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第7章CPU调度【精选-PPT】
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第7章CPU调度【精选-PPT】
关注微信公众号> 告别四大误区 谈缓存对CPU的性能影响
告别四大误区 谈缓存对CPU的性能影响CNET中国·ZOL
缓存及工作原理介绍：
　　要想发挥出优异的性能，除了与核心架构有关之外，缓存的作用也是功不可没。那什么是的缓存呢？其实很好解释，缓存（Cache Memoney）就是位于CPU与之间的临时存储器，它的容量比内存小但数据交换速率却快很多。
【图】处理器缓存工作原理
　　缓存的工作原理是当CPU要读取一个数据时，首先从缓存中查找，如果找到就立即读取并送给CPU处理；如果没有找到，就用相对慢的速度从内存中读取并送给CPU处理，同时把这个数据所在的数据块调入缓存中，可以使得以后对整块数据的读取都从缓存中进行，不必再调用内存。
【图】处理器缓存构造
　　正是这样的读取机制使CPU读取缓存的命中率非常高（大多数CPU可达90%左右），也就是说CPU下一次要读取的数据90%都在缓存中，只有大约10%需要从内存读取。这大大节省了CPU直接读取内存的时间，也使CPU读取数据时基本无需等待。总的来说，CPU读取数据的顺序是先缓存后内存。
【图】L2级缓存
　　在高速运转的处理器缓存世界中，事实上还有很多不为大众所了解的“内幕”，今天笔者将围绕很多玩家还存在的四种认识误区展开，感兴趣的玩家一定不要错过哦。 缓存认识上的一些误区
　　错误观点一：缓存可以用来取代
【图】拥有的 65nm四核心Kentsfield处理器
　　处理器缓存的传输速率确实很高，然而还不足以取代内存的地位，这主要是由于缓存只是内存中少部分数据的复制品，所以到缓存中寻找数据时，也会出现找不到的情况（因为这些数据没有从内存复制到缓存中去），这时还是会到内存中去找数据。与此同时系统的速度就慢了下来，不过CPU会把这些数据复制到缓存中去，以便下一次不用再到内存中去取。就目前缓存容量、成本以及功耗表现来看，还远远无法与内存抗衡，另外从某种意义上来说，内存也是处理器缓存的一种表现形式，只不过在速率上慢很多，然而却在容量、功耗以及成本方面拥有巨大优势。如果内存在将来可以做到足够强的话，反而很有取代处理器缓存的可能。
　　错误观点二：处理器缓存是一个整体
【图】生产技术对缓存容量大小的影响
【图】PCB上带缓存的PentiumIII处理器
　　事实上最早先的CPU缓存确实是个整体，而且容量也很低。英特尔公司从Pentium时代开始后就把缓存进行了分类，当时集成在CPU内核中的缓存已不足以满足CPU的需求，而制造工艺上的限制又不能大幅度提高缓存的容量。因此出现了集成在与CPU同一块电路板上或上的缓存，此时就把CPU内核集成的缓存称为一级缓存，而外部的称为二级缓存；后来随着生产技术的不断提高，最终二级缓存也被挪进了处理器当中。通常一级缓存中还分数据缓存（Data Cache，D-Cache）和指令缓存（Instruction Cache，I-Cache）。二者分别用来存放数据和执行这些数据的指令，而且两者可以同时被CPU访问，减少了争用Cache所造成的冲突，提高了处理器效能。英特尔公司在推出Pentium 4处理器时，还新增了一种一级追踪缓存，容量为12KB。
　　错误观点三：L1级缓存和L2级缓存只有容量上的差别
　　用于存储数据的缓存部分通常被称为RAM，掉电以后其中的信息就会消失。RAM又分两种，其中一种是静态RAM（SRAM）；另外一种是动态RAM（DRAM）。前者的存储速度要比后者快得多，我们现在使用的内存一般都是动态RAM。处理器的L1级缓存通常都是静态RAM，速度非常的快，但是静态RAM集成度低（存储相同的数据，静态RAM的体积是动态RAM的6倍），而且也相对较为昂贵（同容量的静态RAM是动态RAM的四倍）。扩大静态RAM作为缓存是一个不太合算的做法，但是为了提高系统的性能和速度又必须要扩大缓存，这就有了一个折中的方法：在不扩大原来的静态RAM缓存容量的情况下，仅仅增加一些高速动态RAM做为L2级缓存。高速动态RAM速度要比常规动态RAM快，但比原来的静态RAM缓存慢，而且成本也较为适中。一级缓存和二级缓存中的内容都是内存中访问频率高的数据的复制品（映射），它们的存在都是为了减少高速CPU对慢速内存的访问。 缓存认识上的一些误区
