Gzip vs. sendfile

[Joó Ádám]

Hi,

>From <https://www.nginx.com/blog/tuning-nginx/>:

> Note, however, that because the data never touches user space it’s not subject to the filters in the regular NGINX processing chain. As a result, filters that change content, for example the gzip filter, have no effect.

Which never occurred to me, but sounds reasonable. What is more
surprising is that I found virtually no discussion on this, and I
wasn’t able to reproduce it.

Using the following configuration:

    types {
        text/plain txt;
    }

    gzip on;
    gzip_comp_level 5;
    gzip_types text/plain;

    sendfile on;

the files are still served gzipped. The author of
http://expertdevelopers.blogspot.hu/2013/09/gzip-compression.html
says:

> There is a tradeoff between using compression (saving your bandwidth) and using the sendfile feature (saving your CPU cycles). If the connector supports the sendfile feature, e.g. the NIO connector, using sendfile will take precedence over compression. The symptoms will be that static files greater that 48 Kb will be sent uncompressed.

However, increasing the file size to more than 200 KB still has no
effect on the encoding.

Is it actually the other way around and filters disable sendfile?


Ádám