[Stgt-devel] More threads for device server

[Mike Christie]

FUJITA Tomonori wrote:
> From: Mike Christie <michaelc at cs.wisc.edu>
> Subject: Re: [Stgt-devel] More threads for device server
> Date: Sun, 04 Sep 2005 21:05:12 -0500
> 
> 
>>>The current code uses work queue for performing SCSI commands (or
>>>block target's tasks). Work queue is simple and good enough for
>>>debugging, however, a single thread per CPU is not good enough (from
>>>the performance perspective).
>>>
>>>I thought about creating multiple kernel threads by hand. Are there
>>>handy APIs?
>>
>>you can create a single threaded workqueue per target or session?
> 
> 
> The vfs APIs work synchronously. So we need multiple threads per
> target (or session) to perform several SCSI commands simultaneously.
> 
> If we always use asynchronous block I/O APIs (like AIO vfs,
> submit_bio, etc), a single threaded workqueue would be fine.

I think async is going to be better in the long run since a thread per 
device sounds like a lot. I am not familar with the AIO vfs code so I am 
not much help and my opinion is really more of guess then. I am just 
thinking if we can send more than one command down to the real device at 
once then we could take advatage of the block layers io scheduling or 
something.