Il giorno 02/giu/2014, alle ore 15:02, Pavel Machek [off-list ref] ha scritto:

Hi!

quoted

quoted

Well, it's all about how to actually route the changes and in general
whenever avoidable we try to avoid whole-sale code replacement
especially when most of the structural code is similar like in this
case.  Gradually evolving cfq to bfq is likely to take more work but
I'm very positive that it'd definitely be a lot easier to merge the
changes that way and people involved, including the developers and
reviewers, would acquire a lot clearer picture of what's going on in
the process.  For example, AFAICS, most of the heuristics added by

Would it make sense to merge bfq first, _then_ turn cfq into bfq, then
remove bfq?

That way

1. Users like me would see improvements soon 

2. BFQ would get more testing early. 

Like this: I applied patch over today's git... 

I only see last bits of panic...

Call trace:
__bfq_bfqq_expire
bfq_bfqq_expire
bfq_dispatch_requests
sci_request_fn
...
EIP: T.1839+0x26
Kernel panic - not syncing: Fatal exception in interrupt
Shutting down cpus with NMI

...

Will retry.

Any ideas?
			

We have tried to think about ways to trigger this failure, but in vain. Unfortunately, so far no user has reported any failure with this last version of bfq either. Finally, we have gone through a new static analysis, but also in this case uselessly.

So, if you are willing to retry, we have put online a version of the code filled with many BUG_ONs. I hope they can make it easier to track down the bug. The archive is here:
http://algogroup.unimore.it/people/paolo/disk_sched/debugging-patches/3.15.0-rc8-v7rc5.tgz

Should this attempt be useless as well, I will, if you do not mind, try by asking you more details about your system and reproducing your configuration as much as I can.

Thanks,
Paolo

						Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html