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From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] [PATCH 6/6] qmp: add balloon-get-memory-stats & event |
Date: | Fri, 17 Feb 2012 10:55:41 -0600 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.23) Gecko/20110922 Lightning/1.0b2 Thunderbird/3.1.15 |
On 02/08/2012 02:30 PM, Luiz Capitulino wrote:
This commit adds a QMP API for the guest provided memory statistics (long disabled by commit 07b0403dfc2b2ac179ae5b48105096cc2d03375a). The approach taken by the original commit (625a5befc2e3200b396594f002218d235e375da5) was to extend the query-balloon command. It introduced a severe bug though: query-balloon would hang if the guest didn't respond. The approach taken by this commit is asynchronous and thus avoids any QMP hangs. First, a client has to issue the balloon-get-memory-stats command. That command gets the process started by only sending a request to the guest, it doesn't block. When the memory stats are made available by the guest, they are returned to the client as an QMP event. Signed-off-by: Luiz Capitulino<address@hidden>
Do we need this to be stable in 1.1?We can do this pretty nicely through QOM. We can have a polling property in the virtio-balloon driver, that when set, will enable the virtio-balloon device to poll the guest for statistics.
We can also have properties for each of the memory statistics and a timestamp for when the last update was.
I think this is a friendlier approach for clients, and a cleaner approach from a QEMU perspective.
There's nothing generic about this functionality. It's extremely specific to virtio-balloon. We just lacked ways to expose device specific function pre-QOM.
Regards, Anthony Liguori
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