On 27.11.19 23:32, Hans van Kranenburg wrote:
Hi all,
On 11/27/19 12:13 PM, Durrant, Paul wrote:
-----Original Message-----
From: Ian Jackson <ian.jack...@citrix.com>
Sent: 27 November 2019 11:10
[...]
Subject: RE: [Xen-devel] [PATCH for-4.13 2/2] Rationalize max_grant_frames
and max_maptrack_frames handling
Durrant, Paul writes ("RE: [Xen-devel] [PATCH for-4.13 2/2] Rationalize
max_grant_frames and max_maptrack_frames handling"):
-----Original Message-----
From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf Of
Ian
Jackson
I have seen reports of users who ran out of grant/maptrack frames
because of updates to use multiring protocols etc. The error messages
are not very good and the recommended workaround has been to increase
the default limit on the hypervisor command line.
It is important that we don't break that workaround!
Alas it has apparently been broken for several releases now :-(
I guess at least in Debian (where I have seen this) we haven't
released with any affected versions yet...
I believe the problem was introduce in 4.10, so I think it would be prudent to
also back-port the final fix to stable trees from then on.
Yes, the max grant frame issue has historically always been a painful
experience for end users, and Xen 4.11 which we now have in the current
Debian stable has made it worse compared to previous versions indeed.
Changing the hypervisor command line worked in the past, and now that
value is overwritten again by a lower value in the toolstack, which
requires setting per-domU settings, or, what I did, just additionally
also setting max_grant_frames in /etc/xen/xl.conf to the same value as
the hypervisor command line.
This change is very welcome, even to 4.11-stable if possible, since it
will not break existing configuration of users.
If changing only the value of the hypervisor command line works again,
then old information that shows up when the users searches the web will
be useful again, which is good.
Hans
P.S. Now I'm curious to figure out what a maptrack frame is, didn't hear
about that one before.
The maptrack frames are used by the hypervisor for keeping track which
grants are mapped by a specific domain. So they are necessary for driver
domains (including dom0), and max_maptrack_frames limits how many
mappings of other domain's pages can be active simultaneously in a
domain.
Juergen
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