　　二级缓存是性能表现的关键之一，在核心不变化的情况下，增加二级缓存容量能使性能大幅度提高。而同一核心的CPU高低端之分往往也是在二级缓存上存在差异，由此可见二级缓存对CPU的重要性。CPU在缓存中找到有用的数据被称为命中，当缓存中没有CPU所需的数据时（这时称为未命中），CPU才访问。从理论上讲，在一颗拥有二级缓存的CPU中，读取一级缓存的命中率为80%。也就是说CPU一级缓存中找到的有用数据占数据总量的80%，剩下的20%从二级缓存中读取。由于不能准确预测将要执行的数据，读取二级缓存的命中率也在80%左右（从二级缓存读到有用的数据占总数据的16%）。那么还有的数据就不得不从内存调用，但这已经是一个相当小的比例了。目前的较高端CPU中，还会带有三级缓存，它是为读取二级缓存后未命中的数据设计的—种缓存，在拥有三级缓存的CPU中，只有约5%的数据需要从内存中调用，这进一步提高了CPU的效率，从某种意义上说，预取效率的提高，大大降低了生产成本却提供了非常接近理想状态的性能。除非某天生产技术变得非常强，否则内存仍会存在，缓存的性能递增特性也仍会保留。
　　错误观点四：缓存只是随意调取数据并无选择
　　即便内部集成的缓存数据交换能力非常强，也仍需要对调取数据做一定的筛选。这是因为随着时间的变化，被访问得最频繁的数据不是一成不变的，也就是说，刚才还不频繁的数据，此时已经需要被频繁的访问，刚才还是最频繁的数据，现在又不频繁了，所以说缓存中的数据要经常按照一定的算法来更换，这样才能保证缓存中的数据经常是被访问最频繁的。命中率算法中较常用的“最近最少使用算法”（LRU算法），它是将最近一段时间内最少被访问过的行淘汰出局。因此需要为每行设置一个计数器，LRU算法是把命中行的计数器清零，其他各行计数器加1。当需要替换时淘汰行计数器计数值最大的数据行出局。这是一种高效、科学的算法，其计数器清零过程可以把一些频繁调用后再不需要的数据淘汰出缓存，提高缓存的利用率。
【图】拥有144MB缓存的八路IBM POWER5处理器
　　总结：
　　高速缓存做为处理器不可分割的一部分，已经融入到性能提升的考虑因素当中，伴随生产技术的进一步发展，缓存的级数还将增加，容量也会进一步提高。作为处理器性能助推器的高速缓存，仍会在成本和功耗控制方面发挥巨大的优势，而性能方面也会取得长足的发展。可以毫不夸张的说：缓存技术带领处理器走进了一个多姿多彩的全新世界。
&相关阅读：
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1、进BIOS由默认值改为优化设置值，将开机启动顺序设硬盘为第一启动。
2、禁用闲置的IDE通道
右键点击“我的电脑－属性”--“硬件”--“设备管理器”，在其中展开“IDE ATA/PATA控制器”然后分别右击“主要”和“次要”IDE通道--“高级设置”--将“设备类型”设置为“无”，将“传送模式”设为“DMA（若可用”。
3、优化视觉效果
右键单击“我的电脑”--“属性”—“高级”，在“性能”栏中，点击“设置”--“视觉效果”，调整为最佳性能，或去掉一些不需要的功能。
4、优化性能
右键单击“我的电脑”--“属性”—“高级”，在“性能”栏中，点击“设置”—“高级”—将“处理器计划”、“内存使用”，均选“程序”。
接着单击“虚拟内存”区“更改”--在驱动器列表中选中系统盘符--自定义大小--在“初始大小”和“最大值”中设定数值，然后单击“设置”按钮，最后点击“确定”按钮退出。虚拟内存最小值物理内存1.5—2倍，最大值为物理内存的2—3倍。
5、启动和故障恢复
"我的电脑"--"属性"--"高级"--"启动和故障修复"--“设置”，在“系统失败区中，去掉"将事件写入系统日志"，"发送管理警报"，"自动重新启动"前边的勾;将"写入调试信息"设置为"无"；点击"编辑"，在弹出记事本文件中:[Operating Systems] timeout=30 把 30 秒改为 0 秒。
【有网友说】
台式机默认状态下，CPU已经是最大的效能了，大多都以最高的频率运行，部分主板会根据不同的情况自动调节。使用cpufreq-bench评估cpufreq策略对系统性能的影响 - CSDN博客
使用cpufreq-bench评估cpufreq策略对系统性能的影响
Linux 3.1已经将cpupower-utils中放入内核的tools目录，见：
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.a=f=tools/h=f6a98ba1f53bb8cb67f59112adf346;hb=c3b92cbb53d57d5cc96
在其中有一个工具叫cpufreq-bench，可以用于测试ondemand等cpufreq策略的使用对系统性能的影响，譬如：
# /usr/sbin/cpufreq-bench -l 50000 -s 100000 -x 50000 -y 100000 -g ondemand -r 5 -n 5 -v
loading defaults
parsing: sleep -& 50000
parsing: load -& 50000
parsing: cpu -& 0
