linux-kernel - Re: [PATCH v9 14/26] x86/resctrl: Introduce interface to display number of free counters

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Message-ID: <CALPaoCjLn8CZtPjTtd1ojj3RxNwpmmpUD-bb6nfsXcYTezEceQ@mail.gmail.com>
Date: Mon, 4 Nov 2024 15:14:36 +0100
From: Peter Newman <peternewman@...gle.com>
To: Babu Moger <babu.moger@....com>
Cc: corbet@....net, reinette.chatre@...el.com, tglx@...utronix.de, 
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, 
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Subject: Re: [PATCH v9 14/26] x86/resctrl: Introduce interface to display
 number of free counters

Hi Babu,

On Wed, Oct 30, 2024 at 12:24 AM Babu Moger <babu.moger@....com> wrote:
>
> Provide the interface to display the number of free monitoring counters
> available for assignment in each doamin when mbm_cntr_assign is supported.
>
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
> v9: New patch.
> ---
>  Documentation/arch/x86/resctrl.rst     |  4 ++++
>  arch/x86/kernel/cpu/resctrl/monitor.c  |  1 +
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 33 ++++++++++++++++++++++++++
>  3 files changed, 38 insertions(+)
>
> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> index 2f3a86278e84..2bc58d974934 100644
> --- a/Documentation/arch/x86/resctrl.rst
> +++ b/Documentation/arch/x86/resctrl.rst
> @@ -302,6 +302,10 @@ with the following files:
>         memory bandwidth tracking to a single memory bandwidth event per
>         monitoring group.
>
> +"available_mbm_cntrs":
> +       The number of free monitoring counters available assignment in each domain
> +       when the architecture supports mbm_cntr_assign mode.

It seems you need to clarify that counters are only available to a
domain when they're available in all domains:

resctrl# for i in `seq 100`; do
> mkdir mon_groups/m${i}
> done
resctrl# cat info/L3_MON/available_mbm_cntrs
0=0;1=0;2=0;3=0;4=0;5=0;6=0;7=0;8=0;9=0;10=0;11=0;12=0;16=0;17=0;18=0;19=0;20=0;21=0;22=0;23=0;24=0;25=0;26=0;27=0;28=0

resctrl# cd info/L3_MON/
L3_MON# echo '/m1/0=_' > mbm_assign_control
L3_MON# cat available_mbm_cntrs
0=2;1=0;2=0;3=0;4=0;5=0;6=0;7=0;8=0;9=0;10=0;11=0;12=0;16=0;17=0;18=0;19=0;20=0;21=0;22=0;23=0;24=0;25=0;26=0;27=0;28=0
L3_MON# echo '/m16/0+t' > mbm_assign_control
-bash: echo: write error: Invalid argument
L3_MON# cat ../last_cmd_status
Out of MBM assignable counters
Assign operation '+t' failed on the group /m16/

L3_MON# rmdir ../../mon_groups/m1
L3_MON# cat available_mbm_cntrs
0=2;1=2;2=2;3=2;4=2;5=2;6=2;7=2;8=2;9=2;10=2;11=2;12=2;16=2;17=2;18=2;19=2;20=2;21=2;22=2;23=2;24=2;25=2;26=2;27=2;28=2
L3_MON# echo '/m16/0+t' > mbm_assign_control
L3_MON#


-Peter