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Message-ID: <16cebf7069e11e07c0d9e343aa72363325befafd.1749677012.git.babu.moger@amd.com>
Date: Wed, 11 Jun 2025 16:23:31 -0500
From: Babu Moger <babu.moger@....com>
To: <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
<reinette.chatre@...el.com>, <Dave.Martin@....com>, <james.morse@....com>,
<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <akpm@...ux-foundation.org>,
<paulmck@...nel.org>, <rostedt@...dmis.org>, <thuth@...hat.com>,
<ardb@...nel.org>, <gregkh@...uxfoundation.org>, <seanjc@...gle.com>,
<thomas.lendacky@....com>, <pawan.kumar.gupta@...ux.intel.com>,
<perry.yuan@....com>, <yosry.ahmed@...ux.dev>, <kai.huang@...el.com>,
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<mario.limonciello@....com>, <xin3.li@...el.com>, <sohil.mehta@...el.com>,
<chang.seok.bae@...el.com>, <andrew.cooper3@...rix.com>,
<ebiggers@...gle.com>, <ak@...ux.intel.com>, <xin@...or.com>,
<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v6 6/8] fs/resctrl: Introduce interface to display io_alloc CBMs
The io_alloc feature in resctrl enables system software to configure
the portion of the L3 cache allocated for I/O traffic.
Add the interface to display CBMs (Capacity Bit Mask) of io_alloc
feature.
The CBM interface file io_alloc_cbm will reside in the info directory
(e.g., /sys/fs/resctrl/info/L3/). Displaying the resource name is not
necessary. Pass the resource name to show_doms() and print it only if
the name is valid. For io_alloc, pass NULL to suppress printing the
resource name.
When CDP is enabled, io_alloc routes traffic using the highest CLOSID
associated with an L3CODE resource. However, CBMs can be accessed via
either L3CODE or L3DATA resources.
Signed-off-by: Babu Moger <babu.moger@....com>
---
v6: Added "io_alloc_cbm" details in user doc resctrl.rst.
Resource name is not printed in CBM now. Corrected the texts about it
in resctrl.rst.
v5: Resolved conflicts due to recent resctrl FS/ARCH code restructure.
Updated show_doms() to print the resource if only it is valid. Pass NULL while
printing io_alloc CBM.
Changed the code to access the CBMs via either L3CODE or L3DATA resources.
v4: Updated the change log.
Added rdtgroup_mutex before rdt_last_cmd_puts().
Returned -ENODEV when resource type is CDP_DATA.
Kept the resource name while printing the CBM (L3:0=fff) that way
I dont have to change show_doms() just for this feature and it is
consistant across all the schemata display.
v3: Minor changes due to changes in resctrl_arch_get_io_alloc_enabled()
and resctrl_io_alloc_closid_get().
Added the check to verify CDP resource type.
Updated the commit log.
v2: Fixed to display only on L3 resources.
Added the locks while processing.
Rename the displat to io_alloc_cbm (from sdciae_cmd).
---
Documentation/filesystems/resctrl.rst | 13 +++++++
fs/resctrl/ctrlmondata.c | 8 +++--
fs/resctrl/internal.h | 2 ++
fs/resctrl/rdtgroup.c | 51 ++++++++++++++++++++++++++-
4 files changed, 70 insertions(+), 4 deletions(-)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 03c829b2c276..b31748ec8c61 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -169,6 +169,19 @@ related to allocation:
When CDP is enabled, io_alloc routes I/O traffic using the highest
CLOSID allocated for the instruction cache (L3CODE).
+"io_alloc_cbm":
+ Capacity Bit Masks (CBMs) available to supported IO devices which
+ can directly insert cache lines in L3 which can help to reduce the
+ latency. CBMs are displayed in the following format:
+
+ <cache_id0>=<cbm>;<cache_id1>=<cbm>;...
