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Date: Mon, 30 Mar 2015 13:41:12 -0600
From: David Ahern <dsahern@gmail.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Stephane Eranian <eranian@google.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, Jiri Olsa <jolsa@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        John Stultz <john.stultz@linaro.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH] perf, record: Add clockid parameter
References: <tip-34f439278cef7b1177f8ce24f9fc81dfc6221d3b@git.kernel.org> <20150327143201.GG21418@twins.programming.kicks-ass.net> <55158F25.9040100@gmail.com> <20150327172059.GK23123@twins.programming.kicks-ass.net> <551594DD.7050705@gmail.com> <20150327201534.GD6291@redhat.com> <20150327215942.GL23123@twins.programming.kicks-ass.net> <CABPqkBR_ou8E01kRmDOBb72ngcdzBkfVPNUj71XWnsYE6i0Bdg@mail.gmail.com> <20150328075549.GG27490@worktop.programming.kicks-ass.net> <551986BC.3000409@gmail.com> <20150330193318.GF23123@twins.programming.kicks-ass.net>
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On 3/30/15 1:33 PM, Peter Zijlstra wrote:
> On Mon, Mar 30, 2015 at 11:24:12AM -0600, David Ahern wrote:
>> This works but the result is not always intuitive as to why it failed.
>>
>> On a kernel that does not support the clock id you get:
>>      $ perf sched record -k mono -- sleep 1
>>      Error:
>>      clockid not supported.
>>
>> And on a kernel that supports clockid but not for NMI:
>>
>>      $ perf record -k realtime -a -- sleep 1
>>      Error:
>>      clockid not supported.
>>
>>      --> H/W counters so realtime is not allowed
>>
>> Same message though different root causes.
>
> Heh, ok I can fudge that :-)
>

What about having the kernel return 'not supported' error for the latter 
-- H/W counters with unsafe clock?