> -----Original Message----- > From: Roger Pau Monné <roger....@citrix.com> > Sent: 20 November 2019 11:06 > To: Durrant, Paul <pdurr...@amazon.com> > Cc: xen-devel@lists.xenproject.org > Subject: Re: [Xen-devel] grant table size > > On Wed, Nov 20, 2019 at 09:43:59AM +0000, Durrant, Paul wrote: > > I've dealt with a few problems over the years where the root cause was a > guest running out of grant table and so I'm wondering whether it would be > a good idea to allow a toolstack to increase the table size of a running > guest, e.g. when plugging in a new PV interface. > I would rather have a new xl command that does the grant table > increase (ie: xl set-max-grant-frames) instead of doing it when > plugging new interfaces. >
That would be ok too... Just thought it might be nicer if it were automatic but it would indeed be complete guess-work in libxl to come up with a per-interface grant table quota. > > It would appear that current Linux guests would not be able to make use > of this as it stands (but that could be fixed), but as far as I can tell a > pvops kernel would not misbehave if the maximum table size were to > increase. Similarly Windows PV drivers would need modification to make use > of a dynamic maximum table size but would not misbehave as is. > > Does anyone have any objection to the idea? > > Do you have in mind to signal this somehow to guests, or the > expectation is that the guest will have to poll GNTTABOP_query_size > and at some point the size will increase? > I don't think the guest need care until its grant table grows to the max. At that point, rather than giving up, the guest would re-query the max value to see if there is now more headroom and then re-size its internal data structures accordingly. Paul _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
