On Tue, Dec 19 2006, Jon Escombe wrote: > Jens Axboe wrote: > > On Tue, Dec 19 2006, Arjan van de Ven wrote: > >> On Tue, 2006-12-19 at 10:35 +0200, Dan Aloni wrote: > >>> Hello, > >>> > >>> scsi_execute_async() has replaced scsi_do_req() a few versions ago, > >>> but it also incurred a change of behavior. I noticed that over-queuing > >>> a SCSI device using that function causes I/Os to be starved from > >>> low-level queuing for no justified reason. > >>> > >>> I think it makes much more sense to perserve the original behaviour > >>> of scsi_do_req() and add the request to the tail of the queue. > >> Hi, > >> > >> some things should really be added to the head of the queue, like > >> maintenance requests and error handling requests. Are you sure this is > >> the right change? At least I'd expect 2 apis, one for a head and one for > >> a "normal" queueing... > > > > It does sounds broken - head insertion should only be used for careful > > internal commands, not be the default way user issued commands. Looking > > at the current users, the patch makes sense to me. > > > > It's worth noting that the hdaps disk protection patches rely on the > current behaviour to add 'IDLE IMMEDIATE WITH UNLOAD' commands to the > head of the queue.. Another function, or a new parameter for queue > position would be needed to retain this functionality - any preference > for either? The hdaps disk protection should not be using the SCSI internal function, so it should not be an issue. The block layer API exposes both front/back/sort insertion possibilities. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
