Linux performance testing and monitoring sar command_PHP tutorial

Linux performance testing and monitoring sar command

sar (System Activity Reporter system activity report) is currently one of the most comprehensive system performance analysis tools on Linux, which can be used from many aspects Report system activities, including: file reading and writing, system call usage, disk I/O, CPU efficiency, memory usage, process activities and IPC-related activities. This article mainly uses the CentOS6.3 x64 system as an example to introduce the sar command.

Common format of sar command

sar [options] [-A] [-o file] t [n]

where:

t is sampling Interval, n is the number of samples, and the default value is 1;

-o file means storing the command results in a file in binary format, and file is the file name.

options are command line options. Commonly used options for the sar command are as follows:

-A: The sum of all reports

-u: Output CPU usage statistics

-v: Output statistics about inodes, files, and other kernel tables

-d: Output activity information for each block device

- r: Output statistical information of memory and swap space

-b: Display statistical information of I/O and transfer rate

-a: File reading and writing status

-c : Output process statistics, number of processes created per second

-R: Output statistics of memory pages

-y: Terminal device activity

-w: Output System exchange activity information

1. CPU resource monitoring

For example, sample once every 10 seconds, sample 3 times continuously, observe the CPU usage, and store the sampling results in binary form into the current In the file test in the directory, you need to type the following command:

sar -u -o test 10 3

The screen displays as follows:

17:06:16 CPU %user %nice %system %iowait %steal %idle

17:06:26 all 0.00 0.00 0.20 0.00 0.00 99.80

17:06:36 all 0.00 0.00 0.20 0.00 0.00 99.8 0

17:06:46 all 0.00 0.00 0.10 0.00 0.00 99.90

Average: all 0.00 0.00 0.17 0.00 0.00 99.83

Output item description:

C PU: all means statistics Information is averaged across all CPUs.

%user: Displays the percentage of total CPU time used by running at the user level (application).

%nice: Displayed at the user level, the percentage of the total CPU time used for nice operations.

%system: The percentage of total CPU time used by running at the kernel level.

%iowait: Displays the percentage of total CPU time spent waiting for I/O operations.

%steal: The percentage of virtual CPU that the hypervisor is waiting for to service another virtual process.

%idle: Displays the percentage of CPU idle time occupied by the total CPU time.

1. If the value of %iowait is too high, it means that the hard disk has an I/O bottleneck

2. If the value of %idle is high but the system response is slow, it may be that the CPU is waiting to allocate memory. , at this time, the memory capacity should be increased

3. If the value of %idle continues to be lower than 1, the system's CPU processing capability is relatively low, indicating that the most important resource in the system is the CPU.

If you want to view the contents of the binary file test, you need to type the following sar command:

sar -u -f test

2. Inode, file and other kernel table monitoring

For example, to sample every 10 seconds for 3 consecutive times to observe the status of the core table, type the following command:

sar -v 10 3

The screen displays as follows :

17:10:49 dentunusd file-nr inode-nr pty-nr

17:10:59 6301 5664 12037 4

17:11:09 6301 5664 12037 4

17:11:19 6301 5664 12037 4

Average: 6301 5664 12037 4

Output description:

dentunusd: directory cache The number of unused entries in

file-nr: the number of file handles used

inode-nr: the number of inode handles used

pty-nr: Number of pty used

3. Memory and swap space monitoring

For example, sample every 10 seconds, sample 3 times continuously, monitor memory paging:

sar -r 10 3

The screen displays as follows:

Output item description:

kbmemfree: This value is the same as in the free command The free value is basically the same, so it does not include the buffer and cache space.

kbmemused: This value is basically the same as the used value in the free command, so it includes the buffer and cache space.

%memused: This value is a percentage of kbmemused and total memory (excluding swap).

kbbuffers and kbcached: These two values ​​are the buffer and cache in the free command.

kbcommit: Guarantee the memory required by the current system, that is, the memory (RAM swap) required to ensure no overflow.

%commit: This value is a percentage of kbcommit and the total memory (including swap).

