Re: [PATCH resend] bsg: Add support for submitting requests at tail of queue

[Jens Axboe <jens.axboe@oracle.com>]

On Tue, Mar 24 2009, FUJITA Tomonori wrote:
> On Tue, 24 Mar 2009 13:14:38 +0100
> Jens Axboe <jens.axboe@oracle.com> wrote:
> 
> > On Tue, Mar 24 2009, FUJITA Tomonori wrote:
> > > On Tue, 24 Mar 2009 10:41:32 +0200
> > > Boaz Harrosh <bharrosh@panasas.com> wrote:
> > > 
> > > > Boaz Harrosh wrote:
> > > > > Hi Tomo Jens
> > > > > 
> > > > > Tomo you never ack-by on this patch. I absolutely needs this for the
> > > > > user-mode API of osd-initiator. Which is needed with up-coming exofs
> > > > > utilities.
> > > > > 
> > > > > What do you want to do?
> > > > > 
> > > > > Thanks 
> > > > > 
> > > > 
> > > > Hi Jens.
> > > > 
> > > > I absolutely need this patch for 2.6.30 merge window. It is totally
> > > > un-dangerous since defaults are left unchanged.
> > > 
> > > The question is we really need this feature or not. Though I guess
> > > that we need to address this starvation issue.
> > 
> > I'd argue that tail insertion should be the most used way to queue
> > commands, head insertion should only be for the cases where you want
> > immediate access (like error handling).
> 
> As I wrote, I think that we need to address this starvation issue.
> 
> But nobody has complained about this (with sg and bsg) for years
> because we have not seen applications sending scsi commands that are
> many enough to make a queue full. So it's worth knowing what unknown
> applications do for what, I think.

Not sure it exists, just saying that if I were to write an app that uses
bsg for doing "normal" IO, I would certainly use tail insertion.

-- 
Jens Axboe