linux-kernel - Re: [PATCH v5 20/20] x86/resctrl: Introduce interface to modify assignment states of the groups

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Message-ID: <CALPaoCiv9pFg2kzG9i-mVy4D4EP600x38F+WSXR2DqoZ9GjecA@mail.gmail.com>
Date: Thu, 25 Jul 2024 10:11:47 -0700
From: Peter Newman <peternewman@...gle.com>
To: babu.moger@....com
Cc: corbet@....net, fenghua.yu@...el.com, reinette.chatre@...el.com, 
	tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, 
	dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com, 
	paulmck@...nel.org, rdunlap@...radead.org, tj@...nel.org, 
	peterz@...radead.org, yanjiewtw@...il.com, kim.phillips@....com, 
	lukas.bulwahn@...il.com, seanjc@...gle.com, jmattson@...gle.com, 
	leitao@...ian.org, jpoimboe@...nel.org, rick.p.edgecombe@...el.com, 
	kirill.shutemov@...ux.intel.com, jithu.joseph@...el.com, kai.huang@...el.com, 
	kan.liang@...ux.intel.com, daniel.sneddon@...ux.intel.com, 
	pbonzini@...hat.com, sandipan.das@....com, ilpo.jarvinen@...ux.intel.com, 
	maciej.wieczor-retman@...el.com, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, eranian@...gle.com, james.morse@....com
Subject: Re: [PATCH v5 20/20] x86/resctrl: Introduce interface to modify
 assignment states of the groups

Hi Babu,

On Wed, Jul 24, 2024 at 6:23 PM Moger, Babu <bmoger@....com> wrote:
>
> Hi Peter,
>
> On 7/24/2024 7:03 PM, Peter Newman wrote:
> > Hi Babu,
> >
> > On Wed, Jul 3, 2024 at 2:51 PM Babu Moger <babu.moger@....com> wrote:
> >>
> >> Introduce the interface to enable events in ABMC mode.
> >>
> >> Events can be enabled or disabled by writing to file
> >> /sys/fs/resctrl/info/L3_MON/mbm_control
> >>
> >> Format is similar to the list format with addition of op-code for the
> >> assignment operation.
> >>   "<CTRL_MON group>/<MON group>/<op-code><flags>"
> >>
> >> Format for specific type of groups:
> >>
> >>   * Default CTRL_MON group:
> >>           "//<domain_id><op-code><flags>"
> >>
> >>   * Non-default CTRL_MON group:
> >>           "<CTRL_MON group>//<domain_id><op-code><flags>"
> >>
> >>   * Child MON group of default CTRL_MON group:
> >>           "/<MON group>/<domain_id><op-code><flags>"
> >>
> >>   * Child MON group of non-default CTRL_MON group:
> >>           "<CTRL_MON group>/<MON group>/<domain_id><op-code><flags>"
> >
> > Just a reminder, Reinette and I had discussed[1] omitting the
> > domain_id for performing the same operation on all domains.
>
> Yes. I remember. Lets refresh our memory.
> >
> > I would really appreciate this, otherwise our most typical operations
> > could be really tedious and needlessly serialized.
>
> >
> > # cat mbm_control
> > //0=tl;1=tl;2=tl;3=tl;4=tl;5=tl;6=tl;7=tl;8=tl;9=tl;10=tl;11=tl;12=tl;13=tl;14=tl;15=tl;16=tl;17=tl;18=tl;19=tl;20=tl;21=tl;22=tl;23=tl;24=tl;25=tl;26=tl;27=tl;28=tl;29=tl;30=tl;31=tl;
> > # echo '//-l' > mbm_control
>
> What is the expectation here?
> You want to unassign local event on all the domains?

Correct.

>
> Domain id makes it easy to parse the command. Without that it parsing
> code becomes  messy.
>
> How about something like this? We can use the max domain id to mean all
> the domains. In the above case there are 32 domains(0-31). 32 is total
> number of domains. We can get that details looking through all the
> domains. We can print that detail when we list it.

This sounds like only a minor simplification to the parsing code. It
seems like it would be easy to determine if the final '/' is
immediately followed by an opcode (+-=_) rather than a number.

-Peter