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

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.

Dongli Zhang

>> With Xen 4.8, you can add gnttab_max_frames=64 (or another number, but
>> higher than the default 32) to the xen hypervisor command line and reboot.
> admin@: I made the modification in the grub config. We can probably try
> to reboot with the newer hypervisor, and monitor that value.
> Samuel
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