linux-kernel - Re: [PATCH V2 02/11] perf/x86: Add support for TSC as a perf event clock

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Message-ID: <57bdc43e-4753-66f8-b54b-860be3239026@intel.com>
Date:   Fri, 4 Mar 2022 14:41:16 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        kvm@...r.kernel.org, H Peter Anvin <hpa@...or.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Leo Yan <leo.yan@...aro.org>
Subject: Re: [PATCH V2 02/11] perf/x86: Add support for TSC as a perf event
 clock

On 04/03/2022 14:33, Peter Zijlstra wrote:
> On Mon, Feb 14, 2022 at 01:09:05PM +0200, Adrian Hunter wrote:
>> +u64 perf_hw_clock(void)
>> +{
>> +	return rdtsc_ordered();
>> +}
> 
> Why the _ordered ?

To be on the safe-side - in case it matters.  trace_clock_x86_tsc() also uses the ordered variant.