This PR brings two optimizations mainly
for page-cache build-up and how to avoid
getting OOM killed in the process. Although
these memories are reclaimable Linux is not
fast enough to reclaim them as needed on a
very busy system. fadvise is a system call
implemented in Linux to advise page-cache to
avoid overload as we get significant amount
of requests on the server.
- FADV_SEQUENTIAL tells that all I/O from now
is going to be sequential, allowing for more
resposive throughput.
- FADV_NOREUSE tells kernel to start removing
things for this 'fd' from page-cache.
38027c8f52