+
+ Example::
+
+ # cat /sys/fs/resctrl/info/L3/io_alloc_cbm
+ 0=ffff;1=ffff
+
+
Memory bandwidth(MB) subdirectory contains the following files
with respect to allocation:
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index 6ed2dfd4dbbd..ea039852569a 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -381,7 +381,8 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
return ret ?: nbytes;
}
-static void show_doms(struct seq_file *s, struct resctrl_schema *schema, int closid)
+void show_doms(struct seq_file *s, struct resctrl_schema *schema, char *resource_name,
+ int closid)
{
struct rdt_resource *r = schema->res;
struct rdt_ctrl_domain *dom;
@@ -391,7 +392,8 @@ static void show_doms(struct seq_file *s, struct resctrl_schema *schema, int clo
/* Walking r->domains, ensure it can't race with cpuhp */
lockdep_assert_cpus_held();
- seq_printf(s, "%*s:", max_name_width, schema->name);
+ if (resource_name)
+ seq_printf(s, "%*s:", max_name_width, resource_name);
list_for_each_entry(dom, &r->ctrl_domains, hdr.list) {
if (sep)
seq_puts(s, ";");
@@ -437,7 +439,7 @@ int rdtgroup_schemata_show(struct kernfs_open_file *of,
closid = rdtgrp->closid;
list_for_each_entry(schema, &resctrl_schema_all, list) {
if (closid < schema->num_closid)
- show_doms(s, schema, closid);
+ show_doms(s, schema, schema->name, closid);
}
}
} else {
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index 9a8cf6f11151..14f3697c1187 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -374,6 +374,8 @@ void rdt_staged_configs_clear(void);
bool closid_allocated(unsigned int closid);
int resctrl_find_cleanest_closid(void);
+void show_doms(struct seq_file *s, struct resctrl_schema *schema,
+ char *name, int closid);
#ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index bbc032b4d0e9..0c2d2cf4baa1 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1997,6 +1997,46 @@ static ssize_t resctrl_io_alloc_write(struct kernfs_open_file *of, char *buf,
return ret ?: nbytes;
}
+static int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of,
+ struct seq_file *seq, void *v)
+{
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
+ struct rdt_resource *r = s->res;
+ u32 io_alloc_closid;
+ int ret = 0;
+
+ cpus_read_lock();
+ mutex_lock(&rdtgroup_mutex);
+
+ rdt_last_cmd_clear();
+
+ if (!r->cache.io_alloc_capable) {
+ rdt_last_cmd_puts("io_alloc feature is not supported on the resource\n");
+ ret = -ENODEV;
+ goto cbm_show_out;
+ }
+
+ if (!resctrl_arch_get_io_alloc_enabled(r)) {
+ rdt_last_cmd_puts("io_alloc feature is not enabled\n");
+ ret = -EINVAL;
+ goto cbm_show_out;
+ }
+
+ io_alloc_closid = resctrl_io_alloc_closid_get(r);
+ if (io_alloc_closid < 0) {
+ rdt_last_cmd_puts("Max CLOSID to support io_alloc is not available\n");
+ ret = -EINVAL;
+ goto cbm_show_out;
+ }
+
+ show_doms(seq, resctrl_schema_io_alloc(s), NULL, io_alloc_closid);
+
+cbm_show_out:
+ mutex_unlock(&rdtgroup_mutex);
+ cpus_read_unlock();
+ return ret;
+}
+
/* rdtgroup information files for one cache resource. */
static struct rftype res_common_files[] = {
{
@@ -2156,6 +2196,12 @@ static struct rftype res_common_files[] = {
.seq_show = resctrl_io_alloc_show,
.write = resctrl_io_alloc_write,
},
+ {
+ .name = "io_alloc_cbm",
+ .mode = 0444,
+ .kf_ops = &rdtgroup_kf_single_ops,
+ .seq_show = resctrl_io_alloc_cbm_show,
+ },
{
.name = "mba_MBps_event",
.mode = 0644,
@@ -2267,9 +2313,12 @@ static void io_alloc_init(void)
{
struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
- if (r->cache.io_alloc_capable)
+ if (r->cache.io_alloc_capable) {
resctrl_file_fflags_init("io_alloc",
RFTYPE_CTRL_INFO | RFTYPE_RES_CACHE);
+ resctrl_file_fflags_init("io_alloc_cbm",
+ RFTYPE_CTRL_INFO | RFTYPE_RES_CACHE);
+ }
}
void resctrl_file_fflags_init(const char *config, unsigned long fflags)
--
2.34.1
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