Messages in this thread | | | Date | Wed, 04 Apr 2007 08:43:39 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [patch 04/17] Add pagetable accessors to pack and unpack pagetable entries |
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Ingo Molnar wrote: > the main metric we are interested in is the overhead for people who just > want to run the non-patched native kernel that has CONFIG_PARAVIRT > enabled (99%+ of the users at the moment), so the delta is: > > null: +12.0% > null IO: +7.5% > stat: within noise > open/close: within noise > TCP: ~5.0% > signal install: 2.0% > signal handle: 4.7% > fork: 2.7% > exec: 3.6% > shell: 3.6% > Hm, I don't think you can get this much precision out of these numbers. I noticed larger variations from boot-to-boot running the same test.
> this is not 'barely measurable' but 'BLOODY LARGE' overhead.
Yes. Fortunately there's a noticable difference between native and unpatched paravirt, because it shows all the effort we put into patching is worthwhile.
>> paravirt, patching >> ezr Linux 2.6.21- 1000 0.25 0.53 31.8 34.4 10.1 1.04 5.44 730. 1583 4600 >> ezr Linux 2.6.21- 1000 0.26 0.55 32.1 35.2 13.3 1.03 5.48 748. 1589 4606 >> ezr Linux 2.6.21- 1000 0.26 0.54 32.0 34.9 14.1 1.04 5.43 752. 1606 4647 >> > > i guess this pretty much makes the case for patching ... >
Right, that's why there's patching.
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