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Re: [PATCH v5 3/5] MIPS: perf: Reorganize contents of perf support files

To: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>, ralf@linux-mips.org
Subject: Re: [PATCH v5 3/5] MIPS: perf: Reorganize contents of perf support files.
From: David Daney <david.s.daney@gmail.com>
Date: Sat, 24 Sep 2011 13:44:00 -0700
Cc: David Daney <david.daney@cavium.com>, linux-mips@linux-mips.org, Peter Zijlstra <a.p.zijlstra@chello.nl>, Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>, Arnaldo Carvalho de Melo <acme@redhat.com>, Dezhong Diao <dediao@cisco.com>, Gabor Juhos <juhosg@openwrt.org>
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On 09/23/2011 07:50 PM, Deng-Cheng Zhu wrote:
2011/9/23 David Daney<david.daney@cavium.com>
The contents of arch/mips/kernel/perf_event.c and
arch/mips/kernel/perf_event_mipsxx.c were divided in a seemingly ad
hoc manner, with the first including the second.

I moved all the hardware counter support code to perf_event_mipsxx.c
and removed the gating #ifdefs to the Kconfig and Makefile.

Now perf_event.c contains only the callchain support, everything else
is in perf_event_mipsxx.c

Sorry for my late comment. I personally don't think it's a bad idea to
use the original gating #ifdefs, because it allows sharing common code
among different types of MIPS PMUs. Also, using CPU types as compiling
conditions seems make sense. If you move the common hunk to
perf_event_mipsxx.c, other CPUs like loognson series will have to duplicate
these stuff.


I disagree, and here is why:

Almost all the the code is mipsxx specific.

If Loongson has a PMU that can reuse this code, it can just be added to perf_event_mipsxx.c along with all the other mips compatible PMUs

If this is not feasible, then it can have its own file and and common code can be removed to a common place at that time.

In any event, I have not seen any Loongson PMU patches, if someone has such patches I would be happy to consider changes that would make the kernel as a whole cleaner. But preventing cleanup and removal of a ton of #ifdefery in hope that Loongson patches may someday want something different is not what I would call a good way forward.

David Daney




Deng-Cheng



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