Does with-aio-support work?

[Volker Lendecke]

On Wed, Aug 18, 2010 at 06:03:13PM -0400, Yuehai Xu wrote:
> The version of my samba is 3.3.2 and I rebuild it with the configure
> "--with-aio-suport". Then, I just follow the man of smb.conf, adding "
> aio read size = 1" to my smb.conf. The, the read request dispatched by
> smbd should be asynchronous, is that correct?
> 
> I am puzzled about it. I use another Linux machine mount a certain
> directory of my samba server with cifs, then, I start 4 processes to
> read files in this directory concurrently. In order to avoid
> readahead, I set the stride size between each read request of a
> process to 8K, in that way, readahead should not work. According to
> the man, the requests from different process should be asynchronous to
> each other.
> 
> I know that if I run processes in different machine, multi smbds will
> handle these requests and they are of course asynchronous, however,
> will a smbd handle all requests from a client? If there are several
> processes in this client, are the requests async? I trace the requests
> using blktrace, and find that even I have set "aio read size = 1", all
> the requests are sync because I use only one client machine on which
> there are multi processes.
> 
> So, I am wondering, what does asynchronous here really mean?

You need to look at the network trace. Samba aio will help
in the case where the client issues multiple requests at
once. If your client does not do that, aio will not do any
good. You will see this behaviour with smbclient >= 3.2. For
other clients like Windows, cifsfs or smbfs you need to look
at the specific docs of those clients. --with-aio-support is
a pure server setting.

Volker