Ubuntu – Identifying what is causing High IO (Linux, Ubuntu)

How do you arrive at your 0.04s rendering time? You might want to want to remove PHP from the equation entirely an benchmark against static files only.

There are a few things you can do to improve your configuration, though. First of all, your gzip compression level can be increased quite safely, the CPU impact is minimal but you can gain a smaller data size by increasing it to 5. I found increasing it further than that rarely yields any benefit.

You can also quite easily increase your keep-alive timeout, the default value is 75. This probably won't help raw throughput much but if a client's browser allows it then it will seem snappier.

After that you might want to use an open-file cache. I use the following configuration:

open_file_cache max=5000 inactive=20s;
open_file_cache_valid    30s;
open_file_cache_min_uses 2;
open_file_cache_errors   on;

You can find the documentation on that here: http://wiki.nginx.org/NginxHttpCoreModule#open_file_cache

Since you have no buffers specified it might be that the buffers aren't large enough and thus the response is stored on temporarily on the disk. You can see if iostat 1 shows a large iowait time.

The interesting buffers are

• client_body_buffer_size
• output_buffer

The client body buffer is documented here: http://wiki.nginx.org/NginxHttpCoreModule#client_body_buffer_size

The output buffer is not documented in the wiki but it takes two arguments, the first one is the amount of buffers and the second one is the size of each of them. The output buffer is primarily used when sendfile is off or if you gzip data before sending it to the user, so you'll definitely want to make sure the data fits.

.bash_profile and .bashrc are specific to bash, whereas .profile is read by many shells in the absence of their own shell-specific config files. (.profile was used by the original Bourne shell.) .bash_profile or .profile is read by login shells, along with .bashrc; subshells read only .bashrc. (Between job control and modern windowing systems, .bashrc by itself doesn't get used much. If you use screen or tmux, screens/windows usually run subshells instead of login shells.)

The idea behind this was that one-time setup was done by .profile (or shell-specific version thereof), and per-shell stuff by .bashrc. For example, you generally only want to load environment variables once per session instead of getting them whacked any time you launch a subshell within a session, whereas you always want your aliases (which aren't propagated automatically like environment variables are).

Other notable shell config files:

/etc/bash_profile (fallback /etc/profile) is read before the user's .profile for system-wide configuration, and likewise /etc/bashrc in subshells (no fallback for this one). Many systems including Ubuntu also use an /etc/profile.d directory containing shell scriptlets, which are . (source)-ed from /etc/profile; the fragments here are per-shell, with *.sh applying to all Bourne/POSIX compatible shells and other extensions applying to that particular shell.