Re: [PATCH] scripts/checksyscalls.sh: only whine perf_counter_open when supported

[Mike Frysinger]

On Fri, Jun 12, 2009 at 08:05, Ingo Molnar wrote:
> * Mike Frysinger <vapier@xxxxxxxxxx> wrote:
>> If the port does not support HAVE_PERF_COUNTERS, then they can't
>> support the perf_counter_open syscall either. ÂRather 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.

if there is generic support available, why must every arch select
HAVE_PERF_COUNTERS in their Kconfig ?
-mike
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/