# Gzip causing high cpu load for streaming traffic **URL:** \ **Category:** NGINX\ **Created:** [January 8, 2011, 2:40am UTC](https://www.ruby-forum.com/t/gzip-causing-high-cpu-load-for-streaming-traffic/201476 "2011-01-08T02:40:58Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![luislavena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/0ea827/32.png) [@luislavena](https://www.ruby-forum.com/u/luislavena)\ **Post date:** [January 8, 2011, 2:40am UTC](https://www.ruby-forum.com/t/gzip-causing-high-cpu-load-for-streaming-traffic/201476/1 "2011-01-08T02:40:58Z")
Ok this is weird I noticed tonight high CPU load on two out of three of our stream servers, which are serving mp4 and flv via the pseudo streaming modules. After investigating the differences between the two high CPU boxes and the one low CPU machine the only notable difference was that on the two high CPU boxes the config was including our standard gzip options:- ```auto gzip on; gzip_static on; gzip_http_version 1.1; gzip_vary on; gzip_comp_level 6; gzip_proxied any; gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript; # make sure gzip does not lose large gzipped js or css files gzip_buffers 16 8k; # Disable gzip for certain browsers. gzip_disable "MSIE [1-6].(?!.*SV1)"; ``` Now as you can see the types is set to text based types so .mp4 and .flv files really shouldn’t be touched, so I looked else where. After much looking I really couldn’t find any significant differences so I added the include of the above to the low CPU machine. Sure enough the CPU instantly jumped up with each nginx process using 20-40% cpu instead of 0-2% it was before the reload. Still not convinced and after double checking the gzip config to confirm it really shouldn’t be going anywhere near the streaming content I added gzip off and gzip\_static off to the \*.mp4 and \*.flv locations in the config on the high CPU machine and reloaded. An hour or two later ( time for the existing users streams to finish ) and the CPU load has already dropped to the very low values I expect from nginx for the connection load on the machine e.g. 0 - 2% per nginx process instead of the 40-90% I was seeing. Just to confirm I checked the network load and connected users and sure enough the actual connections and bandwidth is still the same so the machine is still under the same amount of connection load as before just with significantly lower CPU. So what’s going on? Have I missed something totally obvious? Or is there a nasty bug which means when gzip is enabled in this manner it causes significant processing overhead for items its not even meant to be processing? In case its relavent our main http block includes: ```auto include mime.types; default_type application/octet-stream; ``` The current streaming bocks, which include the workaround (turning gzip off) are:- ```auto # Actual Streaming location ~ /streaming/(.*\.mp4)$ { # Fix strange CPU usage caused by gzip gzip off; gzip_static off; limit_rate_after 10m; limit_rate 400k; alias /streaming/$1; internal; mp4; } location ~ /streaming/(.*\.flv)$ { # Fix strange CPU usage caused by gzip gzip off; gzip_static off; limit_rate_after 10m; limit_rate 400k; alias /streaming/$1; internal; flv; } ``` Posted at Nginx Forum: > **[gzip causing high cpu load for streaming traffic](https://forum.nginx.org/read.php?2,164484,164484#msg-164484)** > > Ok this is weird I noticed tonight high CPU load on two out of three of our stream servers, which are serving mp4 and flv via the pseudo streaming modules. After investigating the differences between the two high CPU boxes and the one low CPU machine... ---
