Messages in this thread |  | | From | Andi Kleen <> | Subject | Re: [-mm patch] x86_64 GTOD: offer scalable vgettimeofday II | Date | Thu, 1 Feb 2007 13:17:45 +0100 |
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On Thursday 01 February 2007 12:46, Ingo Molnar wrote: > > * jbohac@suse.cz <jbohac@suse.cz> wrote: > > > Inter-CPU monotonicity can not, however, be guaranteed in a vsyscall, > > so vsyscall is not used by default. [...] > > note that this is not actually the case. My patch below, ontop of -mm, > implements a fully monotonic gettimeofday as an optional vsyscall > feature. > > The 'price' paid for it is lower resolution - but it's still good for > those benchmarking TPC-C runs - and /alot/ simpler.
BTW another comment: I was told that at least one of the big databases wants ms resolution here. So to make your scheme work would require a HZ=1024 regular interrupt. But that would also make everything slower again due to CPU overhead as it was learned in the 2.4->2.6 HZ transition.
So it might not actually be worth it.
-Andi
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