"io_alloc" feature in resctrl allows direct insertion of data from I/O
devices into the cache.
Introduce the 'io_alloc' resctrl file to indicate the support for the
feature.
Signed-off-by: Babu Moger <babu.moger@amd.com>
---
v9: Minor user doc(resctrl.rst) update.
v8: Updated Documentation/filesystems/resctrl.rst.
Moved resctrl_io_alloc_show() to fs/resctrl/ctrlmondata.c.
Added prototype for rdt_kn_parent_priv() in fs/resctrl/internal.h
so, it can be uses in other fs/resctrl/ files.
Added comment for io_alloc_init().
v7: Updated the changelog.
Updated user doc for io_alloc in resctrl.rst.
Added mutex rdtgroup_mutex in resctrl_io_alloc_show();
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 | 30 +++++++++++++++++++++++++++
fs/resctrl/ctrlmondata.c | 21 +++++++++++++++++++
fs/resctrl/internal.h | 5 +++++
fs/resctrl/rdtgroup.c | 24 ++++++++++++++++++++-
4 files changed, 79 insertions(+), 1 deletion(-)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 4866a8a4189f..89aab17b00cb 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -136,6 +136,36 @@ related to allocation:
"1":
Non-contiguous 1s value in CBM is supported.
+"io_alloc":
+ "io_alloc" enables system software to configure the portion of
+ the cache allocated for I/O traffic. File may only exist if the
+ system supports this feature on some of its cache resources.
+
+ "disabled":
+ Resource supports "io_alloc" but the feature is disabled.
+ Portions of cache used for allocation of I/O traffic cannot
+ be configured.
+ "enabled":
+ Portions of cache used for allocation of I/O traffic
+ can be configured using "io_alloc_cbm".
+ "not supported":
+ Support not available for this resource.
+
+ The underlying implementation may reduce resources available to
+ general (CPU) cache allocation. See architecture specific notes
+ below. Depending on usage requirements the feature can be enabled
+ or disabled.
+
+ On AMD systems, io_alloc feature is supported by the L3 Smart
+ Data Cache Injection Allocation Enforcement (SDCIAE). The CLOSID for
+ io_alloc is the highest CLOSID supported by the resource. When
+ io_alloc is enabled, the highest CLOSID is dedicated to io_alloc and
+ no longer available for general (CPU) cache allocation. When CDP is
+ enabled, io_alloc routes I/O traffic using the highest CLOSID allocated
+ for the instruction cache (L3CODE), making this CLOSID no longer
+ available for general (CPU) cache allocation for both the L3CODE and
+ L3DATA resources.
+
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 d98e0d2de09f..d495a5d5c9d5 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -664,3 +664,24 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
rdtgroup_kn_unlock(of->kn);
return ret;
}
+
+int resctrl_io_alloc_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;
+
+ mutex_lock(&rdtgroup_mutex);
+
+ if (r->cache.io_alloc_capable) {
+ if (resctrl_arch_get_io_alloc_enabled(r))
+ seq_puts(seq, "enabled\n");
+ else
+ seq_puts(seq, "disabled\n");
+ } else {
+ seq_puts(seq, "not supported\n");
+ }
+
+ mutex_unlock(&rdtgroup_mutex);
+
+ return 0;
+}
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index 0a1eedba2b03..1a4543c2b988 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -375,6 +375,11 @@ bool closid_allocated(unsigned int closid);
int resctrl_find_cleanest_closid(void);
+int resctrl_io_alloc_show(struct kernfs_open_file *of, struct seq_file *seq,
+ void *v);
+
+void *rdt_kn_parent_priv(struct kernfs_node *kn);
+
#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 5f0b7cfa1cc2..41ce2be4b2cb 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -981,7 +981,7 @@ static int rdt_last_cmd_status_show(struct kernfs_open_file *of,
return 0;
}
-static void *rdt_kn_parent_priv(struct kernfs_node *kn)
+void *rdt_kn_parent_priv(struct kernfs_node *kn)
{
/*
* The parent pointer is only valid within RCU section since it can be
@@ -1893,6 +1893,12 @@ static struct rftype res_common_files[] = {
.kf_ops = &rdtgroup_kf_single_ops,
.seq_show = rdt_thread_throttle_mode_show,
},
+ {
+ .name = "io_alloc",
+ .mode = 0444,
+ .kf_ops = &rdtgroup_kf_single_ops,
+ .seq_show = resctrl_io_alloc_show,
+ },
{
.name = "max_threshold_occupancy",
.mode = 0644,
@@ -2062,6 +2068,20 @@ static void thread_throttle_mode_init(void)
RFTYPE_CTRL_INFO | RFTYPE_RES_MB);
}
+/*
+ * The resctrl file "io_alloc" is added using L3 resource. However, it results
+ * in this file being visible for *all* cache resources (eg. L2 cache),
+ * whether it supports "io_alloc" or not.
