrupts</span><br><span class="line">IWI: 317647455 304012392 287285894 266483309 IRQ work interrupts</span><br><span class="line">RTR: 0 0 0 0 APIC ICR read retries</span><br><span class="line">RES: 1381296847 379530962 1012267283 998082928 Rescheduling interrupts</span><br><span class="line">CAL: 3200050 53044096 49394276 47287849 Function call interrupts</span><br><span class="line">TLB: 36023588 39893743 36694448 36256223 TLB shootdowns</span><br><span class="line">TRM: 0 0 0 0 Thermal event interrupts</span><br><span class="line">THR: 0 0 0 0 Threshold APIC interrupts</span><br><span class="line">DFR: 0 0 0 0 Deferred Error APIC interrupts</span><br><span class="line">MCE: 0 0 0 0 Machine check exceptions</span><br><span class="line">MCP: 179217 179217 179217 179217 Machine check polls</span><br><span class="line">ERR: 0</span><br><span class="line">MIS: 0</span><br><span class="line">PIN: 0 0 0 0 Posted-interrupt notification event</span><br><span class="line">PIW: 0 0 0 0 Posted-interrupt wakeup event</span><br></pre></td></tr></table></figure>
<h3 id="软中断进程"><a href="#软中断进程" class="headerlink" title="软中断进程"></a>软中断进程</h3><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">ps aux | grep softirq</span><br><span class="line">root 3 0.0 0.0 0 0 ? S 2017 6:26 [ksoftirqd/0]</span><br><span class="line">root 13 0.0 0.0 0 0 ? S 2017 878:54 [ksoftirqd/1]</span><br><span class="line">root 18 0.0 0.0 0 0 ? S 2017 268:38 [ksoftirqd/2]</span><br><span class="line">root 23 0.0 0.0 0 0 ? S 2017 12:35 [ksoftirqd/3]</span><br></pre></td></tr></table></figure>
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<a class="post-title-link" href="/2019/06/06/linux性能优化实战-CPU/" itemprop="url">linux性能优化实战-CPU</a></h1>
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<h1 id="负载"><a href="#负载" class="headerlink" title="负载"></a>负载</h1><p>当我们发现系统很慢的时候，通过会查看系统的负载。 一般来讲会通过 top或这是 uptime命令</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"> top</span><br><span class="line">top - 17:15:48 up 622 days, 4:51, 9 users, load average: 5.01, 5.02, 5.05</span><br><span class="line">Tasks: 210 total, 1 running, 205 sleeping, 1 stopped, 3 zombie</span><br><span class="line"><span class="meta">%</span>Cpu(s): 0.3 us, 0.3 sy, 0.0 ni, 98.7 id, 0.8 wa, 0.0 hi, 0.0 si, 0.0 st</span><br><span class="line">KiB Mem : 8010528 total, 179432 free, 4879284 used, 2951812 buff/cache</span><br><span class="line">KiB Swap: 0 total, 0 free, 0 used. 2776264 avail Mem</span><br><span class="line"></span><br><span class="line"> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND</span><br><span class="line">22239 root 20 0 5652808 140536 4732 S 0.7 1.8 18:21.59 java</span><br><span class="line"> 6731 root 20 0 5657940 123540 3640 S 0.3 1.5 112:09.73 java</span><br><span class="line">10219 redis 20 0 474672 336468 384 S 0.3 4.2 315:43.34 redis-server</span><br><span class="line">10274 root 20 0 571320 15488 2484 S 0.3 0.2 14:07.64 YDService</span><br><span class="line">24606 root 20 0 0 0 0 S 0.3 0.0 0:00.54 kworker/0:0</span><br><span class="line"></span><br><span class="line">uptime</span><br><span class="line"> 17:16:22 up 622 days, 4:51, 9 users, load average: 5.05, 5.04, 5.05</span><br></pre></td></tr></table></figure>
