Re: [Xen-devel] [PATCH 4 of 5 V3] tools/libxl: Control network buffering in remus callbacks [and 1 more messages]

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Shriram Rajagopalan writes ("Re: [PATCH 4 of 5 V3] tools/libxl: Control network 
buffering in remus callbacks [and 1 more messages]"):
> Frankly I don't know. At the moment, I am trying to make sure that
> the libxl-remus implementation is correct before I attempt to make
> it fast.
> 
> With/without these patches, there is a huge overhead per
> checkpoint. I cannot get to a 20ms checkpoint interval. Time to
> suspend/resume a domain is on the order of tens of milliseconds even
> if it was a PV domain with fast suspend support -- where it used to
> take under 1ms to suspend, checkpoint and resume an idle PV domain
> on Xend+Remus.

Oh dear.

> This was one of the issues I raised a long time back. And this is
> currently the second element in my queue, the first being to get the
> patches mainline, then slowly tighten up relevant code for
> performance.

I think this is probably a bad approach.  Under the circumstances, it
seems like you really need to move the relevant code lower in the call
stack.  In particular, you want everything to be handled synchronously
in the same process as is doing the save/restore, at least for PV
domains.

That's likely to involve substantially rewriting it.

Ian.

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