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Message-ID: <a5bc5ecf27c229a0cf429dba6a174e39cf83357b.1754436586.git.babu.moger@amd.com>
Date: Tue, 5 Aug 2025 18:30:27 -0500
From: Babu Moger <babu.moger@....com>
To: <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>, <Neeraj.Upadhyay@....com>,
<david@...hat.com>, <arnd@...db.de>, <fvdl@...gle.com>, <seanjc@...gle.com>,
<thomas.lendacky@....com>, <pawan.kumar.gupta@...ux.intel.com>,
<babu.moger@....com>, <yosry.ahmed@...ux.dev>, <sohil.mehta@...el.com>,
<xin@...or.com>, <kai.huang@...el.com>, <xiaoyao.li@...el.com>,
<peterz@...radead.org>, <me@...aill.net>, <mario.limonciello@....com>,
<xin3.li@...el.com>, <ebiggers@...gle.com>, <ak@...ux.intel.com>,
<chang.seok.bae@...el.com>, <andrew.cooper3@...rix.com>,
<perry.yuan@....com>, <linux-doc@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <manali.shukla@....com>,
<gautham.shenoy@....com>
Subject: [PATCH v8 07/10] fs/resctrl: Introduce interface to display io_alloc CBMs
The io_alloc feature in resctrl enables system software to configure
the portion of the cache allocated for I/O traffic.
Add "io_alloc_cbm" resctrl file to display CBMs (Capacity Bit Mask) of
io_alloc feature.
The CBM interface file io_alloc_cbm resides 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 the L3CODE resource. To ensure consistent cache allocation
behavior, the L3CODE and L3DATA resources must remain synchronized.
rdtgroup_init_cat() function takes both L3CODE and L3DATA into account when
initializing CBMs for new groups. The io_alloc feature adheres to this
same principle, meaning that the Cache Bit Masks (CBMs) accessed through
either L3CODE or L3DATA will reflect identical values.
Signed-off-by: Babu Moger <babu.moger@....com>
---
v8: Updated the changelog.
Moved resctrl_io_alloc_cbm_show() to fs/resctrl/ctrlmondata.c.
show_doms is remains static with this change.
v7: Updated changelog.
Updated use doc (resctrl.rst).
Removed if (io_alloc_closid < 0) check. Not required anymore.
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 | 19 +++++++++++++
fs/resctrl/ctrlmondata.c | 39 ++++++++++++++++++++++++---
fs/resctrl/internal.h | 3 +++
fs/resctrl/rdtgroup.c | 11 +++++++-
4 files changed, 68 insertions(+), 4 deletions(-)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index bd0a633afbb9..3002f7fdb2fe 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -173,6 +173,25 @@ related to allocation:
available for general (CPU) cache allocation for both the L3CODE and
L3DATA resources.
+"io_alloc_cbm":
+ CBMs(Capacity Bit Masks) that describe the portions of cache instances
+ to which I/O traffic from supported I/O devices are routed when "io_alloc"
+ is enabled.
+
+ 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
+
+ When CDP is enabled "io_alloc_cbm" associated with the DATA and CODE
+ resources may reflect the same values. For example, values read from and
+ written to /sys/fs/resctrl/info/L3DATA/io_alloc_cbm may be reflected by
+ /sys/fs/resctrl/info/L3CODE/io_alloc_cbm and vice versa.
+
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 bf982eab7b18..edb9dd131eed 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)
+static 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 {
@@ -822,3 +824,34 @@ ssize_t resctrl_io_alloc_write(struct kernfs_open_file *of, char *buf,
return ret ?: nbytes;
}
+
+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;
+ int ret = 0;
+
+ cpus_read_lock();
+ mutex_lock(&rdtgroup_mutex);
+
+ rdt_last_cmd_clear();
+
+ if (!r->cache.io_alloc_capable) {
+ rdt_last_cmd_printf("io_alloc is not supported on %s\n", s->name);
+ ret = -ENODEV;
+ goto out_unlock;
+ }
+
+ if (!resctrl_arch_get_io_alloc_enabled(r)) {
+ rdt_last_cmd_printf("io_alloc is not enabled on %s\n", s->name);
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ show_doms(seq, s, NULL, resctrl_io_alloc_closid(r));
+
+out_unlock:
+ mutex_unlock(&rdtgroup_mutex);
+ cpus_read_unlock();
+ return ret;
+}
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index 335def7af1f6..49934cd3dc40 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -389,6 +389,9 @@ enum resctrl_conf_type resctrl_peer_type(enum resctrl_conf_type my_type);
ssize_t resctrl_io_alloc_write(struct kernfs_open_file *of, char *buf,
size_t nbytes, loff_t off);
+int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, struct seq_file *seq,
+ void *v);
+
const char *rdtgroup_name_by_closid(int closid);
#ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 380ebc86c748..6af8ff6c8385 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1917,6 +1917,12 @@ 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 = "max_threshold_occupancy",
.mode = 0644,
@@ -2095,9 +2101,12 @@ 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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