mod_gzip makes things slower

[ummahforums]

A note to anyone who's thinking of installing mod_gzip:

I installed mod_gzip on my server, disabled the GZIP output in vBulletin and got mod_gzip to handle the compression of PHP output. It slowed down vBulletin's performance.

Now I've re-enabled GZIP output in vBulletin, and got mod_gzip to exclude PHP files, and performance is back to normal again.

[JeffJ]

your performance is back but it will never be as good as running without compression entirely. Just like all other software based compressions scheme; it eats up cpu cycles to compress the data. I've been using VB for almost a year now and I have a very active board. In all of my testing (and I have done quite a bit) I have found that enabling gzip and setting the compression level to 2 works the best.

In addition I get much better page display times by increasing the output buffer size in both apache and php. In apache I use the following setting:
sendbuffersize 64000


and in php, I use these settings:

output_buffering = 40000

and
output_buffering = On
(the default is only 4096)

[ummahforums]

I would have GZIP output off completely, but I do need to save bandwidth. Plus, the users on slow dial-up connections like it!

Many thanks for the Apache & PHP tips!

[George L]

Originally posted by ummahforums
I would have GZIP output off completely, but I do need to save bandwidth. Plus, the users on slow dial-up connections like it!

Many thanks for the Apache & PHP tips!

mod_gzip's compression level is fixed at a higher value = 6

whereas vB's admin gzip can be set to 1 which is less server intensive

i have mod_gzip on my server and it handles fine for my hardware

[fastforward]

Originally posted by eva2000
mod_gzip's compression level is fixed at a higher value = 6

I always wondered what is was set at. Is there no hidden parameter that allows you change it?

[George L]

Originally posted by fastforward
I always wondered what is was set at. Is there no hidden parameter that allows you change it?

not right now from http://i4net.tv/marticle/mod_gzip/enhancements.htm

Possible enhancements in future versions of mod_gzip
This document describes some possible functional enhancements which hopefully could be implemented into the current version 1.3.26.1a of mod_gzip without too much effort and enhance the usability of this module


===

Configurable gzip compression level
Currently mod_gzip uses the gzip compression level 6. This is hard-coded by the assignment gz1->level = 6 inside the function gz1_init.

The higher the compression level, (gzip normally allows values between 0 and 9), the better the compression effect, but the higher the CPU time consumption as well. By adapting this compression level a user could solve the trade-off between CPU load and bandwidth saving according to his own requirements. Own experiments have shown that level 3 already takes you near the effect of compression level 6 - at least the choice between these two values should be left to the user.

Thus it would be reasonable to have this compression level configurable by offering another directive mod_gzip_compression_level

[fastforward]

Originally posted by eva2000
not right now from http://i4net.tv/marticle/mod_gzip/enhancements.htm

So I guess we could just change that in the code and recompile... I might give it a try.

[ccd1]

Is it true that zlib (on php) is a form of mod_gzip hardcoded to 3?

[ummahforums]

Thanks Eva. I guess I need to upgrade my hardware (again!).

Baragon0 - zlib in PHP is not hard-coded to 3. You can set the compression level to whatever you want.

[ummahforums]

Originally posted by fastforward
So I guess we could just change that in the code and recompile... I might give it a try.

I tried that, it compiled fine (I set gz1->level to 3), but after installing it mod_gzip wasn't compressing anything at all!
I went back and set it to 6 again, compiled and installed again, and it worked fine!

[ummahforums]

My vBulletin install is in a directory of the web root called "forum". How do I configure mod_gzip to ignore all files in this directory?

(I want mod_gzip to ignore vBulletin's PHP files, as vBulletin handles the compression itself, but I want it to compress other PHP scripts.)