linux-kernel - RE: [PATCH v11 00/23] x86/resctrl : Support AMD Assignable Bandwidth Monitoring Counters (ABMC)

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Message-ID: <SJ1PR11MB608314CFF36D167483859044FCFA2@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date: Tue, 18 Feb 2025 16:51:22 +0000
From: "Luck, Tony" <tony.luck@...el.com>
To: "babu.moger@....com" <babu.moger@....com>, Peter Newman
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 Stephane" <eranian@...gle.com>
Subject: RE: [PATCH v11 00/23] x86/resctrl : Support AMD Assignable Bandwidth
 Monitoring Counters (ABMC)

> Based on the discussion so far, it felt like it is not a group level
> breakdown. It is kind of global level breakdown. I could be wrong here.
>
> My understanding so far, MPAM has a number of global counters. It can be
> assigned to any domain in the system and monitor events.
>
> They also have a way to configure the events (read, write or both).
>
> Both these feature are inline with current resctrl implementation and can
> be easily adapted.
>
> One thing I am not clear why MPAM implementation plans to create separate
> files(dynamically) in /sys/fs/resctrl/info/L3_MON/ directory to read the
> events. We already have files in each group to read the events.
>
> # ls -l /sys/fs/resctrl/mon_data/mon_L3_00/
> total 0
> -r--r--r--. 1 root root 0 Feb 17 08:16 llc_occupancy
> -r--r--r--. 1 root root 0 Feb 17 08:16 mbm_local_bytes
> -r--r--r--. 1 root root 0 Feb 17 08:16 mbm_total_bytes

It would be nice if the filenames here reflected the reconfigured
events. From what I can tell on AMD with BMEC it is possible to change the
underlying events so that local b/w is reported in the mbm_total_bytes
file, and vice versa. Or an event like:

   6       Dirty Victims from the QOS domain to all types of memory

is counted.

Though maybe we'd need to create a lot of filenames for the 2**6
combinations of bits.

-Tony