Messages in this thread | | | Date | Tue, 2 Jun 2009 12:20:08 -0400 | From | Chris Mason <> | Subject | Re: [benchmark] 1% performance overhead of paravirt_ops on native kernels |
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On Tue, Jun 02, 2009 at 08:22:57AM -0700, Ulrich Drepper wrote: > On Tue, Jun 2, 2009 at 8:03 AM, Chris Mason <chris.mason@oracle.com> wrote: > > The idea that people shipping xen aren't interested in performance > > regressions is really strange to me. > > Why? They have a different base line. For them any regression to > bare hardware performance is even a positive (since it means the gap > between hardware and virt shrinks).
And we would have gotten away with it too if it weren't for you meddling kids!
> > > > Dynamic patching is a big wad of duct tape over the problem. > > And what do you call the Xen model? It's a perfect fit IMO. > > > I'm not saying to take harmful code, I'm saying to take code with a > > small performance regression under a specific CONFIG_. Slub regresses > > more than 1% on database loads, CONFIG_SCHED_GROUPS, the list goes on > > and on. > > None of those have to be enabled in default kernels. > > > > The best place to fix xen is in the kernel. > > No. The best way to fix things is _on the way into the kernel_.
It all depends on which parts are causing problems. A 1% performance hit, under a CONFIG_ that can be disabled? If maintainers are focusing on details like this for long term and active projects, we're doing something very wrong.
-chris
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