Messages in this thread | | | Date | Mon, 17 Oct 2011 11:03:10 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: Linux 3.1-rc9 |
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On Mon, 17 Oct 2011, Ingo Molnar wrote: > * Linus Torvalds <torvalds@linux-foundation.org> wrote: > For the record, i absolutely hate much of the other time related type > obfuscation we do as well. > > For example the ktime_t obfuscation - we only do it to avoid a divide > on 32-bit architectures that cannot do fast 64/32 divisions ... > > It makes the time code a *lot* less obvious than it could be. > > I think we should use one flat u64 nanoseconds time type in the > kernel (preparing it with using KTIME_SCALAR on all architectures for > a release or so), used with very simple and obvious C arithmetics.
It'd be nice, but this simply will not fly.
> That simple time type could then trickle down as well: we could use > it everywhere in kernel code and limit the hodge-podge of ABI time > units to the syscall boundary. (and convert the internal time unit to > whatever ABI unit there is close to the syscall boundary) > > There's a point where micro-optimized 32-bit support related > maintenance overhead (and the resulting loss of > robustness/flexibility) becomes too expensive IMO.
That's not a micro optimization, it's a massive performance hit if you force those 32bit archs to do 64/32 all over the place.
Thanks,
tglx
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