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

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>]

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.

Samuel

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