linux-kernel - Re: [PATCH V2 0/2] perf/x86/intel/pt: Add support for event tracing and TNT disabling

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Message-ID: <YgvMCYtt14EQgySP@hirez.programming.kicks-ass.net>
Date:   Tue, 15 Feb 2022 16:51:37 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        H Peter Anvin <hpa@...or.com>
Subject: Re: [PATCH V2 0/2] perf/x86/intel/pt: Add support for event tracing
 and TNT disabling

On Tue, Feb 15, 2022 at 05:40:45PM +0200, Adrian Hunter wrote:
> On 15/02/2022 17:35, Peter Zijlstra wrote:
> > On Wed, Jan 26, 2022 at 12:48:13PM +0200, Adrian Hunter wrote:
> >> Hi
> >>
> >> As of Intel SDM (https://www.intel.com/sdm) version 076, there are 2 new
> >> Intel PT features called Event Trace and TNT-Disable.
> >>
> >> Event Trace exposes details about asynchronous events such as interrupts
> >> and VM-Entry/Exit.
> >>
> >> TNT-Disable disables TNT packets to reduce the tracing overhead, but with
> >> the result that exact control flow information is lost.
> > 
> > What's a TNT?
> 
> The TNT packet indicates whether conditional branches were taken
> or not taken.

Thanks, updated that Changelog.