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

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Date:	Tue, 15 Sep 2009 13:12:25 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Markus Metzger <markus.t.metzger@...el.com>
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

Totally missed the first one, sorry for that :/

On Tue, 2009-09-15 at 13:00 +0200, Markus Metzger wrote:
> Draining the BTS buffer on a buffer overflow interrupt takes too long
> resulting in a kernel lockup when tracing the kernel.
> 
> 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..

> CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Signed-off-by: Markus Metzger <markus.t.metzger@...el.com>
> ---
>  arch/x86/kernel/cpu/perf_counter.c |   60 	37 +	23 -	0 !
>  include/linux/perf_counter.h       |   68 	64 +	4 -	0 !
>  kernel/perf_counter.c              |  306 	161 +	145 -	0 !
>  3 files changed, 262 insertions(+), 172 deletions(-)

What is that diffstat thing? I always get things like:

 kernel/sched.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)


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