Messages in this thread | | | Date | Wed, 8 Jun 2011 12:35:09 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH v5 8/9] x86-64: Emulate legacy vsyscalls |
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* Andi Kleen <andi@firstfloor.org> wrote:
> > eventually may even go away as time progresses and linux systems > > begin to fully rely on the vdso instead. > > That assumes that everyone uses glibc and also updates their > userland. As pointed out many times that's a deeply flawed > assumption.
No, it does not assume it: if a particular usecase cares *so* little about updates that it won't ever update their userland and kernel then they have no problem: they'll have what they had before.
If they are willing to update the *kernel* then they will have to consider what every kernel update brings with itself: legacy facilities are de-emphasised all the time (while the ABI is still fully guaranteed) so user-space should not assume that newer kernels will offer the exact same performance tradeoffs as before.
Nor do i think have you cited any *real* example - you are just talking hypotheticals with very little specifics. ABI does not mean 'executes the same instructions', guaranteeing that would be crazy.
Thanks,
Ingo
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