linux-kernel - Re: [PATCH v1 30/31] x86/resctrl: Move the filesystem bits to headers visible to fs/resctrl

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Message-ID: <Zh/f6Kv1oWTRPna3@e133380.arm.com>
Date: Wed, 17 Apr 2024 15:42:48 +0100
From: Dave Martin <Dave.Martin@....com>
To: Reinette Chatre <reinette.chatre@...el.com>
Cc: James Morse <james.morse@....com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Fenghua Yu <fenghua.yu@...el.com>,
	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 30/31] x86/resctrl: Move the filesystem bits to
 headers visible to fs/resctrl

On Mon, Apr 15, 2024 at 11:03:32AM -0700, Reinette Chatre wrote:
> Hi Dave,
> 
> On 4/12/2024 9:20 AM, Dave Martin wrote:
> > On Thu, Apr 11, 2024 at 10:43:55AM -0700, Reinette Chatre wrote:
> >> Hi Dave,
> >>
> >> On 4/11/2024 7:28 AM, Dave Martin wrote:
> >>> On Mon, Apr 08, 2024 at 08:42:00PM -0700, Reinette Chatre wrote:
> >>>> Hi James,
> >>>>
> >>>> On 3/21/2024 9:51 AM, James Morse wrote:
> >>>> ..
> >>>>> diff --git a/include/linux/resctrl_types.h b/include/linux/resctrl_types.h
> >>>>> index 4788bd95dac6..fe0b10b589c0 100644
> >>>>> --- a/include/linux/resctrl_types.h
> >>>>> +++ b/include/linux/resctrl_types.h
> >>>>> @@ -7,6 +7,36 @@
> >>>>>  #ifndef __LINUX_RESCTRL_TYPES_H
> >>>>>  #define __LINUX_RESCTRL_TYPES_H
> >>>>>  
> >>>>> +#define CQM_LIMBOCHECK_INTERVAL	1000
> >>>>> +
> >>>>> +#define MBM_CNTR_WIDTH_BASE		24
> >>>>> +#define MBM_OVERFLOW_INTERVAL		1000
> >>>>> +#define MAX_MBA_BW			100u
> >>>>> +#define MBA_IS_LINEAR			0x4
> >>>>> +
> >>>>> +/* rdtgroup.flags */
> >>>>> +#define	RDT_DELETED		1
> >>>>> +
> >>>>> +/* rftype.flags */
> >>>>> +#define RFTYPE_FLAGS_CPUS_LIST	1
> >>>>> +
> >>>>> +/*
> >>>>> + * Define the file type flags for base and info directories.
> >>>>> + */
> >>>>> +#define RFTYPE_INFO			BIT(0)
> >>>>> +#define RFTYPE_BASE			BIT(1)
> >>>>> +#define RFTYPE_CTRL			BIT(4)
> >>>>> +#define RFTYPE_MON			BIT(5)
> >>>>> +#define RFTYPE_TOP			BIT(6)
> >>>>> +#define RFTYPE_RES_CACHE		BIT(8)
> >>>>> +#define RFTYPE_RES_MB			BIT(9)
> >>>>> +#define RFTYPE_DEBUG			BIT(10)
> >>>>> +#define RFTYPE_CTRL_INFO		(RFTYPE_INFO | RFTYPE_CTRL)
> >>>>> +#define RFTYPE_MON_INFO			(RFTYPE_INFO | RFTYPE_MON)
> >>>>> +#define RFTYPE_TOP_INFO			(RFTYPE_INFO | RFTYPE_TOP)
> >>>>> +#define RFTYPE_CTRL_BASE		(RFTYPE_BASE | RFTYPE_CTRL)
> >>>>> +#define RFTYPE_MON_BASE			(RFTYPE_BASE | RFTYPE_MON)
> >>>>> +
> >>>>>  /* Reads to Local DRAM Memory */
> >>>>>  #define READS_TO_LOCAL_MEM		BIT(0)
> >>>>>  
> >>>>
> >>>> Not all these new seem to belong in this file. Could you please confirm?
> >>>>
> >>>> For example:
> >>>> Earlier in series it was mentioned that struct rdtgroup is private to the
> >>>> fs so having RDT_DELETED is unexpected as it implies access to struct rdtgroup.
> >>>>
> >>>> CQM_LIMBOCHECK_INTERVAL seems private to the fs code, so too
> >>>> RFTYPE_FLAGS_CPUS_LIST.
> >>>>
> >>>> Reinette
> >>>>
> >>>
> >>> I'll flag this for James to review.
> >>>
> >>> These have to be moved out of the x86 private headers, but you're right
> >>> that some of them seem logically private to the resctrl core.
> >>>
> >>> I guess some of these could move to fs/resctrl/internal.h?
> >>
> >> It looks to me that way.
> >>
> >>>
> >>> OTOH, might it be preferable to keep all the flag definitions for a
> >>> given member together for ease of maintenance, even if some are for
> >>> resctrl internal use only?
> >>
> >> Indeed, those RFTYPE flags really seem to be fs code but I agree that
> >> architectures' use of RFTYPE_RES_CACHE and RFTYPE_RES_MB does make this
> >> complicated and having these in a central place is reasonable to me.
> >>
> >> Reinette
> > 
> > Maybe we could split these into two groups, and clearly comment the ones
> > that have no user outside resctrl as internal use only?
> 
> Another option to consider, which I think you hinted about earlier, is
> to add an enum that maps to the RFTYPE_RES_CACHE and RFTYPE_RES_MB
> flags. Just like, for example, RDTCTRL_GROUP maps to RFTYPE_CTRL.
> The new enum can then be used similar to enum rdt_group_type to pick the
> appropriate files based on RFTYPE_RES_CACHE or RFTYPE_RES_MB. 
> 
> > 
> > That's not as clean as removing those definitions from a shared header,
> > but at least would help document the issue until/unless a better
> > solution is found...
> > 
> > Cheers
> > ---Dave

(Note, I seem to have responded to that suggestion via my reply on patch 3,
rather than here:

"x86/resctrl: Move ctrlval string parsing policy away from the arch code"
https://lore.kernel.org/lkml/Zh6kRMkqVpu0Km4l@e133380.arm.com/ )

Cheers
---Dave