KPTI熔毁Linux内核修复对性能的影响

Question

因此，我最近(2018年1月初)收到了我的Fedora 26笔记本电脑的内核更新，其中包括修正熔毁虫熔毁虫的KPTI内核修复。我听到了很多关于这些补丁对Linux系统的影响的猜测；的确，英特尔似乎相信皇帝的衣冠楚楚。从链接中可以看出，业内的一些消息来源(尤其是苹果、微软、亚马逊和谷歌)声称，影响可以忽略不计--参见此链接。其他的索赔巨大影响。

我不满足于我在新闻报道中看到的混乱，我想知道，“我的机器将受到什么真正的影响？”我问。理论上，CPU绑定进程的影响可以忽略不计，而执行大量系统调用(例如磁盘或网络i/o )的进程将受到更多的影响。

我在下面回答自己。

我还没有看到更多现代处理器的基准；这将是非常有趣的，因为我听说过“...the较新的处理器不会有巨大的损失”是那些处理器，怎么不是-巨大不是很大？我有一个较老的联想Thinkpad T430S与英特尔i5-3210m双核(每个核心2个线程)处理器。关于熔毁及其修复问题，这是现代的还是不现代的？据微软称，“.(它)说，2015年或更早运行Windows 7、8和10处理器的消费类设备更有可能出现减速。”但英特尔的自己的基准测试似乎没有显示出2015和2017年处理器之间的区别。

Answer 1

在启动新内核之前，我想得到一些真实的数字。我将内核从4.14.8升级到4.14.11。后者包括KPTI修复崩溃漏洞。我有一个较老的联想Thinkpad T430S与英特尔i5-3210m双核(每个核心2个线程)处理器。结果很有趣，所以我想我应该把它们张贴在这里。

我执行了三个基准：

• AIM9是在https://sourceforge.net/projects/aimbench/files/aim-suite9/Initial%20release/s9110.tar.Z/download .This基准测试中提供的，但对于测试系统的基本操作(包括整数、浮点、文件操作、消息传递等)似乎相当全面。
• 编译x86_64 gcc编译器。
• 运行古老的bonnie++基准测试版本1.97。

结果如下。除了一些令人惊讶的值(辅助循环/秒和目录操作AIM9基准，块顺序输出bonnie++基准都显示了更好的性能)，该系统似乎受到了一些打击。我发现gcc编译相当有趣，因为编译同时涉及很多文件i/o和CPU操作。这些事情和我经常在机器上做的任务很相似。无论如何，这3组基准似乎都在一件事上达成了一致:自从安装KPTI熔毁修复内核以来，我的系统总体上受到了可衡量的打击--甚至是整数和浮点操作。我现在要花172分钟才能完成gcc的一篇160分钟的汇编。真扫兴。

AIM9 benchmark
AIM Independent Resource Benchmark - Suite IX v1.1, January 22, 1996
Copyright (c) 1996 - 2001 Caldera International, Inc.
All Rights Reserved

BEFORE:
Machine's name                                    : rodin
Machine's configuration                           : kernel_4.14.8-200
Number of seconds to run each test [2 to 1000]    : 10
Path to disk files                                : /var/tmp/aim9

AFTER:
Machine's name                                    : rodin
Machine's configuration                           : kernel_4.14.11-200
Number of seconds to run each test [2 to 1000]    : 10
Path to disk files                                : /var/tmp/aim9

