linux-kernel - RE: [patch, resend] x86, perf_counter, bts: optimize BTS overflow handling

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Message-ID: <928CFBE8E7CB0040959E56B4EA41A77EC47B0EC1@irsmsx504.ger.corp.intel.com>
Date:	Tue, 15 Sep 2009 12:35:23 +0100
From:	"Metzger, Markus T" <markus.t.metzger@...el.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	"mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>,
	"markus.t.metzger@...il.com" <markus.t.metzger@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [patch, resend] x86, perf_counter, bts: optimize BTS overflow
 handling

>-----Original Message-----
>From: Peter Zijlstra [mailto:a.p.zijlstra@...llo.nl]
>Sent: Tuesday, September 15, 2009 1:25 PM
>To: Metzger, Markus T
>Cc: mingo@...e.hu; tglx@...utronix.de; hpa@...or.com; markus.t.metzger@...il.com; linux-
>kernel@...r.kernel.org
>Subject: RE: [patch, resend] x86, perf_counter, bts: optimize BTS overflow handling
>
>On Tue, 2009-09-15 at 12:18 +0100, Metzger, Markus T wrote:
>
>> >> Restructure perf_counter sampling into sample creation and sample
>> >> output.
>> >> Prepare a single reference sample for BTS sampling and update the from
>> >> and to address fields when draining the BTS buffer.
>> >> Drain the entire BTS buffer between a single perf_output_begin() /
>> >> perf_output_end() pair.
>> >
>> >Generally looks very nice, one thing though, why did you take regs out
>> >of perf_sample_data, now you get to pass around one extra param..
>>
>>
>> That is to make perf_sample_data describe the sample directly.
>>
>> The regs are used to create the sample; they're not needed once
>> the sample has been created.
>
>True, but I'd have been lazy and not added that extra parameter all over
>the place, but sure ;-)
>
>This is now fast enough to BTS trace the kernel too?

It is. At least on my box.

Once that patch has been accepted, I will ask Ingo to drop
1653192f510bd8114b7b133d7289e6e5c3e95046.

regards,
markus.

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