[Pkg-xen-devel] [admin] [Xen-devel] [BUG] task jbd2/xvda4-8:174 blocked for more than 120 seconds.

[Samuel Thibault]

Hello,

Dongli Zhang, le mar. 12 févr. 2019 12:11:20 +0800, a ecrit:
> On 02/12/2019 06:10 AM, Samuel Thibault wrote:
> > Hans van Kranenburg, le lun. 11 févr. 2019 22:59:11 +0100, a ecrit:
> >> On 2/11/19 2:37 AM, Dongli Zhang wrote:
> >>>
> >>> On 2/10/19 12:35 AM, Samuel Thibault wrote:
> >>>>
> >>>> Hans van Kranenburg, le sam. 09 févr. 2019 17:01:55 +0100, a ecrit:
> >>>>>> I have forwarded the original mail: all VM I/O get stuck, and thus the
> >>>>>> VM becomes unusable.
> >>>>>
> >>>>> These are in many cases the symptoms of running out of "grant frames".
> >>>>
> >>>> Oh!  That could be it indeed.  I'm wondering what could be monopolizing
> >>>> them, though, and why +deb9u11 is affected while +deb9u10 is not.  I'm
> >>>> afraid increasing the gnttab max size to 32 might just defer filling it
> >>>> up.
> >>>>
> >>>>>   -# ./xen-diag  gnttab_query_size 5
> >>>>>   domid=5: nr_frames=11, max_nr_frames=32
> >>>>
> >>>> The current value is 31 over max 32 indeed.
> >>>
> >>> Assuming this is grant v1, there are still 4096/8=512 grant references available
> >>> (32-31=1 frame available). I do not think the I/O hang can be affected by the
> >>> lack of grant entry.
> >>
> >> I suspect that 31 measurement was taken when the domU was not hanging yet.
> > 
> > Indeed, I didn't have the hanging VM offhand.  I have looked again, it's
> > now at 33. We'll have to monitor to check that it doesn't continue just
> > increasing.
> 
> If the max used to be 32 and the current is already 33, this indicates the grant
> entries might be used up in the past before the max_nr_frames is tuned.

The number seems to be going up by about one every day. So probably a
grant entry leak somewhere :/

Samuel