linux-kernel - Re: [PATCH RESEND] kprobe: Use percpu counter to collect nhit statistics

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Date:	Tue, 9 Feb 2016 11:09:36 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>,
	'Martin KaFai Lau' <kafai@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Josef Bacik <jbacik@...com>, Kernel Team <kernel-team@...com>
Subject: Re: [PATCH RESEND] kprobe: Use percpu counter to collect nhit
 statistics


* Steven Rostedt <rostedt@...dmis.org> wrote:

> On Thu, 4 Feb 2016 10:24:12 +0000
> 平松雅巳 / HIRAMATU，MASAMI <masami.hiramatsu.pt@...achi.com> wrote:
> 
> > From: Martin KaFai Lau [mailto:kafai@...com]
> > >
> > >When doing ebpf+kprobe on some hot TCP functions (e.g.
> > >tcp_rcv_established), the kprobe_dispatcher shows up in 'perf report'.
> > >
> > >In kprobe_dispatcher(), there is a lot of cache bouncing
> > >in 'tk->nhit++'.  'tk->nhit' and 'tk->tp.flags' also share
> > >the same cacheline.
> > >  
> > 
> > Ingo, could you consider to merge this?
> > 
> 
> Ingo, you can also add my
> 
>  Acked-by: Steven Rostedt <rostedt@...dmis.org>

Yeah, nice optimization, picked it up - thanks guys!

	Ingo