parsing: priority -& LOW
parsing: output -& /var/log/cpufreq-bench
logilename: /var/log/cpufreq-bench/benchmark_localhost_2.6.38.8-xxx_1686167.log
Logfile: /var/log/cpufreq-bench/benchmark_localhost_2.6.38.8-xxx_1686167.log
parsing: sleep_step -& 50000
parsing: load_step -& 50000
parsing: cycles -& 20
parsing: rounds -& 40
parsing: verbose -& 0
parsing: governor -& ondemand
user load time -& 50000
user sleep time -& 100000
user load_step -& 50000
user sleep_step -& 100000
user governor -& ondemand
user rounds -& 5
user cycles -& 5
verbose output enabled
starting benchmark with parameters:
&&&&&&& sleep=100000
&&&&&&& load=50000
&&&&&&& sleep_step=100000
&&&&&&& load_step=50000
&&&&&&& cpu=0
&&&&&&& cycles=5
&&&&&&& rounds=5
&&&&&&& governor=ondemand
approx. test duration: 0m
set cpu affinity to cpu #0
set affinity to cpu #0
low priority condition requested
set scheduler priority to 0
set performance as cpufreq governor
calibrating load of 50000us, please wait...
calibrating with 6 rounds
calibrating with 6 rounds
calibrating with 6 rounds
calibrating with 6 rounds
calibration done
_round 1: doing 5 cycles with 6 calculations for 50000us
avarage: 8333us, rps:120
performance cycle took 147613us, sleep: 100000us, load: 50000us, rounds: 6
performance cycle took 211700us, sleep: 100000us, load: 50000us, rounds: 6
performance cycle took 147747us, sleep: 100000us, load: 50000us, rounds: 6
performance cycle took 147537us, sleep: 100000us, load: 50000us, rounds: 6
performance cycle took 147482us, sleep: 100000us, load: 50000us, rounds: 6
set ondemand as cpufreq governor
powersave cycle took 149627us, sleep: 100000us, load: 50000us, rounds: 6
powersave cycle took 243281us, sleep: 100000us, load: 50000us, rounds: 6
powersave cycle took 288620us, sleep: 100000us, load: 50000us, rounds: 6
powersave cycle took 288554us, sleep: 100000us, load: 50000us, rounds: 6
powersave cycle took 290043us, sleep: 100000us, load: 50000us, rounds: 6
performance is at 39.74%
set performance as cpufreq governor
calibrating load of 100000us, please wait...
