sendfile

Enables or disables the use of sendfile().

Starting from nginx 0.8.12 and FreeBSD 5.2.1, aio can be used to pre-load data for sendfile():

location /video/ {
    sendfile       on;
    tcp_nopush     on;
    aio            on;
}

In this configuration, sendfile() is called with the SF_NODISKIO flag which causes it not to block on disk I/O, but, instead, report back that the data are not in memory. nginx then initiates an asynchronous data load by reading one byte. On the first read, the FreeBSD kernel loads the first 128K bytes of a file into memory, although next reads will only load data in 16K chunks. This can be changed using the read_ahead directive.

Before version 1.7.11, pre-loading could be enabled with aio sendfile;.