**Author:** ![steveh](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/5fc32e/32.png) [@steveh](https://www.ruby-forum.com/u/steveh)\ **Post date:** [January 8, 2011, 3:34am UTC](https://www.ruby-forum.com/t/gzip-causing-high-cpu-load-for-streaming-traffic/201476/2 "2011-01-08T03:34:18Z")
Hello! On Fri, Jan 07, 2011 at 08:39:52PM -0500, steveh wrote: > gzip\_http\_version 1.1; > [/code] > gzip off and gzip\_static off to the \*.mp4 and \*.flv locations in the > > So what’s going on? Have I missed something totally obvious? Or is there > a nasty bug which means when gzip is enabled in this manner it causes > significant processing overhead for items its not even meant to be > processing? Working with “gzip\_static on;” implies extra open() syscall per request (it work’s based on .gz file presense, not gzip\_types) and isn’t recommended unless actually used. It shouldn’t make any difference with flv handler activated though (flv disables general content handlers and gzip\_static in particular). Most likely the same applies to mp4. Working with “gzip on;” implies extra check for content-type per request (and some minimal checks during response sending). This shouldn’t cause much load. > # Actual Streaming > > } > flv; > } Could you please check if it’s gzip or gzip\_static which causes high cpu usage? Also, could you please provide some more details about nginx you’re using? I.e. nginx -V output, please. Maxim D. ---
**Author:** ![steveh](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/5fc32e/32.png) [@steveh](https://www.ruby-forum.com/u/steveh)\ **Post date:** [January 8, 2011, 3:52am UTC](https://www.ruby-forum.com/t/gzip-causing-high-cpu-load-for-streaming-traffic/201476/3 "2011-01-08T03:52:27Z")
Ok tested without gzip\_static off, no change, commenting out the gzip off however and CPU usage starts to climb within seconds of a reload so its definitely gzip causing. Posted at Nginx Forum: > **[Re: gzip causing high cpu load for streaming traffic](https://forum.nginx.org/read.php?2,164484,164493#msg-164493)** > > Ok this is weird I noticed tonight high CPU load on two out of three of our stream servers, which are serving mp4 and flv via the pseudo streaming modules. After investigating the differences between the two high CPU boxes and the one low CPU machine... ---
**Author:** ![steveh](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/5fc32e/32.png) [@steveh](https://www.ruby-forum.com/u/steveh)\ **Post date:** [January 8, 2011, 3:54am UTC](https://www.ruby-forum.com/t/gzip-causing-high-cpu-load-for-streaming-traffic/201476/4 "2011-01-08T03:54:57Z")
Version info, both which exhibit this behaviour:- nginx version: nginx/0.8.53 TLS SNI support enabled configure arguments: --prefix=/usr/local/etc/nginx --with-cc-opt=‘-I /usr/local/include’ --with-ld-opt=‘-L /usr/local/lib’ –conf-path=/usr/local/etc/nginx/nginx.conf –sbin-path=/usr/local/sbin/nginx --pid-path=/var/run/nginx.pid –error-log-path=/var/log/nginx-error.log --user=www --group=www –with-file-aio –http-client-body-temp-path=/var/tmp/nginx/client\_body\_temp –http-fastcgi-temp-path=/var/tmp/nginx/fastcgi\_temp –http-proxy-temp-path=/var/tmp/nginx/proxy\_temp –http-scgi-temp-path=/var/tmp/nginx/scgi\_temp –http-uwsgi-temp-path=/var/tmp/nginx/uwsgi\_temp –http-log-path=/var/log/nginx-access.log --with-http\_flv\_module –with-http\_geoip\_module --with-http\_gzip\_static\_module –add-module=/usr/ports/www/nginx-devel/work/nginx\_mod\_h264\_streaming-2.2.7 –with-http\_realip\_module --with-http\_ssl\_module –with-http\_stub\_status\_module --with-pcre –add-module=/usr/ports/www/nginx-devel/work/passenger-3.0.0/ext/nginx nginx version: nginx/0.8.49 configure arguments: --prefix=/usr/local/etc/nginx --with-cc-opt=‘-I /usr/local/include’ --with-ld-opt=‘-L /usr/local/lib’ –conf-path=/usr/local/etc/nginx/nginx.conf –sbin-path=/usr/local/sbin/nginx --pid-path=/var/run/nginx.pid –error-log-path=/var/log/nginx-error.log --user=www --group=www –with-file-aio –http-client-body-temp-path=/var/tmp/nginx/client\_body\_temp –http-proxy-temp-path=/var/tmp/nginx/proxy\_temp –http-fastcgi-temp-path=/var/tmp/nginx/fastcgi\_temp –http-uwsgi-temp-path=/var/tmp/nginx/uwsgi\_temp –http-log-path=/var/log/nginx-access.log --with-http\_flv\_module –with-http\_geoip\_module --with-http\_gzip\_static\_module –add-module=/usr/ports/www/nginx-devel/work/nginx\_mod\_h264\_streaming-2.2.7 –with-http\_realip\_module --with-http\_stub\_status\_module –add-module=/usr/ports/www/nginx-devel/work/nginx\_upload\_module-2.0.12 –add-module=/usr/ports/www/nginx-devel/work/nginx\_uploadprogress\_module-0.8 –with-pcre Posted at Nginx Forum: > **[Re: gzip causing high cpu load for streaming traffic](https://forum.nginx.org/read.php?2,164484,164494#msg-164494)** > > Ok this is weird I noticed tonight high CPU load on two out of three of our stream servers, which are serving mp4 and flv via the pseudo streaming modules. After investigating the differences between the two high CPU boxes and the one low CPU machine... ---
