linux-kernel - Re: [PATCH v6 42/42] x86/resctrl: Add python script to move resctrl code to /fs/resctrl

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Message-ID: <545e4e79-e309-4bda-9a70-204d83749308@intel.com>
Date: Tue, 25 Feb 2025 08:16:07 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: James Morse <james.morse@....com>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>
CC: 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>,
	"Dave Martin" <dave.martin@....com>, Koba Ko <kobak@...dia.com>, Shanker
 Donthineni <sdonthineni@...dia.com>, Shaopeng Tan
	<tan.shaopeng@...fujitsu.com>, "Tony Luck" <tony.luck@...el.com>
Subject: Re: [PATCH v6 42/42] x86/resctrl: Add python script to move resctrl
 code to /fs/resctrl

Hi James,

On 2/19/25 10:10 PM, Reinette Chatre wrote:
> Hi James,
> 
> On 2/7/25 10:18 AM, James Morse wrote:
>> To support more than one architecture resctrl needs to move from arch/x86
>> to live under fs. Moving all the code breaks any series on the mailing
>> list, so needs scheduling carefully.
>>
>> Maintaining the patch that moves all this code has proved labour intensive.
>> It's also near-impossible to review that no inadvertent changes have
>> crept in.
>>
>> To solve these problems, temporarily add a hacky python program that
>> lists all the functions that should move, and those that should stay.
>>
>> No attempt to parse C code is made, this thing tries to name 'blocks'
>> based on hueristics about the kernel coding style. It's fragile, but
> 
> (heuristics)
> 
>> good enough for its single use here.
>>
>> This only exists to show I have nothing up my sleeve.
>> I don't suggested this gets merged.
>>
>> The patch this script generaets has the following corner cases:
> (generates)
> 
>> * The original files are regenerated, which will add newlines that are
>>   not present in the original file.
>> * An trace-point header file the only contains boiler-plate is created
>>   in the arch and filesystem code. The parser doesn't know how to remove
>>   the includes for these - but its easy to 'keep' the file contents on
>>   the correct side. A follow-up patch will remove these files and their
>>   includes.
> 
> Related to the tracepoints I also noticed that there are some leftover
> tracing defines in files that no longer make use of tracing.
> For example, arch/x86/kernel/cpu/resctrl/monitor.c contains:
> #define CREATE_TRACE_POINTS
> #include monitor_trace.h
> 
> and fs/resctrl/pseudo_lock.c contains:
> #define CREATE_TRACE_POINTS
> #include "pseudo_lock_trace.h"
> 
> I assumed this will also be removed in this follow-up patch?
> 
>> * asm/cpu_device_id.h and a relative path for 'X86_CONFIG()' are kept
>>   in the filesystem code to ensure x86 builds. A follow-up patch will
>>   remove these.
>> * This script doesn't know how to move the documentation, and update the
>>   links in comments. A follow-up patch does this.
> 
> One unexpected thing I noticed is that fs/resctr/internal.h contains:
> #ifndef _ASM_X86_RESCTRL_INTERNAL_H
> #define _ASM_X86_RESCTRL_INTERNAL_H
> ...
> #endif /* _ASM_X86_RESCTRL_INTERNAL_H */

It looks like another item for this list of "corner cases" is that the
#include of all files need to be reviewed after the code move. There are
functions depending on a particular #include that are moved out of the .c
file but the (no longer needed) #include remains.

Reinette