calibrating with 12 rounds
calibrating with 12 rounds
calibrating with 12 rounds
calibrating with 12 rounds
calibration done
_round 2: doing 5 cycles with 12 calculations for 100000us
avarage: 8333us, rps:120
performance cycle took 296126us, sleep: 200000us, load: 100000us, rounds: 12
performance cycle took 296454us, sleep: 200000us, load: 100000us, rounds: 12
performance cycle took 296068us, sleep: 200000us, load: 100000us, rounds: 12
performance cycle took 296026us, sleep: 200000us, load: 100000us, rounds: 12
performance cycle took 295887us, sleep: 200000us, load: 100000us, rounds: 12
set ondemand as cpufreq governor
powersave cycle took 479989us, sleep: 200000us, load: 100000us, rounds: 12
powersave cycle took 464829us, sleep: 200000us, load: 100000us, rounds: 12
powersave cycle took 389619us, sleep: 200000us, load: 100000us, rounds: 12
powersave cycle took 514207us, sleep: 200000us, load: 100000us, rounds: 12
powersave cycle took 473326us, sleep: 200000us, load: 100000us, rounds: 12
performance is at 36.35%
set performance as cpufreq governor
calibrating load of 150000us, please wait...
calibrating with 18 rounds
calibrating with 18 rounds
calibrating with 18 rounds
calibrating with 18 rounds
calibration done
_round 3: doing 5 cycles with 18 calculations for 150000us
avarage: 8333us, rps:120
performance cycle took 445176us, sleep: 300000us, load: 150000us, rounds: 18
performance cycle took 445219us, sleep: 300000us, load: 150000us, rounds: 18
performance cycle took 444955us, sleep: 300000us, load: 150000us, rounds: 18
performance cycle took 445073us, sleep: 300000us, load: 150000us, rounds: 18
performance cycle took 445084us, sleep: 300000us, load: 150000us, rounds: 18
set ondemand as cpufreq governor
powersave cycle took 563155us, sleep: 300000us, load: 150000us, rounds: 18
powersave cycle took 598616us, sleep: 300000us, load: 150000us, rounds: 18
powersave cycle took 614820us, sleep: 300000us, load: 150000us, rounds: 18
powersave cycle took 618511us, sleep: 300000us, load: 150000us, rounds: 18
powersave cycle took 619225us, sleep: 300000us, load: 150000us, rounds: 18
performance is at 47.91%
set performance as cpufreq governor
calibrating load of 200000us, please wait...
calibrating with 24 rounds
calibrating with 25 rounds
calibrating with 25 rounds
calibrating with 25 rounds
calibration done
_round 4: doing 5 cycles with 25 calculations for 200000us
avarage: 8000us, rps:125
performance cycle took 602496us, sleep: 400000us, load: 200000us, rounds: 25
performance cycle took 602759us, sleep: 400000us, load: 200000us, rounds: 25
performance cycle took 602782us, sleep: 400000us, load: 200000us, rounds: 25
performance cycle took 602688us, sleep: 400000us, load: 200000us, rounds: 25
performance cycle took 602433us, sleep: 400000us, load: 200000us, rounds: 25
set ondemand as cpufreq governor
powersave cycle took 756766us, sleep: 400000us, load: 200000us, rounds: 25
powersave cycle took 774079us, sleep: 400000us, load: 200000us, rounds: 25
powersave cycle took 778619us, sleep: 400000us, load: 200000us, rounds: 25
powersave cycle took 779616us, sleep: 400000us, load: 200000us, rounds: 25
powersave cycle took 779655us, sleep: 400000us, load: 200000us, rounds: 25
performance is at 54.22%
set performance as cpufreq governor
calibrating load of 250000us, please wait...
