Does with-aio-support work?

[Volker Lendecke]

On Thu, Aug 19, 2010 at 09:43:37AM -0400, Yuehai Xu wrote:
> Since the processes in the client are very simple program that I
> write, they just read data with certain stride size, so, the
> asynchronous from client should work. Is it because I use cifs to
> mount the directory from samba server so that no asynchronous requests
> are found? You have said I need to look at the specific docs when
> cifsfs is used, but the client is also running in Linux, is it
> different that I use smbclient to read data or mount with cifsfs and
> then read?

Yes, using a cifs mountpoint is different from using
smbclient. I would have to look into the network traces to
see whether cifs can multiplex different processes in a way
that requests are sent out in parallel. I would hope it does
so, but I'm pretty certain that for example smbfs does not
do that, neither does smbclient before version 3.2.

> In my opinion, because smbd might handle several clients at the same
> time, so, dispatching the requests from different clients
> asynchronously does make sense because it is no need for one client to
> wait for the completion of request from another client.

This right now is being taken care of by the fact that Samba
uses a process per client.

> Should this be the motivation to use libaio?

We're not using libaio, we're using the glibc async io
facilities. Async I/O is just not supported propely in the
Linux kernel, this has to be done in user space with
multiple threads or processes.

Volker