<p>上边的load average: 5.05, 5.04, 5.05 就是系统的平均负载了。 分别代表过去1分钟，5分钟，15分钟的平均负载。 这给我们提供了分析系统负载趋势的数据源。<br>可以观察 过去15分钟内的负载的变化</p>
<p>那什么是平均负载呢？<br><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">man uptime</span><br><span class="line">System load averages is the average number of processes that are either in a runnable or uninterruptable state. A process in a runnable state is either using the CPU or waiting to use the CPU. </span><br><span class="line">A process in uninterruptable state is waiting for some I/O access, eg waiting for disk. The averages are taken over the three time intervals. Load averages are not normalized for the number of CPUs in a system, so a load average of 1 means a single CPU system is loaded all the time while on a 4 CPU system it means it was idle 75% of the time.</span><br></pre></td></tr></table></figure></p>
<p>平均负载就是单位时间里，进程状态为runnable(状态为R Running or Runnable)或者是uninterruptable(状态为D Disk sleep)的进程数。<br>不可中断是操作系统对于硬件的一种保护措施，是内核态执行的。</p>
<p>如果你有4个CPU，如果负载是4 那就说明CPU全部被占满了，资源得到了最大的利用。</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">查看cpu数</span><br><span class="line">grep 'model name' /proc/cpuinfo | wc -l</span><br><span class="line">2</span><br></pre></td></tr></table></figure>
<blockquote>
<p>当平均负载在70%CPU数量的时候比较合适</p>
</blockquote>
<p>负载高不代表CPU的使用率高。</p>
<ul>
<li>CPU密集型的程序，负载应该和CPU数一致</li>
<li>IO密集型的进程，IO负载会高，CPU使用率不一定会高</li>
<li>大量等待CPU调度的进程也会造成load变高，CPU也会随之升高</li>
</ul>
<p>apt install systat</p>
<p>常用的一些命令包括 top, mpstat, pidstat, uptime</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">mpstat -P ALL 1 -u</span><br><span class="line">Linux 3.10.0-514.26.2.el7.x86_64 (tx-relay1.common.bj.tx.lan) 2019年06月06日 _x86_64_ (4 CPU)</span><br><span class="line"></span><br><span class="line">18时08分38秒 CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle</span><br><span class="line">18时08分39秒 all 42.86 0.00 21.94 0.26 0.00 0.26 0.00 0.00 0.00 34.69</span><br><span class="line">18时08分39秒 0 38.14 0.00 21.65 0.00 0.00 0.00 0.00 0.00 0.00 40.21</span><br><span class="line">18时08分39秒 1 37.37 0.00 21.21 0.00 0.00 1.01 0.00 0.00 0.00 40.40</span><br><span class="line">18时08分39秒 2 47.96 0.00 20.41 0.00 0.00 0.00 0.00 0.00 0.00 31.63</span><br><span class="line">18时08分39秒 3 47.47 0.00 24.24 2.02 0.00 0.00 0.00 0.00 0.00 26.26</span><br><span class="line"></span><br><span class="line">pidstat -u -p 25397</span><br><span class="line">Linux 3.10.0-514.26.2.el7.x86_64 (tx-relay1.common.bj.tx.lan) 2019年06月06日 _x86_64_ (4 CPU)</span><br><span class="line"></span><br><span class="line">18时14分24秒 UID PID %usr %system %guest %CPU CPU Command</span><br><span class="line">18时14分24秒 1038 25397 0.00 0.00 0.00 0.00 2 python</span><br></pre></td></tr></table></figure>
<h1 id="CPU上下文切换"><a href="#CPU上下文切换" class="headerlink" title="CPU上下文切换"></a>CPU上下文切换</h1><h1 id="短时进程"><a href="#短时进程" class="headerlink" title="短时进程"></a>短时进程</h1><h1 id="大量不可中断进程"><a href="#大量不可中断进程" class="headerlink" title="大量不可中断进程"></a>大量不可中断进程</h1><h1 id="大量僵尸进程"><a href="#大量僵尸进程" class="headerlink" title="大量僵尸进程"></a>大量僵尸进程</h1><h1 id="linux软中断"><a href="#linux软中断" class="headerlink" title="linux软中断"></a>linux软中断</h1><p>中断是指操作系统响应硬件请求的一种机制，它会打断正常的进程正常的调度，然后调用内核中的中断处理程序来处理中断。 中断是一种异步的事件处理机制，可以提高系统的并发性</p>
