Messages in this thread | | | From | Mike Frysinger <> | Date | Fri, 12 Jun 2009 11:16:52 -0400 | Subject | Re: [PATCH] scripts/checksyscalls.sh: only whine perf_counter_open when supported |
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On Fri, Jun 12, 2009 at 08:05, Ingo Molnar wrote: > * Mike Frysinger <vapier@gentoo.org> wrote: >> If the port does not support HAVE_PERF_COUNTERS, then they can't >> support the perf_counter_open syscall either. Rather than forcing >> everyone to add an ignore (or suffer the warning until they get >> around to implementing support), only whine about the syscall when >> applicable. > > No, this patch is wrong - it's really easy to add support: just hook > up the syscall. This should happen for every architecture really, so > the warning is correct and it should not be patched out. > > PMU support is not required to get perfcounters support: if an > architecture hooks up the syscall it will get generic software > counters and the tools will work as well. > > Profiling falls back to a hrtimer-based sampling method - this is a > much better fallback than oprofile's fall-back to the timer tick. > This hrtimer based sampling is dynticks/nohz-correct and can go > beyond HZ if the architecture supports hrtimers.
these statements are actually incorrect. the perf counter code explicitly requires: - asm/perf_counter.h - support for atomic64 types (unless i missed something, x86 is the only 32bit system that supports these) - some perf stubs (like set_perf_counter_pending() -- prototype really should be in common perf_counters headers rather than forcing the arch to copy & paste the exact same line)
not that any of this is documented ... -mike -- 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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