> -----Original Message-----
> From: James Bottomley [mailto:[email protected]]
> Sent: Wednesday, January 24, 2007 9:00 AM
> To: Ed Lin
> Cc: linux-scsi; linux-kernel; jeff; Promise_Linux
> Subject: Re: [patch] scsi: use lock per host instead of per
> device forshared queue tag host
>
...
>
> This patch looks OK in principle.
>
> However, are you sure you're not using a sledgehammer to crack a nut?
> If the only reason you're doing this is because of the shared tag map,
> then probably that should be the area you protect with a per-tag-map
> lock. The net effect of what you've done will be to serialise all
> accesses to your storage devices. For a small number of devices, this
> probably won't matter than much, but for large numbers of devices,
> you're probably going to introduce artificial performance
> degredation in
> the I/O scheduler.
>
> James
>
Thanks.
Maybe this issue needs more discussion. I'll follow up.
Ed Lin