blktrace编译与使用

时间：2023-05-21

在对ssd性能调优过程中，有使用到blktrace，本文对blktrace做一个记录

文章目录

1、blktrace介绍2.blktrace aarch64移植3、使用4、实例5、数据分析6、blktrace分析ssd性能差的问题实例 1、blktrace介绍

我们首先需要知道提交到 block I/O层的每个I/O执行的具体操作，如下图所示

blktrace功能如下：

提供关于单个I/O的详细的block layer信息低开销内核跟踪机制（在I/O压力相对较大的情况下，对应用程序性能的影响不到2%）可配置：
①可以指定一个或多个物理设备或逻辑设备
②用户可选择事件-可以在事件获取和/或格式化输出时指定过滤器同时支持“实时”和“回放”跟踪

blktrace总体架构如下：

2.blktrace aarch64移植

下载：

git clone git://git.kernel.dk/blktrace.git

aarch64安装：

make cleanmake CC=aarch64-linux-gnu-gcc blktrace blkparsecd bttmake CC=aarch64-linux-gnu-gcc btt

此时将blktrace blkparse btt拷贝至开发板即可，注意相关内核需要打开

CONFIG_FTRACE=yCONFIG_BLK_DEV_IO_TRACE=y

3、使用

首先对blktrace，blkparse ，btt做个简单的介绍，blktrace负责采集，blkparse负责对采集的数据进行解析，而btt能够协助分析统计

blktrace选项如下，常用的使用有

-d dev #添加一个设备追踪-o file #指定输出文件的名字

root@a1000:~# blktrace --helpblktrace: unrecognized option '--help'Usage: blktrace-d | --dev=[ -r | --relay= ][ -o | --output=][ -D

| --output-dir=[ -w | --stopwatch=][ -a | --act-mask=][ -A | --set-mask=][ -b | --buffer-size][ -n | --num-sub-buffers=][ -l | --listen][ -h | --host=][ -p | --port=][ -s | --no-sendfile][ -I | --input-devs=][ -v | --version][ -V | --version] -d Use specified device、May also be given last after options -r Path to mounted debugfs, defaults to /sys/kernel/debug -o File(s) to send output to -D Directory to prepend to output file names -w Stop after defined time, in seconds -a only trace specified actions、See documentation -A Give trace mask as a single value、See documentation -b Sub buffer size in KiB (default 512) -n Number of sub buffers (default 4) -l Run in network listen mode (blktrace server) -h Run in network client mode, connecting to the given host -p Network port to use (default 8462) -s Make the network client NOT use sendfile() to transfer data -I Add devices found in -v Print program version info -V Print program version info

blkparse选项如下，常用的使用有

-i input #输入包含跟踪数据的文件-o output #输出文件。如果未给出，则输出为标准输出

| --input-directory= ][ -f | --format= ][ -F | --format-spec= ][ -h | --hash-by-name ][ -o | --output= ][ -O | --no-text-output ][ -q | --quiet ][ -s | --per-program-stats ][ -t | --track-ios ][ -w | --stopwatch= ][ -M | --no-msgs[ -v | --verbose ][ -V | --version ] -a only trace specified actions、See documentation -A Give trace mask as a single value、See documentation -b stdin read batching -d Output file、If specified, binary data is written to file -D Directory to prepend to input file names -f Output format、Customize the output format、The format field identifies can be found in the documentation -F Format specification、Can be found in the documentation -h Hash processes by name, not pid -i Input file containing trace data, or '-' for stdin -o Output file、If not given, output is stdout -O Do NOT output text data -q Quiet、Don't display any stats at the end of the trace -s Show per-program io statistics -t Track individual ios、Will tell you the time a request took to get queued, to get dispatched, and to get completed -w only parse data between the given time interval in seconds. If 'start' isn't given, blkparse defaults the start time to 0 -M Do not output messages to binary file -v More verbose for marginal errors -V Print program version info

btt选项如下，常用的使用有

-i input #输入文件

4、实例对/dev/nvme0n1p1进行采集，随后执行dd命令。

root@a1000:~# blktrace -d /dev/nvme0n1p1&[1] 418root@a1000:~# dd of=/dev/null if=/dev/nvme0n1p1 bs=1M count=512512+0 records in512+0 records out536870912 bytes (537 MB, 512 MiB) copied, 0.74305 s, 723 MB/sroot@a1000:~# kill -9 418[1]+ Killed blktrace -d /dev/nvme0n1p1

