Bug #72322 [Com]: High sys CPU usage

Edit report at https://bugs.php.net/bug.php?id=72322&edit=1 ID: 72322 Comment by: jai at vidyamantra dot com Reported by: jai at vidyamantra dot com Summary: High sys CPU usage Status: Re-Opened Type: Bug Package: Performance problem Operating System: Centos 6.8 x64 PHP Version: 7.0.7 Block user comment: N Private report: N New Comment: It has been two days since when we modified following kernel values. vm.extra_free_kbytes vm.min_free_kbytes Since then, we are not facing this problem. It appears the problem is with the way how PHP7 allocates or uses memory. We were able to reproduce this problem on two entirely different and isolated production servers that had no problem with php5 but this problem started within few hours after we upgraded to PHP7. Our servers have 256GB of RAM and this issue appears when free memory is low. Clearing system buffers/cache (echo 3 > /proc/sys/vm/drop_caches) always fixes this problem but Linux gradually starts caching files from disk and free memory starts dropping. Previous Comments: ------------------------------------------------------------------------ [2016-12-25 04:22:19] php-bugs at lists dot php dot net No feedback was provided. The bug is being suspended because we assume that you are no longer experiencing the problem. If this is not the case and you are able to provide the information that was requested earlier, please do so and change the status of the bug back to "Re-Opened". Thank you. ------------------------------------------------------------------------ [2016-12-20 07:33:31] jai at vidyamantra dot com Tested on version 7.0.10 and problem is still present. It happens more often when system memory is near full (swap still empty), for e.g. system has 256GB of RAM and this happens when about only 10GB of RAM is used. At this stage, sys time increase significantly. ------------------------------------------------------------------------ [2016-12-17 14:51:26] nikic@php.net Do you still experience this problem with a current version of PHP 7? I'd assume the issue is due to huge pages (see https://bugs.php.net/bug.php?id=70984), which are no longer enabled by default. ------------------------------------------------------------------------ [2016-06-03 06:58:47] jai at vidyamantra dot com Description: ------------ Upgrade to php 7 and saw high CPU usage. http://serverfault.com/q/780555/126826 (CPU graphs and sar output). ==== PHP 7 ==== % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 31.24 0.000973 1 1204 munmap 15.25 0.000475 0 1523 3 open 12.52 0.000390 0 4012 216 lstat 7.70 0.000240 0 1363 mmap 5.81 0.000181 0 1528 close 5.36 0.000167 1 219 getdents 5.01 0.000156 0 1618 stat 4.33 0.000135 0 1433 535 access 3.69 0.000115 0 3256 fstat 2.47 0.000077 0 547 write 1.67 0.000052 0 224 uname 1.22 0.000038 0 276 sendto 0.87 0.000027 0 638 read 0.83 0.000026 0 752 flock 0.58 0.000018 0 760 poll ==== PHP 5 ==== % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 23.32 0.001103 5 206 sendto 17.45 0.000825 1 1650 getdents 14.95 0.000707 0 4638 651 stat 10.59 0.000501 0 3181 1708 access 7.27 0.000344 0 4918 172 lstat 6.07 0.000287 0 2391 3 open 4.76 0.000225 1 314 poll 3.66 0.000173 0 1526 munmap 2.56 0.000121 0 4633 fstat 2.11 0.000100 0 1704 mmap 1.54 0.000073 1 97 rename 1.40 0.000066 0 923 2 lseek 1.08 0.000051 0 2395 close 0.80 0.000038 0 562 49 ioctl 0.68 0.000032 0 831 read 0.57 0.000027 0 406 write 0.34 0.000016 0 141 mprotect ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=72322&edit=1