sd-readahead — Reference implementation of APIs for controlling boot-time read-ahead
#include "sd-readahead.h"
sd-readahead.c and
                sd-readahead.h provide a
                reference implementation for APIs for controlling boot-time
                read-ahead, as implemented by the read-ahead subsystem
                of the
                systemd(1)
                init system.
See sd_readahead(3) for more information about the function implemented.
This interface is provided by the reference implementation of APIs for controlling boot-time read-ahead and distributed with the systemd package. The algorithms it implements are simple, and can easily be reimplemented in daemons if it is important to support this interface without using the reference implementation. See the respective function man pages for details.
In addition, for details about the algorithms check the liberally licensed reference implementation sources: http://cgit.freedesktop.org/systemd/systemd/plain/src/readahead/sd-readahead.c and http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-readahead.h
These APIs are implemented in the reference
                implementation's drop-in
                sd-readahead.c and
                sd-readahead.h files. It is
                recommended that applications consuming these APIs copy
                the implementation into their source tree, either
                verbatim or in excerpts. These interfaces are
                currently not available in a dynamic library.
The functions provided by this interface become
                NOPs when -DDISABLE_SYSTEMD is set during
                compilation. In addition, if
                sd-readhead.c is compiled on
                non-Linux systems it becomes NOPs.