On Mon, May 04, 2015 at 02:42:20PM +0200, Hannes Reinecke wrote: > The current ALUA device_handler has two drawbacks: > - We're sending a 'SET TARGET PORT GROUP' command to every LUN, > disregarding the fact that several LUNs might be in a port group > and will be automatically switched whenever _any_ LUN within > that port group receives the command. > - Whenever a LUN is in 'transitioning' mode we cannot block I/O > to that LUN, instead the controller has to abort the command. > This leads to increased traffic across the wire and heavy load > on the controller during switchover. > > With this patch the RTPG handling is moved to a workqueue, which > is being run once per port group. This reduces the number of > 'REPORT TARGET PORT GROUP' and 'SET TARGET PORT GROUPS' which > will be send to the controller. It also allows us to block > I/O to any LUN / port group found to be in 'transitioning' ALUA > mode, as the workqueue item will be requeued until the controller > moves out of transitioning. I'm having a hard time understanding the workqueue use here. What is the benefit of that one worker function to do everything? It seems having a work struct in struct alua_queue_data to just run STPG, and a different one to run RPTG in the port group structure would be more sensible instead of interwinding them. Also why do you need the sigle threaded workqueue? That seems like a possible limiting factor in a large enough system having to deal with a cable disconnect cutting off multiple port groups, or just during bootup. -- 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
