linux-kernel - Re: [PATCH net-next 1/3] perf: generalize perf

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Message-ID: <20160225164538.GR6356@twins.programming.kicks-ass.net>
Date:	Thu, 25 Feb 2016 17:45:38 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexei Starovoitov <ast@...com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Wang Nan <wangnan0@...wei.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/3] perf: generalize perf_callchain

On Thu, Feb 25, 2016 at 08:37:34AM -0800, Alexei Starovoitov wrote:
> On 2/25/16 6:18 AM, Peter Zijlstra wrote:
> >On Wed, Feb 17, 2016 at 07:58:57PM -0800, Alexei Starovoitov wrote:
> >>. avoid walking the stack when there is no room left in the buffer
> >>. generalize get_perf_callchain() to be called from bpf helper
> >
> >If it does two things it should be two patches.
> 
> could have been two patches, but it will only add more churn
> to the same lines. what's the concern?

It makes review easier, shows which modification is for what purpose.

Also the changelog really needs more; it should for example explain what
BPF needs from the callchain code, and preferably why.