Re: calling scsi_adjust_queue_depth() during I/O...

[Jens Axboe <axboe@suse.de>]

On Fri, Aug 05 2005, Andrew Vasquez wrote:
> On Fri, 05 Aug 2005, Tejun Heo wrote:
> 
> > >  Oops, forget about the previous mail.  Above patch make it into the 
> > > tree and it's the source of the problem.  My git HEAD was pointing at 
> > > the latest update but I haven't updated my cache, so I was looking at 
> > > the old source tree.  My apologies for the hassle and the bug.
> > > 
> > >  Original code was broken in the following two points.
> > > 
> > >  * tag_index wasn't allocated fully
> > >  * tag_map's extra bits were always initialized w/ 1's.
> > > 
> > >  The first bug is critical and the second bug prevents proper enlarging 
> > > of tag map.  However, the second bug effectively masks the first bug 
> > > avoiding critical problem.  My above mentioned patch broke things 
> > > seriously when reducing tag size on flight.
> > > 
> > >  Again, my apologies and patch will soon follow.
> > 
> >  Here's the fix.  It basically revives bqt->real_max_depth sans
> > allocation optimization in init_tag_map.  I've also added a comment
> > explicitly noting that tag map cannot be shrunk to prevent other
> > morons like me.  :-( Please try this one and let me know how it works.
> > If this is the correct fix, I'll repost properly to Jens and lkml with
> > detailed explanation on how it was broken in the original code and how
> > I broke it with my previous patch.  Sorry.
> 
> OK, 20 minutes into lowering and raising the queue-depth and
> everything appears to be working fine.  I'll continue banging away
> with my configuration and let you know if anything else comes up.
> Looks good so far.

Thanks for fixing it so quickly, Tejun! I'll be on vacation next week,
can you make sure it gets to Andrew?

-- 
Jens Axboe