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<a class="post-title-link" href="/2019/06/06/SRE-方法论/" itemprop="url">SRE-方法论</a></h1>
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<p>SRE是指Site Reliability Engineer (网站可靠性工程师)。他是软件工程师和系统管理员的结合，一个SRE工程师基本上需要掌握很多知识：算法，数据结构，编程能力，网络编程，分布式系统，可扩展架构，故障排除。</p>
<p>SRE成员的特点：</p>
<ul>
<li>对重复性、手工性的操作有天然的排斥感</li>
<li>有足够的技术能力快速开发软件以代替手工操作</li>
</ul>
<p>SRE通过设计、构建自动化的工具来取代人工操作。 通过操作代码来管理机器，而不是人直接去管理机器。</p>
<h1 id="确保长期关注研发工作"><a href="#确保长期关注研发工作" class="headerlink" title="确保长期关注研发工作"></a>确保长期关注研发工作</h1><p>限制运维工作在50%以内。 以保证大部分时间都在研发工作上.<br>how？</p>
<ol>
<li>处理问题一天不要超过2个紧急事件。运维人员需要跟进每一个问题，把问题的原委搞清楚才能得到成长和改进。</li>
<li>尽量将问题转给研发团队。</li>
<li>轮班on-call，把时间分配开</li>
<li>少做手动操作，把手动操作自动化以节省时间</li>
</ol>
<h1 id="在保证服务SLO的前提下最大化迭代速度。"><a href="#在保证服务SLO的前提下最大化迭代速度。" class="headerlink" title="在保证服务SLO的前提下最大化迭代速度。"></a>在保证服务SLO的前提下最大化迭代速度。</h1><p>最主要的矛盾是迭代创新的速度与产品稳定程度之间的矛盾。<br>在SRE模型中，我们正面对这些矛盾，使用的工具是<code>错误预算</code>。</p>
<p>首先，任何产品都不可能保证100%的可靠信，所以我们需要根据实际情况，设置一个我们可以实现并且用户可以接受的可靠性的指标。<br>比如我们的用户的可以接受的可靠性是99%，那错误预算就是1%，我们可以使用错误预算最大化的保证新功能的上线速度，用于做一些创新和正常的业务需求.</p>
<p>可靠性的目标可以考虑以下几个方面:</p>
<ul>
<li>服务的可靠性达到多少用户才会满意呢？</li>
<li>用户是否有其他的替代方案</li>
<li>是否会影响用户的使用模式</li>
</ul>
<h1 id="监控系统"><a href="#监控系统" class="headerlink" title="监控系统"></a>监控系统</h1><p>监控系统可以衡量一个系统的可用性和质量的重要手段。 简单来说就是收集各层的性能或者是业务指标，然后加以聚合和汇总，呈现出动态的视图。可以针对这些指标设置阈值和规则，进行各种各样的报警。 如Email、短信等。<br>但是这样的报警策略并不是很有效的需要人去处理，人需要阅读错误信息，再去排查问题，这本身就是错误的。理想状态下，监控系统应该能自己分析报警信息，然后自动决策， 或者是给出合理的建议，让人去选择。</p>
<h1 id="应急事件处理"><a href="#应急事件处理" class="headerlink" title="应急事件处理"></a>应急事件处理</h1><p>MTTF(平均失败时间)和MTTR(平均恢复时间)，是评价一个团队将系统恢复到正常的最有效的指标。<br>出现故障后，如果能通过自动故障处理的程序把系统恢复那再好不过了。不过有好些情况还是需要人工干预的。 通过事先预案并且将最佳方法记录在”运维手册“中，这样可以有效的降低MTTR.<br>学过武功秘籍的人去解决问题，自然会快一些和高效一些. 而且随着时间的推移，运维手册会不断的完善。也方便对新人做培训</p>
<h1 id="变更管理"><a href="#变更管理" class="headerlink" title="变更管理"></a>变更管理</h1><p>经验来讲，70%的生产事故来源于变更。变更管理的最佳事件使用自动化来完成以下项目：</p>
<ul>
<li>渐进式发布机制。 - 减少受影响面积</li>
<li>迅速而准确的检测到问题的发生。 - 减少故障时间</li>
<li>出现问题时可以自动的快速回滚。 - 减少故障时间</li>
</ul>
<h1 id="需求预测和容量规划"><a href="#需求预测和容量规划" class="headerlink" title="需求预测和容量规划"></a>需求预测和容量规划</h1><p>保障业务有足够的容量和冗余度来服务预测中的外来的需求。</p>
<p>容量规划必须有几个必要的步骤:</p>
<ul>
<li>必须有一个准确的自然增长需求预测模型，需求预测的时间应该超过资源获取的时间。</li>
<li>规划中必须有准确的非自然增长的需求来源的统计</li>
<li>必须有周期性压力测试，以便准确地将系统原始资源信息与业务容量对应起来。</li>
</ul>
<h1 id="资源部署"><a href="#资源部署" class="headerlink" title="资源部署"></a>资源部署</h1><p>SRE要负责资源的部署。 添加新的资源可以是机器、或者是集群，当然添加过后还需要改动对应的配置，如负载均衡等等，这些都会对整体的稳定性有些影响，不过这个k8s下目前还是比较简单的。 </p>
<h1 id="效率与性能"><a href="#效率与性能" class="headerlink" title="效率与性能"></a>效率与性能</h1><p>一个是高效的利用资源的，提升利用率。这样可以更加节省成本。SRE需要提高资源的利用率。 一个业务总资源使用情况由以下几个因素：</p>
<ul>
<li>用户流量 </li>
<li>可用容量 </li>
<li>资源利用率</li>
</ul>
<p>SRE可以通过需求模型的预测和监控数据来优化资源的使用率。</p>
<p>延迟在负载高的情况下会上升，当负载到达临界值的时候，系统会逐渐变慢，甚至全部停止。SRE可以通过设置预期的延迟目标和维护足够的容量解决这个问题。</p>
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