Reasons why a php process cpu % nice is very high

1. symptom Description: 1. the CPU usage of % user and % sys is not high, but % nice occupies a large amount of CPU resources, with a maximum CPU usage of more than 60%; 2. In ps-elf, PRI is 90, NI is 10, and top is 30 and NI10. Question: Why is the priority value in ps different from that in top? PR in top is: Thepriorityofthe

1. symptom Description: 1. the CPU usage of % user and % sys is not high, but % nice occupies a large amount of CPU resources, with a maximum CPU usage of more than 60%; 2. In ps-elf, the PRI value is 90, the NI value is 10, and the top value is 30 and NI 10. Question: Why are the priority values in ps different from those in top? PR in top is: The priority of

1. symptom description:

1. CPU usage of % user and % sys is not high, but % nice occupies a large amount of CPU resources, with a maximum CPU usage of more than 60%; 2. In ps-elf, PRI is 90, NI is 10, and prvalue is 30 and NI 10 is displayed on top;

Problem:Why is the priority value in ps different from that in top?
PR in top is: The priority of the task (value range:-20 Highest, 19 lowest)
In ps, PRI is: realtime priority (calculated based on nice () and setpriority (). The Static priority value is 1-99, and Dynamic priority has not been understood yet)

3. sar information collection

CPU：Linux 2.6.32-279.el6.x86_64 (web2.17173ops.com) 05/09/2014 _x86_64_ (8 CPU)12:00:04 AM CPU %user %nice %system %iowait %steal %idle12:01:01 AM all 0.39 26.67 1.84 30.15 0.00 40.9512:02:03 AM all 0.30 24.07 2.74 30.10 0.00 42.8012:03:01 AM all 0.27 23.61 1.65 34.48 0.00 40.0012:04:02 AM all 0.26 23.37 1.96 34.87 0.00 39.5412:05:04 AM all 0.31 24.08 3.74 36.66 0.00 35.2112:06:02 AM all 0.43 21.96 2.09 34.93 0.00 40.5912:07:16 AM all 0.25 23.66 2.07 59.63 0.00 14.3812:08:02 AM all 0.33 30.21 2.01 36.88 0.00 30.57

Ii. server hardware/software:

Product Name: PowerEdge R410CPU：Intel(R) Xeon(R) CPU E5606 @ 2.13GHzMemory：24GB 4*6OS：Red Hat Enterprise Linux Server release 6.3 (Santiago)Web server：nginx version: nginx/1.4.4CGI server：php-5.3.21

Iii. problem determination:
1. NICE resources are generally generated by user-side control;
2. Unless a large number of sleep functions are used in the program or nice functions are called, the user-defined priority level is given, but the general program will not be so abnormal;

4. troubleshooting process:
1. Traditionally, it is a problem of program development. It is a waste of time to find words like sleep and nice in the code;
2. ps-elf | grep master, found that the startup time of php-fpm is inconsistent, some are, some are. If it is defined by crontab, the time will certainly not be so inconsistent;
3. Search for/etc/crontab. No scheduled task is defined in the file;
4. The scheduled task of RHEL6 is taken over by anacrontab. anacrontab is a supplement to crontab. The content is as follows: (The problem lies in the red + note line below)

# Cat/etc/anacrontab #/etc/anacrontab: configuration file for anacron # See anacron (8) and anacrontab (5) for details. SHELL =/bin/shPATH =/sbin:/bin:/usr/sbin: /usr/binMAILTO = root # the maximal random delay added to the base delay of the jobsRANDOM_DELAY = 45 # the jobs will be started during the following hours onlySTART_HOURS_RANGE = 3-22 # period in days delay in minutes job-identifier command1 5 cron. daily nice run-parts/etc/cron. daily # log cutting timing task in this 7 25 cron. weekly nice run-parts/etc/cron. weekly @ monthly 45 cron. monthly nice run-parts/etc/cron. monthly

5. Thinking and optimization:
1. It is not recommended to use anacrontab on the server and continue to use crontab; (this problem does not exist in RHEL5 );
2. In fact, the use of nice commands by anacrontab does not cause any problems, mainly because it works with restart in the php-fpm STARTUP script;
3. If php-fpm uses reload or kill-USR2, nice does not take effect, and the priority level of the original PID is used. Because we certainly won't bring nice when starting php-fpm manually.

Original article address: explanation of the reason why the cpu % nice of a php process is very high. Thank you for sharing it with the original author.