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Re: [Xen-devel] [PATCH] xen: Implement domain runstates

To: Keir Fraser <keir@xxxxxxx>
Subject: Re: [Xen-devel] [PATCH] xen: Implement domain runstates
From: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Date: Tue, 23 Nov 2010 15:48:33 +0000
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On 23/11/10 15:00, Keir Fraser wrote:
Well, actually what we care about is #users-who-care. Plumbing into xentop
to satisfy an acceptance criteria is probably misguided. Reducing
patch-queue length just to make a patch-queue short is also probably
misguided.

I wouldn't offer to put it in xentop just because I wanted to get the patch out of the patchqueue. I think it's a useful feature, that many people would use if they knew about it. If I didn't think it was useful, by far the simplest way to get it out of the patchqueue would be to simply remove the functionality from the next release of XenServer.

I think the "wait for people to ask for it" won't work very well for this particular feature, because it's not the kind of thing I think most people would think to ask for. A bit like tmem -- I think it's a solution to a problem that people have that's very non-obvious, and must therefore be suggested to people rather than waiting for them to ask for it. I could write a blog post about it or otherwise try to promote the idea, but how many people are going to download a patch in order to try it out?

(I'm aware the difference is that tmem's effectiveness can be measured with benchmarks while this feature cannot; I'm just saying that in both cases, you'd be waiting for a long time for people to demand it.)

xenalyze will calculate and report domain runstate numbers based on vcpu runstate_change records, and I've found it useful to get a rough idea what's going on when I get traces in from the field.

Of course there's no rush, but it's likely to be forgotten about for another two years. :-) (It's already been in the XS patchqueue since September 2008.)

 -George

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