calibrating with 30 rounds
calibrating with 31 rounds
calibrating with 31 rounds
calibrating with 31 rounds
calibration done
_round 5: doing 5 cycles with 31 calculations for 250000us
avarage: 8064us, rps:124
performance cycle took 752761us, sleep: 500000us, load: 250000us, rounds: 31
performance cycle took 751929us, sleep: 500000us, load: 250000us, rounds: 31
performance cycle took 752054us, sleep: 500000us, load: 250000us, rounds: 31
performance cycle took 751597us, sleep: 500000us, load: 250000us, rounds: 31
performance cycle took 751791us, sleep: 500000us, load: 250000us, rounds: 31
set ondemand as cpufreq governor
powersave cycle took 958276us, sleep: 500000us, load: 250000us, rounds: 31
powersave cycle took 928743us, sleep: 500000us, load: 250000us, rounds: 31
powersave cycle took 921301us, sleep: 500000us, load: 250000us, rounds: 31
powersave cycle took 920670us, sleep: 500000us, load: 250000us, rounds: 31
powersave cycle took 920122us, sleep: 500000us, load: 250000us, rounds: 31
performance is at 58.64%
上述测试结果可以看出，被测试平台ondemand采用后，性能下降很大：
Round 1 - 39.74%
Round 2 - 36.35%
Round 3 - 47.91%
Round 4 - 54.22%
Round 5 - 58.64%
比较理想的结果是，ondemand采用后性能维持在performance策略的90％左右：
cpufreq-bench results with optimization on OMAP:
Round 1 - 90.24%
Round 2 - 94.48%
Round 3 - 96.06%
Round 4 - 96.6%
Round 5 - 86.89%
cpufreq-bench results on X86 platform:
Round 1 - 88.67%
Round 2 - 94.71%
Round 3 - 95.53%
Round 4 - 96.34%
Round 5 - 98.03%
由此可见，被测平台的cpufreq驱动相关参数还需要深度调整。
我们在同样的平台上测试Android添加的interactive这个cpufreq策略的性能：
#/usr/sbin/cpufreq-bench -l 50000 -s 100000 -x 50000 -y 100000 -g interactive -
r 5 -n 5 -v
loading defaults
parsing: sleep -&50000
parsing: load -&50000
parsing: cpu -& 0
parsing: priority-& LOW
parsing: output -&/var/log/cpufreq-bench
logilename:/var/log/cpufreq-bench/benchmark_localhost_2.6.38.8-xxx_6470.log
Logfile:/var/log/cpufreq-bench/benchmark_localhost_2.6.38.8-xxx_6470.log
parsing: sleep_step-& 50000
parsing: load_step-& 50000
parsing: cycles -&20
parsing: rounds -&40
parsing: verbose-& 0
parsing: governor-& ondemand
user load time -&50000
user sleep time -&100000
user load_step -&50000
user sleep_step -&100000
user governor -&interactive
user rounds -& 5
user cycles -& 5
verbose outputenabled
starting benchmarkwith parameters:
&&&&&&& sleep=100000
&&&&&&& load=50000
&&&&&&& sleep_step=100000
&&&&&&& load_step=50000
&&&&&&& cpu=0
&&&&&&& cycles=5
&&&& &&&rounds=5
&&&&&&& governor=interactive
approx. testduration: 0m
set cpu affinity tocpu #0
set affinity to cpu#0
low prioritycondition requested
set schedulerpriority to 0
set performance ascpufreq governor
calibrating load of50000us, please wait...
calibrating with 6rounds
calibrating with 6rounds
calibrating with 6rounds
calibrating with 6rounds
calibration done
_round 1: doing 5cycles with 6 calculations for 50000us
avarage: 8333us,rps:120
performance cycletook 147635us, sleep: 100000us, load: 50000us, rounds: 6
performance cycletook 147506us, sleep: 100000us, load: 50000us, rounds: 6
performance cycletook 147590us, sleep: 100000us, load: 50000us, rounds: 6
performance cycletook 147755us, sleep: 100000us, load: 50000us, rounds: 6
performance cycletook 147563us, sleep: 100000us, load: 50000us, rounds: 6
set interactive ascpufreq governor
powersave cycle took166866us, sleep: 100000us, load: 50000us, rounds: 6
powersave cycle took164004us, sleep: 100000us, load: 50000us, rounds: 6
powersave cycle took165926us, sleep: 100000us, load: 50000us, rounds: 6
powersave cycle took163750us, sleep: 100000us, load: 50000us, rounds: 6
powersave cycle took165789us, sleep: 100000us, load: 50000us, rounds: 6
performance is at 72.95%
set performance ascpufreq governor
calibrating load of100000us, please wait...
calibrating with 12rounds
calibrating with 12rounds
calibrating with 12rounds
calibrating with 12rounds
calibration done
_round 2: doing 5cycles with 12 calculations for 100000us
avarage: 8333us,rps:120
performance cycletook 296382us, sleep: 200000us, load: 100000us, rounds: 12
performance cycletook 296349us, sleep: 200000us, load: 100000us, rounds: 12
performance cycletook 296266us, sleep: 200000us, load: 100000us, rounds: 12
performance cycletook 296152us, sleep: 200000us, load: 100000us, rounds: 12
performance cycletook 295848us, sleep: 200000us, load: 100000us, rounds: 12
set interactive ascpufreq governor
powersave cycle took314330us, sleep: 200000us, load: 100000us, rounds: 12
powersave cycle took308119us, sleep: 200000us, load: 100000us, rounds: 12
powersave cycle took309546us, sleep: 200000us, load: 100000us, rounds: 12
powersave cycle took309942us, sleep: 200000us, load: 100000us, rounds: 12
powersave cycle took309673us, sleep: 200000us, load: 100000us, rounds: 12
performance is at 87.20%
set performance ascpufreq governor
calibrating load of150000us, please wait...
