Recently I have upgraded to the mainline Debian 10 backport kernel. This morning I've noticed that the web server is very slow, and inspection showed 100% CPU usage by php7.4-fpm:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
13901 www-data 20 0 461632 240612 91188 R 100.0 0.5 37:09.65 php-fpm7.4
16105 root 20 0 154088 101800 19280 R 100.0 0.2 0:48.18 php
13792 www-data 20 0 460844 240328 91512 R 100.0 0.5 37:31.51 php-fpm7.4
13948 www-data 20 0 463308 243644 94548 R 100.0 0.5 37:16.08 php-fpm7.4
16040 username 20 0 11708 10196 4612 R 100.0 0.0 1:02.09 imap
13752 www-data 20 0 467348 247620 93176 R 100.0 0.5 38:39.73 php-fpm7.4
739 clamav 20 0 2725056 2.3g 11028 S 100.0 4.8 52:25.38 clamd
13796 www-data 20 0 464888 247260 95524 R 100.0 0.5 39:00.51 php-fpm7.4
The traced php7.4-fpm process appears to be looping and executing only the mremap() system call:
mremap(0x7f48cb600000, 13074432, 13078528, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13078528, 13082624, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13082624, 13086720, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13086720, 13090816, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13090816, 13094912, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13094912, 13099008, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13099008, 13103104, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13103104, 13107200, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13107200, 13111296, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13111296, 13115392, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13115392, 13119488, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13119488, 13123584, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13123584, 13127680, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13127680, 13131776, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13131776, 13135872, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13135872, 13139968, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13139968, 13144064, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13144064, 13148160, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13148160, 13152256, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13152256, 13156352, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13156352, 13160448, 0) = 0x7f48cb600000
mremap(0x7f48cb600000, 13160448, 13164544, 0) = 0x7f48cb600000
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Version of php7.4-fpm is 1:7.4.33-5+0~20230409.78+debian10~1.gbpa1ea7f alongside PHP packages from https://packages.sury.org/php/ buster, updated Apr/12/2023.
No change in configuration was made.
Rebooting into 4.19.0-23-amd64 kernel 4.19.269-1 did not fix the issue.
ii linux-image-4.19.0-23-amd64 4.19.269-1
There was no change of the configuration in the last weak AFAICR.
I tried to boot into the 4.19.0-23 kernel, expecting that it could be the problem with BPO 5.10.127-2 kernel.
However, the 100% CPU usage by the fpm7.4-fpm and very slow web remained.
