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John Hawkes <hawkes@babylon.engr.sgi.com> wrote: > > David Mosberger suggests raising this issue on LKML to encourage a search > for a more general solution to my ia64 problem. > > My specific problem is that the generic ia64 sched_clock() is broken for > "drifty ITC" (the per-CPU cycle counter clock) platforms, such as the SGI > sn. sched_clock() currently uses its local CPU's ITC and therefore on > drifty platforms its values are not synchronized across the CPUs. This > results (in part) in an invalid load_balance() is-the-cache-hot-or-not > calculation. Requiring that sched_clock() be synchronised is difficult for some platforms. Clearly, it is better if we can relax that. > However, David Mosberger rejected this patch, and he seeks instead some > hypothetical more generic approach to "drifty timebase platforms". One > possible generic change would be to relax the semantics of sched_clock() to > no longer expect that the values be synchronized across all CPUs. Your patch to kernel/sched.c looks good: low overhead, simple, Ingo likes it. Could you please finalise it, cook up the ia64 and numaq implementations and send it over? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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