Re: [Nbd] deadlock in nbd?

[Eric Gerlach <egerlach@...135...>]

Peter Daum wrote:
> Hi,
>  
> Mike Snitzer <snitzer@...17...>  wrote:
>  > Which IO scheduler are you using?  Please have a look at this redhat 
> > bug; turns out that there is definitely an issue with cfq (not 
> > exclussive to redhat): 
> > https://bugzilla.redhat.com/show_bug.cgi?id=241540 
>  >
> > But if you're seeing this on stock kernel.org I'd imagine your just 
> > using anticipatory.
>
> ... I'll do some more thorough testing to be sure that this was indeed all of it,
> but at first sight it looks like this is also what is striking me - On all machines
> but one (accidentally also the only one without interface bonding) I had "cfq"
> as the default IO scheduler. After settting the scheduler for /deb/nbd0 to "noop",
> so far it is running without a problem ...

Ha ha!  It works!  Thanks a lot for the pointer.  For future reference 
to other people who may not want to go on a search, the secret password is:

echo noop > /sys/block/nbdX/queue/scheduler (replace X as necessary).

I have only one further question:  Is it safe to change the scheduler 
while the device is mounted?  I'd like to put that command in my 
rc.local, but it will only run after the device is mounted.

Cheers,

Eric