linux-kernel - Re: [tip:perf/core] perf/x86: Move perf_event.c ............... => x86/events/core.c

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Message-ID: <20160209140551.GC26641@gmail.com>
Date:	Tue, 9 Feb 2016 15:05:51 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	jolsa@...hat.com, linux-kernel@...r.kernel.org, bp@...e.de,
	a.p.zijlstra@...llo.nl, acme@...hat.com,
	torvalds@...ux-foundation.org, eranian@...gle.com,
	peterz@...radead.org, hpa@...or.com, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/core] perf/x86: Move perf_event.c ............... =>
 x86/events/core.c


* Vince Weaver <vincent.weaver@...ne.edu> wrote:

> On Tue, 9 Feb 2016, tip-bot for Borislav Petkov wrote:
> 
> > Commit-ID:  fa9cbf320e996eaa3d219344b6f7013b096cafd9
> > Gitweb:     http://git.kernel.org/tip/fa9cbf320e996eaa3d219344b6f7013b096cafd9
> > Author:     Borislav Petkov <bp@...e.de>
> > AuthorDate: Mon, 8 Feb 2016 17:09:04 +0100
> > Committer:  Ingo Molnar <mingo@...nel.org>
> > CommitDate: Tue, 9 Feb 2016 10:23:49 +0100
> > 
> > perf/x86: Move perf_event.c ............... => x86/events/core.c
> > 
> > Also, keep the churn at minimum by adjusting the include "perf_event.h"
> > when each file gets moved.
> 
> I have to admit I've been falling behind on my lkml reading, but is there 
> a good reason for moving all these files around?

Yeah, as the PMU drivers grew organically the naming scheme became a bit messy:

 - for example the uncore drivers are under kernel/cpu/, although they are not
   bound to CPUs.

 - separation between various vendor drivers is not always chrystal clear.

 - the 'kernel/' subdirectory is a needless anachronism, we try to move bits out
   of it when the opportunity presents itself.

 - the new naming also better follows the core kernel/events/ perf code.

I presume after this round of patches is in, Boris will send another round to 
reorganize the Intel PMU drivers as well.

> I'm often using "git blame" to track down when bugs are introduced, and it's a 
> big pain trying to do that across file moves like this.  Although that's maybe 
> just due to difficiencies in my git usage skills.

It seems to work reasonably well here:

241771ef016b5 arch/x86/kernel/cpu/perf_counter.c (Ingo Molnar            2008-12-03 10:39:53 +0100    1) /*
cdd6c482c9ff9 arch/x86/kernel/cpu/perf_event.c   (Ingo Molnar            2009-09-21 12:02:48 +0200    2)  * Performance events x86 architecture code
241771ef016b5 arch/x86/kernel/cpu/perf_counter.c (Ingo Molnar            2008-12-03 10:39:53 +0100    3)  *
98144511427c1 arch/x86/kernel/cpu/perf_counter.c (Ingo Molnar            2009-04-29 14:52:50 +0200    4)  *  Copyright (C) 2008 Thomas Gleixner <tglx@...utronix.de>
98144511427c1 arch/x86/kernel/cpu/perf_counter.c (Ingo Molnar            2009-04-29 14:52:50 +0200    5)  *  Copyright (C) 2008-2009 Red Hat, Inc., Ingo Molnar
98144511427c1 arch/x86/kernel/cpu/perf_counter.c (Ingo Molnar            2009-04-29 14:52:50 +0200    6)  *  Copyright (C) 2009 Jaswinder Singh Rajput
98144511427c1 arch/x86/kernel/cpu/perf_counter.c (Ingo Molnar            2009-04-29 14:52:50 +0200    7)  *  Copyright (C) 2009 Advanced Micro Devices, Inc., Robert Richter
90eec103b96e3 arch/x86/kernel/cpu/perf_event.c   (Peter Zijlstra         2015-11-16 11:08:45 +0100    8)  *  Copyright (C) 2008-2009 Red Hat, Inc., Peter Zijlstra
30dd568c91260 arch/x86/kernel/cpu/perf_counter.c (Markus Metzger         2009-07-21 15:56:48 +0200    9)  *  Copyright (C) 2009 Intel Corporation, <markus.t.metzger@...el.com>
1da53e023029c arch/x86/kernel/cpu/perf_event.c   (Stephane Eranian       2010-01-18 10:58:01 +0200   10)  *  Copyright (C) 2009 Google, Inc., Stephane Eranian
241771ef016b5 arch/x86/kernel/cpu/perf_counter.c (Ingo Molnar            2008-12-03 10:39:53 +0100   11)  *
241771ef016b5 arch/x86/kernel/cpu/perf_counter.c (Ingo Molnar            2008-12-03 10:39:53 +0100   12)  *  For licencing details see kernel-base/COPYING
241771ef016b5 arch/x86/kernel/cpu/perf_counter.c (Ingo Molnar            2008-12-03 10:39:53 +0100   13)  */
241771ef016b5 arch/x86/kernel/cpu/perf_counter.c (Ingo Molnar            2008-12-03 10:39:53 +0100   14) 
[...]
c48b60538c3ba arch/x86/kernel/cpu/perf_event.c   (Vince Weaver           2012-03-01 17:28:14 -0500   84)        rdpmcl(hwc->event_base_rdpmc, new_raw_count);

see for example how Git still knows that we had a 
arch/x86/kernel/cpu/perf_counter.c initial file name.

Or how you did an optimization in c48b60538c3ba when the file was already named 
cpu/perf_event.c! :-)

Thanks,

	Ingo