calibrating with 18rounds
calibrating with 18rounds
calibrating with 18rounds
calibrating with 18rounds
calibration done
_round 3: doing 5cycles with 18 calculations for 150000us
avarage: 8333us,rps:120
performance cycletook 445460us, sleep: 300000us, load: 150000us, rounds: 18
performance cycletook 445368us, sleep: 300000us, load: 150000us, rounds: 18
performance cycletook 445724us, sleep: 300000us, load: 150000us, rounds: 18
performance cycletook 445194us, sleep: 300000us, load: 150000us, rounds: 18
performance cycletook 445266us, sleep: 300000us, load: 150000us, rounds: 18
set interactive ascpufreq governor
powersave cycle took457701us, sleep: 300000us, load: 150000us, rounds: 18
powersave cycle took462000us, sleep: 300000us, load: 150000us, rounds: 18
powersave cycle took457623us, sleep: 300000us, load: 150000us, rounds: 18
powersave cycle took461664us, sleep: 300000us, load: 150000us, rounds: 18
powersave cycle took458122us, sleep: 300000us, load: 150000us, rounds: 18
performance is at 91.21%
set performance ascpufreq governor
calibrating load of200000us, please wait...
calibrating with 24rounds
calibrating with 25rounds
calibrating with 25rounds
calibrating with 25rounds
calibration done
_round 4: doing 5cycles with 25 calculations for 200000us
avarage: 8000us,rps:125
performance cycletook 602273us, sleep: 400000us, load: 200000us, rounds: 25
performance cycletook 602022us, sleep: 400000us, load: 200000us, rounds: 25
performance cycletook 602541us, sleep: 400000us, load: 200000us, rounds: 25
performance cycletook 602642us, sleep: 400000us, load: 200000us, rounds: 25
performance cycletook 603079us, sleep: 400000us, load: 200000us, rounds: 25
set interactive ascpufreq governor
powersave cycle took616433us, sleep: 400000us, load: 200000us, rounds: 25
powersave cycle took613765us, sleep: 400000us, load: 200000us, rounds: 25
powersave cycle took616331us, sleep: 400000us, load: 200000us, rounds: 25
powersave cycle took614218us, sleep: 400000us, load: 200000us, rounds: 25
powersave cycle took615348us, sleep: 400000us, load: 200000us, rounds: 25
performance is at 94.10%
set performance ascpufreq governor
calibrating load of250000us, please wait...
calibrating with 30rounds
calibrating with 31rounds
calibrating with 31rounds
calibrating with 31rounds
calibration done
_round 5: doing 5cycles with 31 calculations for 250000us
avarage: 8064us,rps:124
performance cycletook 752050us, sleep: 500000us, load: 250000us, rounds: 31
performance cycletook 751701us, sleep: 500000us, load: 250000us, rounds: 31
performance cycletook 751966us, sleep: 500000us, load: 250000us, rounds: 31
performance cycletook 752029us, sleep: 500000us, load: 250000us, rounds: 31
performance cycletook 752338us, sleep: 500000us, load: 250000us, rounds: 31
set interactive ascpufreq governor
powersave cycle took768047us, sleep: 500000us, load: 250000us, rounds: 31
powersave cycle took763706us, sleep: 500000us, load: 250000us, rounds: 31
powersave cycle took766064us, sleep: 500000us, load: 250000us, rounds: 31
powersave cycle took763898us, sleep: 500000us, load: 250000us, rounds: 31
powersave cycle took765694us, sleep: 500000us, load: 250000us, rounds: 31
performance is at 94.93%
可见它的结果为：
Round 1 - <span style="color:#FF%
Round 2 - <span style="color:#FF%
Round 3 - <span style="color:#FF%
Round 4 - <span style="color:#FF%
Round 5 - <span style="color:#FF%
interactive为UI或者说IO更好的响应而设计，测试结果也显示它在性能方面的考量更加aggressive一些。
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