On Tue, Feb 1, 2011 at 2:26 PM, Jes Sorensen <jes.soren...@redhat.com> wrote: > On 02/01/11 15:12, Stefan Hajnoczi wrote: >> On Tue, Feb 1, 2011 at 10:58 AM, <jes.soren...@redhat.com> wrote: >>> From: Jes Sorensen <jes.soren...@redhat.com> >>> >>> Implement freeze/thaw support in the guest, allowing the host to >>> request the guest freezes all it's file systems before a live snapshot >>> is performed. >>> - fsfreeze(): Walk the list of mounted local real file systems, >>> and freeze them. >>> - fsthaw(): Walk the list of previously frozen file systems and >>> thaw them. >>> - fsstatus(): Return the current status of freeze/thaw. The host must >>> poll this function, in case fsfreeze() returned with a >>> timeout, to wait for the operation to finish. >> >> It is desirable to minimize the freeze time, which may interrupt or >> degrade the service that applications inside the VM can provide. >> Polling means we have to choose a fixed value (500 ms?) at which to >> check for freeze completion. In this example we could have up to 500 >> ms extra time spent in freeze because it completed right after we >> polled. Any thoughts on this? > > I have to admit you lost me here, where do you get that 500ms time from? > Is that the XMLRPC polling time or? I just used the example code from > other agent calls.
500 ms is made up. I was thinking, "what would a reasonable polling interval be?" and picked a sub-second number. Can you explain how the timeout in fsfreeze can happen? It's probably because I don't know the virtagent details. Stefan
