linux-kernel - Re: [PATCH] perf, tools: Disable branch flags/cycles for --callgraph lbr

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Date:	Mon, 14 Dec 2015 10:55:38 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	acme@...nel.org, jolsa@...nel.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] perf, tools: Disable branch flags/cycles for --callgraph
 lbr

On Fri, Dec 11, 2015 at 04:12:24PM -0800, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> [The kernel patch needed for this is in tip now
> (b16a5b52eb9 perf/x86: Add option to disable ...)
> So this user tools patch to make use of it should be merged now]
> 
> Automatically disable collecting branch flags and cycles with
> --call-graph lbr. This allows avoiding a bunch of extra MSR
> reads in the PMI on Skylake.
> 
> When the kernel doesn't support the new flags they are automatically
> cleared in the fallback code.
> 
> v2: Switch to use branch_sample_type instead of sample_type.
> Adjust description.
> Fix the fallback logic.
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka
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