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Subject: Re: [PATCH 2/6] perf tools: Store clock references for -k/--clockid
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To:     Jiri Olsa <jolsa@redhat.com>,
        Alexey Budankov <alexey.budankov@linux.intel.com>
Cc:     Jiri Olsa <jolsa@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Michael Petlan <mpetlan@redhat.com>,
        Ian Rogers <irogers@google.com>,
        Andi Kleen <ak@linux.intel.com>,
        =?UTF-8?Q?Genevi=c3=a8ve_Bastien?= <gbastien@versatic.net>,
        Wang Nan <wangnan0@huawei.com>,
        Jeremie Galarneau <jgalar@efficios.com>
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 <20200731161519.GB4296@krava>
From:   David Ahern <dsahern@gmail.com>
Message-ID: <f24e38b0-3000-1306-7058-cc440557e733@gmail.com>
Date:   Fri, 31 Jul 2020 10:35:54 -0600
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On 7/31/20 10:15 AM, Jiri Olsa wrote:
>> It might also want to be implemented in a loop and iteration with minimal
>> time delta is chosen to improve synchronization accuracy and also mitigate
>> possible context switches between gettimeofday() and clock_gettime() calls.
> right, we could make this more accurate.. I'll post some follow up
> change with that

If it is handled through vdso (e.g., x86) both calls should be very fast
with no context switches and the margin of error is well less than the
usec resolution in the output.