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

[Samuel Thibault <admin@xxxxxxxxxxxxxxxxxxx>]

Hello,

Dongli Zhang, le lun. 11 févr. 2019 09:37:43 +0800, a ecrit:
> On 2/10/19 12:35 AM, Samuel Thibault wrote:
> > Hello,
> > 
> > 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.
> 
> If to increase the max frame to 64 takes effect, it is weird why the I/O would
> hang when there are still 512 entries available.

After reboot with gnttab_max_frames=256, I could let the VM run for some
time, nr_frames is now 32.

Samuel

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