注意: AIM9基准测试有一个错误，在编译时，不允许完成其中一个测试。为了让它运行，我不得不更改creat-clo.c上的第97行，如下所示：

static int sigcount;           /* count of signals */

对此：

volatile static int sigcount;           /* count of signals */

以下是我的基准测试结果：

AIM9 Benchmark
         BEFORE        AFTER Percent Change   Description
01      1.996 M      1.929 M   -3.34 Thousand Double Precision Additions/second
02      1.980 M      1.945 M   -1.75 Thousand Single Precision Additions/second
03      8.559 M      8.259 M   -3.50 Thousand Long Integer Additions/second
04      8.592 M      8.280 M   -3.63 Thousand Integer Additions/second
05      8.599 M      8.268 M   -3.85 Thousand Short Integer Additions/second
06    205400.00    190400.00   -7.30 File Creations and Closes/second
07    552330.00    384665.33  -30.35 System Allocations & Pages/second
08      2.844 M      1.373 M  -51.71 System Memory Allocations/second
09     75.980 M     74.623 M   -1.78 Non-local gotos/second
10      1.131 M    651400.00  -42.43 Signal Traps/second
11       855.64       787.71   -7.93 Program Loads/second
12      3246.75      3846.15   18.46 Task Creations/second
13    166307.40    154135.80   -7.31 Link/Unlink Pairs/second
14    504839.16    369664.00  -26.77 Random Disk Reads (K)/second
15    451072.00    339628.37  -24.70 Random Disk Writes (K)/second
16      3.285 M      1.765 M  -46.24 Sequential Disk Reads (K)/second
17    698880.00    598528.00  -14.35 Sequential Disk Writes (K)/second
18    537088.00    431616.00  -19.63 Disk Copies (K)/second
19       115.78       116.58     .69 Sync Random Disk Writes (K)/second
20       116.42       114.75   -1.43 Sync Sequential Disk Writes (K)/second
21       116.05       114.90    -.99 Sync Disk Copies (K)/second
22     79020.00     73711.29   -6.71 Directory Searches/second
23    311100.00    299400.00   -3.76 Thousand Double Precision Divides/second
24    316483.52    305694.31   -3.40 Thousand Single Precision Divides/second
25    105284.72    101688.31   -3.41 Thousand Long Integer Divides/second
26    294660.00    286470.00   -2.77 Thousand Integer Divides/second
27    290700.00    282420.00   -2.84 Thousand Short Integer Divides/second
28    424.140 M    407.756 M   -3.86 Function Calls (no arguments)/second
29    462.336 M    448.460 M   -3.00 Function Calls (1 argument)/second
30    485.198 M    472.115 M   -2.69 Function Calls (2 arguments)/second
31    236.441 M    226.969 M   -4.00 Function Calls (15 arguments)/second
32       195.30       186.63   -4.43 Integer Sieves/second
33      1.202 M      1.160 M   -3.48 Thousand Double Precision Multiplies/second
34      1.204 M      1.166 M   -3.18 Thousand Single Precision Multiplies/second
35      1.396 M      1.359 M   -2.69 Thousand Long Integer Multiplies/second
36      1.396 M      1.357 M   -2.83 Thousand Integer Multiplies/second
37      1.365 M      1.327 M   -2.78 Thousand Short Integer Multiplies/second
38    554540.00    538080.00   -2.96 Numeric Functions/second
39      1.614 M      1.561 M   -3.28 Zeros Found/second
40      2.513 M      2.431 M   -3.28 Trigonometric Functions/second
41     18.605 M     17.861 M   -4.00 Point Transformations/second
42      3880.00      3766.00   -2.93 Linear Systems Solved/second
43     28060.00     26980.00   -3.84 String Manipulations/second
44     14.751 M     14.373 M   -2.55 Dynamic Memory Operations/second
46      5277.00      5121.00   -2.95 Sort Operations/second
47      4231.00     10771.00  154.57 Auxiliary Loops/second
48      2.828 M      2.900 M    2.54 Directory Operations/second
49       137.36       156.70   14.07 Shell Scripts/second
50       137.16       157.64   14.93 Shell Scripts/second
51       137.60       161.90   17.65 Shell Scripts/second
52     44.497 M     42.774 M   -3.87 Series Evaluations/second
53      1.092 M    607030.00  -44.43 Shared Memory Operations/second
56      1.318 M    825670.00  -37.38 FIFO Messages/second
57    922370.00    664690.00  -27.93 Stream Pipe Messages/second
58    866290.00    632950.00  -26.93 DataGram Pipe Messages/second
59      1.922 M      1.038 M  -45.96 Pipe Messages/second
60  19725.935 M  18947.483 M   -3.94 Memory to Memory Copy/second

=========================================================================================================
GCC compile, both "configure" and "make"
Results summary::
configure: 38% real slowdown

make (x86_64 only): 7.7% real slowdown, 5.5% user CPU slowdown

    BEFORE                                         AFTER
time ../gcc-7.2.0/configure --disable-multilib | time ../gcc-7.2.0/configure --disable-multilib
 ...                                           | ...   
configure: creating ./config.status            | configure: creating ./config.status
config.status: creating Makefile               | config.status: creating Makefile
                                               |
real    0m2.467s                               | real    0m3.420s      
user    0m1.835s                               | user    0m1.936s      
sys     0m1.108s                               | sys     0m1.295s      
                                               |
time make                                      | time make
...                                            | ...     
real    160m8.766s                             | real    172m28.158s
user    152m11.430s                            | user    163m34.790s      
sys     6m41.507s                              | sys     7m5.214s     

=========================================================================================================
BONNIE++
Version: 1.97
See https://www.coker.com.au/bonnie++/experimental/ . This version was provided by my Fedora distribution.

Run using: bonnie++ -n 1024

Sample results:
                                BEFORE          AFTER           % change from before
Sequential Output, per char     1115 K/s        890 K/s         -20
Sequential Output, block        358891 K/s      461208 K/s      +28
Sequential Input, per char      4181 K/s        1989 K/s        -52
Sequential Input, block         515347 K/s      521646 K/s      -1,2
Random Seeks                    5651 /s         5221 /s         -7.6
Sequential Create, Create       41855 /s        40751 /s        -2.74
                   Read         741945 /s       624554 /s       -15.8
                   Delete       79832 / s       78340 /s        -1.9
Random Create,     Create       41198 /s        41003 /s        -0.47
                   Read         741945 /s       719494 /s       -3.02
                   Delete       61154 /s        60698 /s        -0.74

邦妮的调查结果可在以下网址查阅：

以前：https://bintray.com/greygnome/generic/download_档案?档案_path=bon_结果_在此之前_kpti.html

后：https://bintray.com/greygnome/generic/download_档案?档案_path=bon_结果_之后_kpti.html