4. Memory paging monitoring

For example, sample every 10 seconds, sample 3 times continuously, monitor memory paging:

sar -B 10 3

The screen displays as follows:

Output item description:

pgpgin/s: Indicates the number of bytes (KB) replaced from disk or SWAP to memory per second

pgpgout/s: Indicates the number of bytes replaced from memory to disk or SWAP per second (KB)

fault/s: The number of page faults generated by the system per second, that is, the number of primary and secondary page faults Sum of missing pages (major minor)

majflt/s: The number of major missing pages generated per second.

pgfree/s: The number of pages placed in the idle queue per second

pgscank/s: The number of pages scanned by kswapd per second

pgscand/s: The number of pages directly scanned per second

pgsteal/s: per second The number of pages cleared from the cache to meet memory requirements

%vmeff: the percentage of pages cleared per second (pgsteal) to the total scanned pages (pgscank pgscand)

5. I /O and transfer rate monitoring

For example, to sample every 10 seconds, sample 3 times continuously, and report buffer usage, type the following command:

sar -b 10 3

The screen displays as follows:

18:51:05 tps rtps wtps bread/s bwrtn/s

18:51:15 0.00 0.00 0.00 0.00 0.00

18:51:25 1.92 0.00 1.92 0.00 22.65

18:51:35 0.00 0.00 0.00 0.00 0.00

Average: 0.64 0.00 0.64 0.00 7.59

Output item description:

tps: The total amount of I/O transfers from the physical device per second

rtps: The total amount of data read from the physical device per second

wtps: per second The total amount of data written to the physical device

bread/s: The amount of data read from the physical device per second, in blocks/s

bwrtn/s: The amount of data written to the physical device per second The amount of data written by the physical device, in blocks/s

6. Process queue length and average load status monitoring

For example, sample every 10 seconds, sample 3 times continuously, monitor the process Queue length and average load status:

sar -q 10 3

The screen displays as follows:

19:25:50 runq-sz plist-sz ldavg-1 ldavg- 5 ldavg-15

19:26:00 0 259 0.00 0.00 0.00

19:26:10 0 259 0.00 0.00 0.00

19:26:20 0 259 0.00 0.00 0.00

Average: 0 259 0.00 0.00 0.00

Output item description:

runq-sz: The length of the run queue (number of processes waiting to run)

plist-sz: The number of processes and threads in the process list

ldavg-1: System load average in the last minute

ldavg- 5: System load average in the past 5 minutes

ldavg-15: System load average in the past 15 minutes

7. System exchange activity information monitoring

For example, every 10 seconds Sampling once, sampling 3 times continuously, the monitoring system exchanges activity information:

sar -W 10 3

The screen displays as follows:

19:39:50 pswpin/s pswpout /s

19:40:00 0.00 0.00

19:40:10 0.00 0.00

19:40:20 0.00 0.00

Average: 0.00 0.00

Output item description:

pswpin/s: The number of swap pages swapped in by the system per second

pswpout/s: The number of swap pages swapped out by the system per second Number of swap pages

8. Device usage monitoring

For example, to sample every 10 seconds for 3 consecutive times to report device usage, type the following command:

# sar -d 10 3 –p

The screen displays as follows:

17:45:54DEVtpsrd_sec/swr_sec/savgrq-szavgqu-szawaitsvctm%util

17 :46:04scd00.000.000.000.000.000.000.000.00

17:46:04sda0.000.000.000.000.000.000.000.00

17:46:04vg_livedvd -lv_root0.000.000.000.000.000.000 .000.00

17:46:04vg_livedvd-lv_swap0.000.000.000.000.000.000.000.00

Among them:

The parameter -p can print out the disk device names such as sda, hdc and so on. , if the parameter -p is not used, the device node may be dev8-0, dev22-0

tps: the number of I/Os from the physical disk per second. Multiple logical requests will be merged into one I/O O disk request, the size of a transfer is uncertain.
rd_sec/s: The number of sectors read per second.

wr_sec/s: The number of sectors written per second.

avgrq-sz: Average data size (sectors) of each device I/O operation.

avgqu-sz: Average length of disk request queue.

await: Request disk from From the operation until the system completes processing, the average time consumed for each request, including the request queue waiting time, the unit is milliseconds (1 second = 1000 milliseconds).

svctm: The average time the system takes to process each request, excluding The time spent in the request queue.

%util: The percentage of I/O requests in the CPU. The larger the ratio, the more saturated it is.

1. When the value of avgqu-sz is low , the equipment utilization rate is higher.

2. When the value of %util is close to 1%, it means that the device bandwidth is full.

To determine system bottlenecks, sometimes you need to combine several sar command options

If you suspect that there is a CPU bottleneck, you can use sar -u and sar -q to check

If you suspect If there is a bottleneck in the memory, you can use sar -B, sar -r and sar -W to check

If you suspect that there is a bottleneck in I/O, you can use sar -b, sar -u and sar -d to check