利用blkparse对blktrace采集的文件进行解析，其中-d 是输出二进制文件，方便btt分析，-o 是将blkparse解析的数据放入nvme_data中，可自行分析。

root@a1000:~# ls -lh nvme0n1p1.blktrace.0-rw-r--r-- 1 root root 8.0M Jan 18 17:10 nvme0n1p1.blktrace.0root@a1000:~# blkparse -i nvme0n1p1 -d nvme.blktrace.bin -o nvme_dataInput file nvme0n1p1.blktrace.0 addedBad magic 0

nvme_data原始数据内容如下：

btt解析nvme.blktrace.bin

root@a1000:~# btt -i nvme.blktrace.bin==================== All Devices ==================== ALL MIN AVG MAX N--------------- ------------- ------------- ------------- -----------Q2Q 0.000151718 0.000393516 0.009215535 2912Q2G 0.000002172 0.000002721 0.000030020 2912D2C 0.000366797 0.000482912 0.000821314 2911Q2C 0.000381274 0.000497561 0.000835603 2911==================== Device Overhead ==================== DEV | Q2G G2I Q2M I2D D2C---------- | --------- --------- --------- --------- --------- (259, 3) | 0.5470% 0.0000% 0.0000% 0.0000% 97.0557%---------- | --------- --------- --------- --------- --------- Overall | 0.5470% 0.0000% 0.0000% 0.0000% 97.0557%==================== Device Merge Information ==================== DEV | #Q #D Ratio | BLKmin BLKavg BLKmax Total---------- | -------- -------- ------- | -------- -------- -------- -------- (259, 3) | 2913 2912 1.0 | 256 255 256 745216==================== Device Q2Q Seek Information ==================== DEV | NSEEKS MEAN MEDIAN | MODE---------- | --------------- --------------- --------------- | --------------- (259, 3) | 2913 0.7 0 | 0(2912)---------- | --------------- --------------- --------------- | --------------- Overall | NSEEKS MEAN MEDIAN | MODE Average | 2913 0.7 0 | 0(2912)==================== Device D2D Seek Information ==================== DEV | NSEEKS MEAN MEDIAN | MODE---------- | --------------- --------------- --------------- | --------------- (259, 3) | 2912 0.7 0 | 0(2911)---------- | --------------- --------------- --------------- | --------------- Overall | NSEEKS MEAN MEDIAN | MODE Average | 2912 0.7 0 | 0(2911)==================== Plug Information ==================== DEV | # Plugs # Timer Us | % Time Q Plugged---------- | ---------- ---------- | ---------------- (259, 3) | 2912( 0) | 0.252751036% DEV | IOs/Unp IOs/Unp(to)---------- | ---------- ---------- (259, 2) | 0.0 0.0 (259, 3) | 1.0 0.0---------- | ---------- ---------- Overall | IOs/Unp IOs/Unp(to) Average | 1.0 0.0==================== Active Requests At Q Information ==================== DEV | Avg Reqs @ Q---------- | ------------- (259, 3) | 0.0==================== I/O Active Period Information ==================== DEV | # Live Avg、Act Avg、!Act % Live---------- | ---------- ------------- ------------- ------ (259, 2) | 0 0.000000000 0.000000000 0.00 (259, 3) | 1331 0.000716134 0.000144799 83.19---------- | ---------- ------------- ------------- ------ Total Sys | 1331 0.000716134 0.000144799 83.19# Total System# Total System : q activity 0.000006160 0.0 0.000006160 0.4 1.145925500 0.4 1.145925500 0.0# Total System : c activity 0.000537965 0.5 0.000537965 0.9 1.145756949 0.9 1.145756949 0.5# Per device# 259,3 : q activity 0.000006160 1.0 0.000006160 1.4 1.145925500 1.4 1.145925500 1.0# 259,3 : c activity 0.000537965 1.5 0.000537965 1.9 1.145756949 1.9 1.145756949 1.5# Per process# dd : q activity 0.000006160 2.0 0.000006160 2.4 1.145925500 2.4 1.145925500 2.0# dd : c activity# irq : q activity# irq : c activity 0.000537965 3.5 0.000537965 3.9 1.145756949 3.9 1.145756949 3.5

5、数据分析

第7个字段在上图中没有标出来，它表示操作类型，具体含义是：

”R” for Read, “W” for Write, “D” for block, “B” for Barrier operation。

第6个字段Event解释如下：

Q------->G------------>I--------->M------------------->D----------------------------->C |-Q time-|-Insert time-| |--------- merge time ------------|-merge with other IO| |----------------scheduler time time-------------------|---driver,adapter,storagetime--| |----------------------- await time in iostat output ----------------------------------|

其中：
Q2Q — time between requests sent to the block layer
Q2G — time from a block I/O is queued to the time it gets a request allocated for it
G2I — time from a request is allocated to the time it is Inserted into the device’s queue
Q2M — time from a block I/O is queued to the time it gets merged with an existing request
I2D — time from a request is inserted into the device’s queue to the time it is actually issued to the device
M2D — time from a block I/O is merged with an exiting request until the request is issued to the device
D2C — service time of the request by the device
Q2C — total time spent in the block layer for a request

blkparse解析出来的数据依旧是很难直接进行分析的，btt是对这些数据做一个总结。

6、blktrace分析ssd性能差的问题实例

linux nvme ssd性能降低分析

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