# Gzip vs. sendfile

**URL:** <https://www.ruby-forum.com/t/gzip-vs-sendfile/243133>\
**Category:** NGINX\
**Created:** [August 24, 2015, 11:50pm UTC](https://www.ruby-forum.com/t/gzip-vs-sendfile/243133 "2015-08-24T23:50:51Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Rafa\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/958977/32.png) [@Rafa\_F](https://www.ruby-forum.com/u/Rafa_F)\
**Post date:** [August 24, 2015, 11:50pm UTC](https://www.ruby-forum.com/t/gzip-vs-sendfile/243133/1 "2015-08-24T23:50:51Z")

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Hi,

From [https://www.nginx.com/blog/tuning-nginx/](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

> **[gzip compression](http://expertdevelopers.blogspot.com/2013/09/gzip-compression.html)**
>
> This time I’ll discuss about usage of gzip compression to make faster web requests. In short “gzip” is a software application for date comp...

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

---

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**Author:** ![JoSSSSdSSm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/5f9b8f/32.png) [@JoSSSSdSSm](https://www.ruby-forum.com/u/JoSSSSdSSm)\
**Post date:** [August 25, 2015, 2:40pm UTC](https://www.ruby-forum.com/t/gzip-vs-sendfile/243133/2 "2015-08-25T14:40:01Z")

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Hello!

On Mon, Aug 24, 2015 at 11:50:10PM +0200, Joó Ádám wrote:

> From [https://www.nginx.com/blog/tuning-nginx/](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.

The statement quoted is incorrect. Instead, if any filter is going  
to change content, sendfile won’t be used. I’ll ping Rick to fix  
this.

[…]

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

Yes.

–  
Maxim D.

> **[nginx](http://nginx.org/)**