linux-kernel - Re: [PATCH v4 7/7] x86/resctrl: Add debug files when mounted with debug option

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Date:   Thu, 20 Apr 2023 11:59:13 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     "Moger, Babu" <babu.moger@....com>
cc:     corbet@....net, Reinette Chatre <reinette.chatre@...el.com>,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        fenghua.yu@...el.com, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, paulmck@...nel.org, akpm@...ux-foundation.org,
        quic_neeraju@...cinc.com, rdunlap@...radead.org,
        damien.lemoal@...nsource.wdc.com, songmuchun@...edance.com,
        peterz@...radead.org, jpoimboe@...nel.org, pbonzini@...hat.com,
        chang.seok.bae@...el.com, pawan.kumar.gupta@...ux.intel.com,
        jmattson@...gle.com, daniel.sneddon@...ux.intel.com,
        sandipan.das@....com, tony.luck@...el.com, james.morse@....com,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        bagasdotme@...il.com, eranian@...gle.com,
        christophe.leroy@...roup.eu, jarkko@...nel.org,
        adrian.hunter@...el.com, quic_jiles@...cinc.com,
        peternewman@...gle.com
Subject: Re: [PATCH v4 7/7] x86/resctrl: Add debug files when mounted with
 debug option

On Wed, 19 Apr 2023, Moger, Babu wrote:

> 
> 
> On 4/19/23 08:20, Ilpo Järvinen wrote:
> > On Mon, 17 Apr 2023, Babu Moger wrote:
> > 
> >> Add the debug files to the resctrl hierarchy.
> >>
> >> Signed-off-by: Babu Moger <babu.moger@....com>
> >> ---
> >>  arch/x86/kernel/cpu/resctrl/internal.h |    1 +
> >>  arch/x86/kernel/cpu/resctrl/rdtgroup.c |   54 +++++++++++++++++++++++++++++++-
> >>  2 files changed, 54 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> >> index 1eac07ebc31b..855109abb480 100644
> >> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> >> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> >> @@ -288,6 +288,7 @@ struct rdtgroup {
> >>  #define RFTYPE_TOP			BIT(4)
> >>  #define RFTYPE_RES_CACHE		BIT(5)
> >>  #define RFTYPE_RES_MB			BIT(6)
> >> +#define RFTYPE_DEBUG			BIT(7)
> >>  #define RFTYPE_CTRL_INFO		(RFTYPE_INFO | RFTYPE_CTRL)
> >>  #define RFTYPE_MON_INFO			(RFTYPE_INFO | RFTYPE_MON)
> >>  #define RFTYPE_TOP_INFO			(RFTYPE_INFO | RFTYPE_TOP)
> >> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> >> index 15ded0dd5b09..1ec4359348c2 100644
> >> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> >> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> >> @@ -1880,6 +1880,7 @@ static struct rftype res_common_files[] = {
> >>  		.mode		= 0444,
> >>  		.kf_ops		= &rdtgroup_kf_single_ops,
> >>  		.seq_show	= rdtgroup_rmid_show,
> >> +		.fflags		= RFTYPE_BASE | RFTYPE_DEBUG,
> >>  	},
> >>  	{
> >>  		.name		= "schemata",
> >> @@ -1909,6 +1910,7 @@ static struct rftype res_common_files[] = {
> >>  		.mode		= 0444,
> >>  		.kf_ops		= &rdtgroup_kf_single_ops,
> >>  		.seq_show	= rdtgroup_closid_show,
> >> +		.fflags		= RFTYPE_CTRL_BASE | RFTYPE_DEBUG,
> >>  	},
> >>  
> >>  };
> >> @@ -2420,6 +2422,49 @@ static int mkdir_mondata_all(struct kernfs_node *parent_kn,
> >>  			     struct rdtgroup *prgrp,
> >>  			     struct kernfs_node **mon_data_kn);
> >>  
> >> +static void resctrl_add_debug_files(void)
> >> +{
> >> +	struct rftype *rfts, *rft;
> >> +	int len;
> >> +
> >> +	rfts = res_common_files;
> >> +	len = ARRAY_SIZE(res_common_files);
> >> +
> >> +	lockdep_assert_held(&rdtgroup_mutex);
> >> +
> >> +	for (rft = rfts; rft < rfts + len; rft++) {
> >> +		if (rft->fflags & RFTYPE_DEBUG) {
> >> +			rft->fflags &= ~RFTYPE_DEBUG;
> > 
> > I don't fully follow why you need to play with ->fflags like this.
> > 
> > Is it for the ->fflags test in rdtgroup_add_files()? Can't you just do 
> > some extra masking there for RFTYPE_DEBUG based on resctrl_debug which 
> > you already keep?
> 
> Actually with this change, I can remove all these tricks here.
> I don't have to change the check "if (rft->fflags && ((fflags &
> rft->fflags) == rft->fflags)) {"
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 1ec4359348c2..b560c44817bb 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1925,6 +1925,9 @@ static int rdtgroup_add_files(struct kernfs_node
> *kn, unsigned long fflags)
> 
>         lockdep_assert_held(&rdtgroup_mutex);
> 
> +       if (resctrl_debug)
> +               fflags |= RFTYPE_DEBUG;

Yes, looks good.

It matches to the idea I had in my mind but doesn't require putting it 
into the if condition itself.

> +
>         for (rft = rfts; rft < rfts + len; rft++) {
>                 if (rft->fflags && ((fflags & rft->fflags) == rft->fflags)) {
>                         ret = rdtgroup_add_file(kn, rft);
> 
> 
> > 
> >> +			rdtgroup_add_file(rdtgroup_default.kn, rft);
> >> +		}
> >> +	}


-- 
 i.