linux-kernel - Re: [PATCH v2 09/23] x86/resctrl: Switch over to the resctrl mbps

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Message-ID: <af0d23a9-61b3-8a2b-7f4c-4d2d6d510238@intel.com>
Date:   Fri, 15 Oct 2021 15:26:50 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     James Morse <james.morse@....com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>
CC:     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>,
        Jamie Iles <jamie@...iainc.com>,
        "D Scott Phillips OS" <scott@...amperecomputing.com>,
        <lcherian@...vell.com>, <bobo.shaobowang@...wei.com>,
        <tan.shaopeng@...itsu.com>
Subject: Re: [PATCH v2 09/23] x86/resctrl: Switch over to the resctrl mbps_val
 list

Hi James,

On 10/1/2021 9:02 AM, James Morse wrote:
> Updates to resctrl's software controller follow the same path as
> other configuration updates, but they don't modify the hardware state.
> rdtgroup_schemata_write() uses parse_line() and the resource's
> ctrlval_parse function to stage the configuration.

parse_ctrlval ?

> resctrl_arch_update_domains() then updates the mbps_val[] array
> instead, and resctrl_arch_update_domains() skips the rdt_ctrl_update()
> call that would update hardware.
> 
> This complicates the interface between resctrl's filesystem parts
> and architecture specific code. It should be possible for mba_sc
> to be completely implemented by the filesystem parts of resctrl. This
> would allow it to work on a second architecture with no additional code.
> 
> Change parse_bw() to write the configuration value directly to the
> mba_sc[] array in the domain structure. Change rdtgroup_schemata_write()

mpbs_val[] array?

> to skip the call to resctrl_arch_update_domains(), meaning all the
> mba_sc specific code in resctrl_arch_update_domains() can be removed.
> On the read-side, show_doms() and update_mba_bw() are changed to read
> the mba_sc[] array from the domain structure. With this,

mbps_val[] ?

Should rdtgroup_size_show() also get a similar snippet?

Reinette