linux-kernel - Re: [PATCH v1 31/31] x86/resctrl: Move the resctrl filesystem code to /fs/resctrl

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Message-ID: <ZhlfaHhIXe9ZLXmK@e133380.arm.com>
Date: Fri, 12 Apr 2024 17:20:56 +0100
From: Dave Martin <Dave.Martin@....com>
To: Reinette Chatre <reinette.chatre@...el.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>, James Morse <james.morse@....com>,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	H Peter Anvin <hpa@...or.com>, Babu Moger <Babu.Moger@....com>,
	shameerali.kolothum.thodi@...wei.com,
	D Scott Phillips OS <scott@...amperecomputing.com>,
	carl@...amperecomputing.com, lcherian@...vell.com,
	bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
	baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
	Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
	dfustini@...libre.com, amitsinght@...vell.com,
	David Hildenbrand <david@...hat.com>,
	Rex Nie <rex.nie@...uarmicro.com>
Subject: Re: [PATCH v1 31/31] x86/resctrl: Move the resctrl filesystem code
 to /fs/resctrl

On Thu, Apr 11, 2024 at 10:45:01AM -0700, Reinette Chatre wrote:
> Hi Dave,
> 
> On 4/11/2024 7:30 AM, Dave Martin wrote:
> > On Tue, Mar 26, 2024 at 12:44:26PM -0700, Fenghua Yu wrote:
> >> Hi, James,
> >>
> >> On 3/21/24 09:51, James Morse wrote:
> >>> resctrl is linux's defacto interface for managing cache and bandwidth
> >>> policies for groups of tasks.
> >>>
> >>> To allow other architectures to make use of this pseudo filesystem,
> >>> move it live in /fs/resctrl instead of /arch/x86.
> >>>
> >>> This move leaves behind the parts of resctrl that form the architecture
> >>> interface for x86.
> >>>
> >>> Signed-off-by: James Morse <james.morse@....com>
> >>> ---
> >>> Discussion needed on how/when to merge this, as it would conflict with
> >>> all outstanding series. It's probably worth deferring to some opportune
> >>> time, but is included here for illustration.
> >>> ---
> >>>   arch/x86/kernel/cpu/resctrl/core.c        |   15 -
> >>>   arch/x86/kernel/cpu/resctrl/ctrlmondata.c |  505 ---
> >>>   arch/x86/kernel/cpu/resctrl/internal.h    |  310 --
> >>>   arch/x86/kernel/cpu/resctrl/monitor.c     |  821 -----
> >>>   arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 1093 ------
> >>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c    | 3994 --------------------
> >>>   fs/resctrl/ctrlmondata.c                  |  527 +++
> >>>   fs/resctrl/internal.h                     |  340 ++
> >>>   fs/resctrl/monitor.c                      |  843 +++++
> >>>   fs/resctrl/psuedo_lock.c                  | 1122 ++++++
> >>>   fs/resctrl/rdtgroup.c                     | 4013 +++++++++++++++++++++
> >>>   11 files changed, 6845 insertions(+), 6738 deletions(-)
> >>>
> >>
> >> checkpatch reports warnings and checks on this patch. Please fix them. e.g.
> >>
> >> CHECK: Blank lines aren't necessary before a close brace '}'
> >> #13340: FILE: fs/resctrl/rdtgroup.c:3184:
> >> +
> >> +	}
> > 
> > Thanks for spotting these...
> > 
> > However, this is a "move code around with no functional change" patch,
> > so I think that it should paste the original code across verbatim
> > without trying to address style violations.  (Otherwise, there is no
> > hope of checking whether this patch is correct or not...)
> 
> I agree that this patch is too big for it to do more than just move
> code (please see next comments though).
> 
> > 
> > For the above example, see:
> > 47820e73f5b3 ("x86/resctrl: Initialize a new resource group with default MBA values")
> > 
> > Other than code that is moved or cloned from previously existing code,
> > do you see any new style problems actually introduced by this patch?
> > 
> > 
> > Notwithstanding the above, this series will conflict with a lot of the
> > in-flight changes pending for resctrl, so it could be a good opportunity
> > to fix some legacy style nits.
> > 
> > Reinette, do you have a view on this?  If legacy style problems get
> > addressed in the moved code, are they essential for this series or could
> > that be done in a follow-up?
> 
> On its path upstream this series will be scrutinized by various checkers and 
> to ensure a smooth merge I would like to recommend that this series aim to
> get as clean slate as possible from the basic checkers.
> 
> Could a patch addressing these legacy issues precede this patch instead?
> 
> I do not think all need to be addressed though. Some of the spelling warnings
> are false positives and the camel case appears to be the custom for filesystem
> parameter code.
> 
> It is not obvious to me that all are legacy issues though ... could you
> take a second look at the "WARNING: Use #include <linux/resctrl.h>
> instead of <asm/resctrl.h>" ones?
> 
> Reinette

Ack, that does make sense, and it's probably better than letting the dust
settle on this series before applying further cleanups.

I'll make a note to review.

Some of the #include <asm/*> look to have been inherited from the
previous x86 arch code where they would have been more appropriate, but
perhaps some can change to <linux/*> now that more of the definitions
are in the common headers.

Cheers
---Dave