Workers CPU leak [epoll_wait,epoll_ctl]

[Valentin V. Bartenev]

On Wednesday 24 February 2016 09:17:01 vizl wrote:
> Hello, I have strange issuses with nginx workers. For some time after start
> Nginx I notice that some process of workers cause high load to CPU (
> principally sys CPU). 
> 
> At first I've got syscall traces from one of such process: 
> 
> futex(0x157d914, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0x157d910, {FUTEX_OP_SET, 0,
> FUTEX_OP_CMP_GT, 1}) = 1
> epoll_wait(38, {{EPOLLIN, {u32=7156096, u64=7156096}}}, 512, -1) = 1
> epoll_ctl(38, EPOLL_CTL_ADD, 178, {EPOLLOUT|EPOLLET, {u32=3888102096,
> u64=140028411886288}}) = 0
> epoll_wait(38, {{EPOLLOUT, {u32=3888102096, u64=140028411886288}}}, 512, -1)
> = 1
> epoll_ctl(38, EPOLL_CTL_DEL, 178, 7ffda2bc7f30) = 0
> futex(0x157d914, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0x157d910, {FUTEX_OP_SET, 0,
> FUTEX_OP_CMP_GT, 1}) = 1
> epoll_wait(38, {{EPOLLIN, {u32=7156096, u64=7156096}}}, 512, -1) = 1
> epoll_ctl(38, EPOLL_CTL_ADD, 178, {EPOLLOUT|EPOLLET, {u32=3888102096,
> u64=140028411886288}}) = 0
> epoll_wait(38, {{EPOLLOUT, {u32=3888102096, u64=140028411886288}}}, 512, -1)
> = 1
> epoll_ctl(38, EPOLL_CTL_DEL, 178, 7ffda2bc7f30) = 0
> futex(0x157d914, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0x157d910, {FUTEX_OP_SET, 0,
> FUTEX_OP_CMP_GT, 1}) = 1
> futex(0x157d8d0, FUTEX_WAKE_PRIVATE, 1) = 1
> 
> epoll_wait, epoll_ctl, futex are repeated circularly.
> 
> Then I've got lsof of process and see who owns of 38 file descriptor:
> 
> nginx   18862  www   38u  a_inode                0,9         0         6
> [eventpoll]
> 
> also I see several CLOSE_WAIT sockets
> 
> nginx   18862  www  101u     IPv4           85643376       0t0       TCP
> 154.59.82.194:http->105.107.179.210:24519 (CLOSE_WAIT)
> nginx   18862  www  133r      REG                8,3         0      4743
> /mnt/ssd1/wwwroot/71/7/27394667.mp4 (deleted)
> nginx   18862  www  178u     IPv4           86054929       0t0       TCP
> 154.59.82.194:http->5adc98ed.bb.sky.com:45665 (CLOSE_WAIT)
> nginx   18862  www  179r      REG                8,3         0      5098
> /mnt/ssd1/wwwroot/21/9/29603499.mp4 (deleted)
> 
> 
> Nginx has such version and modules:
> 
> nginx version: nginx/1.9.11
> built with OpenSSL 1.0.2f  28 Jan 2016
> TLS SNI support enabled
> configure arguments: --prefix=/usr --conf-path=/etc/nginx/nginx.conf
> --error-log-path=/var/log/nginx/error_log --pid-path=/run/nginx.pid
> --lock-path=/run/lock/nginx.lock --with-cc-opt=-I/usr/include
> --with-ld-opt=-L/usr/lib64 --http-log-path=/var/log/nginx/access_log
> --http-client-body-temp-path=/var/lib/nginx/tmp/client
> --http-proxy-temp-path=/var/lib/nginx/tmp/proxy
> --http-fastcgi-temp-path=/var/lib/nginx/tmp/fastcgi
> --http-scgi-temp-path=/var/lib/nginx/tmp/scgi
> --http-uwsgi-temp-path=/var/lib/nginx/tmp/uwsgi --with-file-aio --with-ipv6
> --with-pcre --with-threads --without-http_autoindex_module
> --without-http_fastcgi_module --without-http_geo_module
> --without-http_limit_req_module --without-http_limit_conn_module
> --without-http_memcached_module --without-http_uwsgi_module
> --with-http_flv_module --with-http_gzip_static_module --with-http_mp4_module
> --with-http_perl_module
> --add-module=external_module/headers-more-nginx-module-0.261
> --add-module=external_module/ngx_estreaming_module-0.01
> --add-module=external_module/ngx_slice_module-0.01 --with-http_ssl_module
> --without-mail_imap_module --without-mail_pop3_module
> --without-mail_smtp_module --user='www --group=www'
> 
> and using for video streaming.
> 
> Has anyone encountered such behavior ? Help please.
> 
[..]

Could you provide a minimal configuration that is causing problems
with debug log?  See: http://nginx.org/en/docs/debugging_log.html

  wbr, Valentin V. Bartenev