On Tue, 2007-05-29 at 15:40 -0600, Moore, Eric wrote: > On Tuesday, May 22, 2007 3:27 PM, James Bottomley wrote: > > > On Tue, 2007-05-22 at 14:25 -0600, Doug Chapman wrote: > > > Eric, > > > > > > Sorry to bother you on this again, I realize you are very busy. > > > > > > >From our off-list email and from your comments to Chip Coldwell in > > > redhat BZ 225177 it sounded like you were prepared to ACK this. Any > > > chance you could send your official ACK so this can be committed? > > > > > > much appreciated, > > > > Actually I'd like a little analysis of why first, please Eric. > > > > It seems to me, with the current wrong ordering in the initialisation > > results in a large queue depth being given to the DVD (which are > > habitually very low queue depth ... or even untagged beasts). So does > > the slowdown result from the fusion accepting N commands for > > the DVD and > > then rejecting N-1 of them resulting in ping pong between the > > mid-layer > > and driver? > > > > If so, we probably want to fix the command throttling in the driver. > > > > James - Sorry, for delay, somehow I missed this email. > > I approve the patch that was submitted by Doug Chapman. Here is the > reasoning: The DVD device that Doug is using is either a SCSI_1 > device, or it doesn't support Q-tags. The problem is the driver is > setting the Queue depth to 32, when it should of been 1. With the > queue depth set larger than one, this device doesn't work properly.
The device is presumably returning BUSY when you try to send a second command when it's already processing the first ... that should be propagated back to the mid-layer causing it to throttle the queue ... it seems this wasn't happening for some reason to get such a massive slowdown. Is this a more generic problem in the fusion or is it a simple issue only affecting the untagged case? > This bug came about when I reorganized some spi functions by moving them > from mptscsih.c over to mptspi.c. When I did that, there were some > flags not set correctly in mptscsih_change_queue_depth. The function > that sets these flags is mptspi_setTargetNegoParms. Prior to > reorganizing the code, I was calling mptscsi_setTargetNegoParms before I > set the queue depth, the current code does it after. If you accept > this patch, then it sets the flags properly. James - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
