linux-kernel - Re: [PATCH v1 07/11] x86: perf: intel

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Message-ID: <874n3wk2xb.fsf@ashishki-desk.ger.corp.intel.com>
Date:	Tue, 18 Feb 2014 14:42:23 +0200
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Matt Fleming <matt.fleming@...el.com>
Subject: Re: [PATCH v1 07/11] x86: perf: intel_pt: Intel PT PMU driver

Peter Zijlstra <peterz@...radead.org> writes:

> On Thu, Feb 06, 2014 at 12:50:30PM +0200, Alexander Shishkin wrote:
>> Add support for Intel Processor Trace (PT) to kernel's perf/itrace events.
>> PT is an extension of Intel Architecture that collects information about
>> software execuction such as control flow, execution modes and timings and
>> formats it into highly compressed binary packets. Even being compressed,
>> these packets are generated at hundreds of megabytes per second per core,
>> which makes it impractical to decode them on the fly in the kernel. Thus,
>> buffers containing this binary stream are zero-copy mapped to the debug
>> tools in userspace for subsequent decoding and analysis.
>> 
>> Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
>> ---
>>  arch/x86/include/uapi/asm/msr-index.h     |  18 +
>>  arch/x86/kernel/cpu/Makefile              |   1 +
>>  arch/x86/kernel/cpu/intel_pt.h            | 127 ++++
>>  arch/x86/kernel/cpu/perf_event.c          |   4 +
>>  arch/x86/kernel/cpu/perf_event_intel.c    |  10 +
>>  arch/x86/kernel/cpu/perf_event_intel_pt.c | 991 ++++++++++++++++++++++++++++++
>>  6 files changed, 1151 insertions(+)
>>  create mode 100644 arch/x86/kernel/cpu/intel_pt.h
>>  create mode 100644 arch/x86/kernel/cpu/perf_event_intel_pt.c
>
> Andi said that when itrace is enabled the LBR is wrecked; this patch
> seems to fail to deal with that.

True, there needs to be a _safe() msr access before any configuration is
done, I have a fix for that, but let's first deal with the buffer
management.

Regards,
--
Alex
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