**Author:** ![steveh](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/5fc32e/32.png) [@steveh](https://www.ruby-forum.com/u/steveh)\ **Post date:** [January 8, 2011, 5:07am UTC](https://www.ruby-forum.com/t/gzip-causing-high-cpu-load-for-streaming-traffic/201476/5 "2011-01-08T05:07:30Z")
Ok found the problem the send of the flv or mp4 is being triggered by an X-Accel-Redirect header who’s content type is text/html. It seems this header is maintained by nginx when processing the flv send instead of setting up one from the configured mime.types. This is because the flv modules calls ngx\_http\_set\_content\_type to set this up which returns NGX\_OK without making any changes if there is already content\_type for the request. An existing content\_type already seems to be being inherited from the original response containing the X-Accel-Redirect header, hence no change and the problem. The docs clear state this is the case here: > **[XSendfile | NGINX](https://www.nginx.com/resources/wiki/start/topics/examples/xsendfile/)** > > Examples that demonstrate how to use the X-Accel-Redirect header with NGINX. This doesn’t effect mp4’s which I was testing with originally as the mp4 module blindly sets video/mp4 so works fine in this case. So sorry for the noise all a case of gotcha I’m afraid. Posted at Nginx Forum: > **[Re: gzip causing high cpu load for streaming traffic](https://forum.nginx.org/read.php?2,164484,164504#msg-164504)** > > Ok this is weird I noticed tonight high CPU load on two out of three of our stream servers, which are serving mp4 and flv via the pseudo streaming modules. After investigating the differences between the two high CPU boxes and the one low CPU machine... ---
**Author:** ![steveh](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/5fc32e/32.png) [@steveh](https://www.ruby-forum.com/u/steveh)\ **Post date:** [January 8, 2011, 4:14am UTC](https://www.ruby-forum.com/t/gzip-causing-high-cpu-load-for-streaming-traffic/201476/6 "2011-01-08T04:14:20Z")
For reference I’m pretty sure that its not connection setup / negotiation that is causing the load when enabled as the machines aren’t dealing with that may new connections per second, so its an overhead for the entirety of the data send I believe. Ok so found something interesting, while mp4’s are being sent with the correct header flv’s aren’t and hence are getting compressed: GET /streaming/test.flv?.. nginx/0.8.53 Date Sat, 08 Jan 2011 03:01:24 GMT Content-Type text/html; charset=utf-8 Content-Length 693656659 Last-Modified Fri, 07 Jan 2011 16:19:25 GMT Connection keep-alive Cache-Control private, max-age=0, must-revalidate Accept-Ranges bytes GET /streaming/test.mp4?.. Server nginx/0.8.49 Date Sat, 08 Jan 2011 03:09:25 GMT Content-Type video/mp4; charset=utf-8 Content-Length 53385372 Last-Modified Wed, 05 Jan 2011 14:55:46 GMT Connection keep-alive Cache-Control private, max-age=0, must-revalidate X-Mod-H264-Streaming version=2.2.7 Accept-Ranges bytes So the question is now why are flv’s getting text/html as their content type? Posted at Nginx Forum: > **[Re: gzip causing high cpu load for streaming traffic](https://forum.nginx.org/read.php?2,164484,164496#msg-164496)** > > Ok this is weird I noticed tonight high CPU load on two out of three of our stream servers, which are serving mp4 and flv via the pseudo streaming modules. After investigating the differences between the two high CPU boxes and the one low CPU machine...