Re: [Xen-devel] Re : task btrfs-transacti:651 blocked for more than 120 seconds

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Sep 28, 2017 at 03:04:02PM +0000, Olivier Bonvalet wrote:
> Le jeudi 28 septembre 2017 à 12:16 +0200, Olivier Bonvalet a écrit :
> > It's a Debian Stretch system, running a 4.9.52 Linux kernel (on a Xen
> > 4.8.2 hypervisor).
> > With an old 4.1.x Linux kernel, I haven't any problem.
> 
> Just a precision, this VM have 26 block devices attached.
> Don't know if that can be related.

Quite likely. With so many PV block devices attached you either have
to limit the number of queues and persistent grants per-device, or
expand the number of grants allowed by Xen.

Can you try to set the following in the Xen command line [0] and see
if that solves your issues:

gnttab_max_frames=64

Roger.

[0] http://xenbits.xenproject.org/docs/unstable/misc/xen-command-line.html

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