linux-kernel - Re: [PATCH v11 0/8] x86/resctrl: mba

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Message-ID: <7e7c01c5-f64f-42c3-9364-ddcfd01b25c1@intel.com>
Date: Mon, 9 Dec 2024 09:10:20 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>, "Peter
 Newman" <peternewman@...gle.com>, Jonathan Corbet <corbet@....net>,
	<x86@...nel.org>, Borislav Petkov <bp@...en8.de>
CC: James Morse <james.morse@....com>, Jamie Iles <quic_jiles@...cinc.com>,
	Babu Moger <babu.moger@....com>, Randy Dunlap <rdunlap@...radead.org>,
	"Shaopeng Tan (Fujitsu)" <tan.shaopeng@...itsu.com>,
	<linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
	<patches@...ts.linux.dev>
Subject: Re: [PATCH v11 0/8] x86/resctrl: mba_MBps enhancement

Hi Boris,

On 12/6/24 8:31 AM, Tony Luck wrote:
> Background
> ----------
> 
> The resctrl filesystem supports a mount option that allows users to
> specify a memory bandwidth limit in MiB/s for each domain of a CTRL_MON
> group.  The underlying implementation uses data collected from the local
> memory bandwidth monitoring event for the CTRL_MON group and all of
> its MON subgroups as input to a feedback loop that adjusts the memory
> bandwidth allocation control percentage up or down to keep the group
> within the limit set by the user.
> 
> Problem statement
> -----------------
> 
> Hard coding the local memory bandwidth monitoring event has the following
> issues:
> 
> 1) Some systems may support total memory bandwidth monitoring but
> not local.  The user cannot use this mount option on such systems.
> 
> 2) For large workloads that span NUMA domains using local bandwidth
> monitoring will not throttle jobs correctly.
> 
> 3) Users may have a mix of large and small workloads and may want to
> use different input events per CTRL_MON group.
> 
> Solution
> --------
> 
> A) Provide a new user interface to choose which event is used for each
>    CTRL_MON group.
> 
> B) Allow systems that only support total memory bandwidth monitoring to
>    use total bandwidth event.
> 
> Changes since v10:
> Link: https://lore.kernel.org/all/20241122235832.27498-1-tony.luck@intel.com/
> 
> Patch	Change
> -----	------
> 
> 2	s/filesystm/filesystem/
> 	Reformat block comment above definition of mba_mbps_default_event using
> 	more of 80 column width
> 
> 3	s/Update_mba_bw()/update_mba_bw()
> 
> Added Reinette's Reviewed-by tag to parts 2-8


Could you please consider this series for inclusion?

> 
> N.B. v6.13-rc1 introduced a locking change in commit f1be1788a32e ("block:
> model freeze & enter queue as lock for supporting lockdep") that throws
> a lockdep splat when mounting the resctrl filesystem (with certain
> CONFIG options).
> 
> Proposed patches that fix this are here:
> Link: https://lore.kernel.org/all/20241206111611.978870-2-ming.lei@redhat.com/
> Link: https://lore.kernel.org/all/20241206111611.978870-3-ming.lei@redhat.com/
> 
> 
This fix has been merged into v6.13-rc2.

Thank you very much.

Reinette