linux-kernel - [PATCH v6 3/3] x86/resctrl: Add new "mba_MBps

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Message-ID: <20231207195613.153980-4-tony.luck@intel.com>
Date:   Thu,  7 Dec 2023 11:56:13 -0800
From:   Tony Luck <tony.luck@...el.com>
To:     Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Peter Newman <peternewman@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <skhan@...uxfoundation.org>, x86@...nel.org
Cc:     Shaopeng Tan <tan.shaopeng@...itsu.com>,
        James Morse <james.morse@....com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Babu Moger <babu.moger@....com>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        patches@...ts.linux.dev, Tony Luck <tony.luck@...el.com>
Subject: [PATCH v6 3/3] x86/resctrl: Add new "mba_MBps_event" mount option to documentation

New mount option may be used to choose a specific memory bandwidth
monitoring event to feed the MBA Software Controller(mba_sc) feedback
loop.

Signed-off-by: Tony Luck <tony.luck@...el.com>
---
 Documentation/arch/x86/resctrl.rst | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index a6279df64a9d..a0c521db6786 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -35,7 +35,8 @@ about the feature from resctrl's info directory.
 
 To use the feature mount the file system::
 
- # mount -t resctrl resctrl [-o cdp[,cdpl2][,mba_MBps][,debug]] /sys/fs/resctrl
+ # mount -t resctrl resctrl [-o cdp[,cdpl2][,mba_MBps] \
+ [,mba_MBps_event=[mbm_local_bytes|mbm_total_bytes]][,debug]] /sys/fs/resctrl
 
 mount options are:
 
@@ -45,7 +46,12 @@ mount options are:
 	Enable code/data prioritization in L2 cache allocations.
 "mba_MBps":
 	Enable the MBA Software Controller(mba_sc) to specify MBA
-	bandwidth in MBps
+	bandwidth in MBps. Defaults to using MBM local bandwidth,
+	but will use total bandwidth on systems that do not support
+	local bandwidth monitoring.
+"mba_MBps_event=[mbm_local_bytes|mbm_total_bytes]":
+	Enable the MBA Software Controller(mba_sc) with a specific
+	MBM event as input to the feedback loop.
 "debug":
 	Make debug files accessible. Available debug files are annotated with
 	"Available only with debug option".
@@ -538,6 +544,12 @@ where as user can switch to the "MBA software controller" mode using
 a mount option 'mba_MBps'. The schemata format is specified in the below
 sections.
 
+By default the software feedback mechanism uses measurement of local
+memory bandwidth to make adjustments to throttling levels. If a system
+is running applications with poor NUMA locality users may want to use
+the "mba_MBps_event=mbm_total_bytes" mount option which will use total
+memory bandwidth measurements instead of local.
+
 L3 schemata file details (code and data prioritization disabled)
 ----------------------------------------------------------------
 With CDP disabled the L3 schemata format is::
-- 
2.41.0