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

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Message-ID: <20160225164847.GT6356@twins.programming.kicks-ass.net>
Date:	Thu, 25 Feb 2016 17:48:47 +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:

> >>  arch/x86/include/asm/stacktrace.h |  2 +-
> >>  arch/x86/kernel/cpu/perf_event.c  |  4 ++--
> >>  arch/x86/kernel/dumpstack.c       |  6 ++++--
> >>  arch/x86/kernel/stacktrace.c      | 18 +++++++++++-------
> >>  arch/x86/oprofile/backtrace.c     |  3 ++-
> >>  include/linux/perf_event.h        | 13 +++++++++++--
> >>  kernel/events/callchain.c         | 32 ++++++++++++++++++++------------
> >>  kernel/events/internal.h          |  2 --
> >>  8 files changed, 51 insertions(+), 29 deletions(-)
> >
> >And at the very least this should have had a note that it doesn't break
> >all the other archs that implement perf-callchain stuff.
> 
> the cross-arch interface is two weak functions
> perf_callchain_kernel() and perf_callchain_user()
> and back into generic via perf_callchain_store().
> Nothing changes there. The code speaks for itself.
> "non-x86 archs are not broken" would be a silly comment.

No, a diffstat like that immediately makes me wonder if you've even
bothered looking at !x86.

A statement to this effect would've shown you did indeed consider it.