From aaa5fa35743ab9f0726568611a85e3e15349b9bf Mon Sep 17 00:00:00 2001
From: Fenghua Yu <fenghua.yu@intel.com>
Date: Tue, 10 Oct 2023 12:42:39 +0200
Subject: [PATCH] Documentation/x86: Document resctrl's new sparse_masks
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The documentation mentions that non-contiguous bit masks are not
supported in Intel Cache Allocation Technology (CAT).
Update the documentation on how to determine if sparse bit masks are
allowed in L2 and L3 CAT.
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Peter Newman <peternewman@google.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Peter Newman <peternewman@google.com>
Link: https://lore.kernel.org/r/3e9610997164f648e15c5c2e90d4944ce36504fe.1696934091.git.maciej.wieczor-retman@intel.com
---
Documentation/arch/x86/resctrl.rst | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index cb05d90111b4f..4c6421e2aa31c 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -124,6 +124,13 @@ related to allocation:
"P":
Corresponding region is pseudo-locked. No
sharing allowed.
+"sparse_masks":
+ Indicates if non-contiguous 1s value in CBM is supported.
+
+ "0":
+ Only contiguous 1s value in CBM is supported.
+ "1":
+ Non-contiguous 1s value in CBM is supported.
Memory bandwidth(MB) subdirectory contains the following files
with respect to allocation:
@@ -445,12 +452,13 @@ For cache resources we describe the portion of the cache that is available
for allocation using a bitmask. The maximum value of the mask is defined
by each cpu model (and may be different for different cache levels). It
is found using CPUID, but is also provided in the "info" directory of
-the resctrl file system in "info/{resource}/cbm_mask". Intel hardware
+the resctrl file system in "info/{resource}/cbm_mask". Some Intel hardware
requires that these masks have all the '1' bits in a contiguous block. So
0x3, 0x6 and 0xC are legal 4-bit masks with two bits set, but 0x5, 0x9
-and 0xA are not. On a system with a 20-bit mask each bit represents 5%
-of the capacity of the cache. You could partition the cache into four
-equal parts with masks: 0x1f, 0x3e0, 0x7c00, 0xf8000.
+and 0xA are not. Check /sys/fs/resctrl/info/{resource}/sparse_masks
+if non-contiguous 1s value is supported. On a system with a 20-bit mask
+each bit represents 5% of the capacity of the cache. You could partition
+the cache into four equal parts with masks: 0x1f, 0x3e0, 0x7c00, 0xf8000.
Memory bandwidth Allocation and monitoring
==========================================
--
GitLab