Messages in this thread | | | Date | Fri, 27 Feb 2009 15:25:59 +1100 | From | Paul Mackerras <> | Subject | Re: [PATCH] cpuacct: add a branch prediction |
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Ingo Molnar writes:
> * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > > > On Thu, 2009-02-26 at 21:06 +0900, KAMEZAWA Hiroyuki wrote: > > > Hmm.. some routine like > > > atomic64_read() can help this ? (But I don't want to use atomic_t here..) > > > > Yeah, atomic64_t has been proposed numerous times, and x86 > > could actually implement that using cmpxchg8b, just not sure > > about all the other 32bit archs, and if we start using it in > > the scheduler, they'd better have it implemented. > > I have written a working atomic64_t implementation for > tip:perfcounters/core, for 32-bit x86.
atomic64_t would be a big problem for 32-bit powerpc. We'd have to use an array of spinlocks, or make atomic64_t actually be 12 bytes so we have a lock word to use.
Paul.
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