+ */
+static void io_alloc_init(void)
+{
+ struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
+
+ if (r->cache.io_alloc_capable)
+ resctrl_file_fflags_init("io_alloc", RFTYPE_CTRL_INFO |
+ RFTYPE_RES_CACHE);
+}
+
void resctrl_file_fflags_init(const char *config, unsigned long fflags)
{
struct rftype *rft;
@@ -4246,6 +4266,8 @@ int resctrl_init(void)
thread_throttle_mode_init();
+ io_alloc_init();
+
ret = resctrl_mon_resource_init();
if (ret)
return ret;
--
2.34.1Hi Babu,
On 9/2/25 3:41 PM, Babu Moger wrote:
> "io_alloc" feature in resctrl allows direct insertion of data from I/O
> devices into the cache.
>
> Introduce the 'io_alloc' resctrl file to indicate the support for the
> feature.
Changelog that aims to address feeback received in ABMC series (avoid repetition
and document any non-obvious things), please feel free to improve:
Introduce the "io_alloc" resctrl file to the "info" area of a cache
resource, for example /sys/fs/resctrl/info/L3/io_alloc. "io_alloc"
indicates support for the "io_alloc" feature that allows direct
insertion of data from I/O devices into the cache.
Restrict exposing support for "io_alloc" to the L3 resource that is the
only resource where this feature can be backed by AMD's L3 Smart Data Cache
Injection Allocation Enforcement (SDCIAE). With that, the "io_alloc" file is only
visible to user space if the L3 resource supports "io_alloc". Doing
so makes the file visible for all cache resources though, for example also L2
cache (if it supports cache allocation). As a consequence, add capability for
file to report expected "enabled" and "disabled", as well as "not supported".
>
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
...
> ---
> Documentation/filesystems/resctrl.rst | 30 +++++++++++++++++++++++++++
> fs/resctrl/ctrlmondata.c | 21 +++++++++++++++++++
> fs/resctrl/internal.h | 5 +++++
> fs/resctrl/rdtgroup.c | 24 ++++++++++++++++++++-
> 4 files changed, 79 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index 4866a8a4189f..89aab17b00cb 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -136,6 +136,36 @@ related to allocation:
> "1":
> Non-contiguous 1s value in CBM is supported.
>
> +"io_alloc":
> + "io_alloc" enables system software to configure the portion of
> + the cache allocated for I/O traffic. File may only exist if the
> + system supports this feature on some of its cache resources.
> +
> + "disabled":
> + Resource supports "io_alloc" but the feature is disabled.
> + Portions of cache used for allocation of I/O traffic cannot
> + be configured.
> + "enabled":
> + Portions of cache used for allocation of I/O traffic
> + can be configured using "io_alloc_cbm".
> + "not supported":
> + Support not available for this resource.
> +
After trying to rework the changelogs I believe the portion of doc below is better suited for
the next patch that adds support for enable/disable where CLOSIDs are relevant.
> + The underlying implementation may reduce resources available to
> + general (CPU) cache allocation. See architecture specific notes
> + below. Depending on usage requirements the feature can be enabled
> + or disabled.
> +
> + On AMD systems, io_alloc feature is supported by the L3 Smart
> + Data Cache Injection Allocation Enforcement (SDCIAE). The CLOSID for
> + io_alloc is the highest CLOSID supported by the resource. When
> + io_alloc is enabled, the highest CLOSID is dedicated to io_alloc and
> + no longer available for general (CPU) cache allocation. When CDP is
> + enabled, io_alloc routes I/O traffic using the highest CLOSID allocated
> + for the instruction cache (L3CODE), making this CLOSID no longer
> + available for general (CPU) cache allocation for both the L3CODE and
> + L3DATA resources.
> +
> Memory bandwidth(MB) subdirectory contains the following files
> with respect to allocation:
>
Reinette
Hi Reinette, On 9/18/2025 12:28 AM, Reinette Chatre wrote: > Hi Babu, > > On 9/2/25 3:41 PM, Babu Moger wrote: >> "io_alloc" feature in resctrl allows direct insertion of data from I/O >> devices into the cache. >> >> Introduce the 'io_alloc' resctrl file to indicate the support for the >> feature. > > Changelog that aims to address feeback received in ABMC series (avoid repetition > and document any non-obvious things), please feel free to improve: > > Introduce the "io_alloc" resctrl file to the "info" area of a cache > resource, for example /sys/fs/resctrl/info/L3/io_alloc. "io_alloc" > indicates support for the "io_alloc" feature that allows direct > insertion of data from I/O devices into the cache. > > Restrict exposing support for "io_alloc" to the L3 resource that is the > only resource where this feature can be backed by AMD's L3 Smart Data Cache > Injection Allocation Enforcement (SDCIAE). With that, the "io_alloc" file is only > visible to user space if the L3 resource supports "io_alloc". Doing > so makes the file visible for all cache resources though, for example also L2 > cache (if it supports cache allocation). As a consequence, add capability for > file to report expected "enabled" and "disabled", as well as "not supported". > > Looks good. Thanks >> >> Signed-off-by: Babu Moger <babu.moger@amd.com> >> --- > > ... > >> --- >> Documentation/filesystems/resctrl.rst | 30 +++++++++++++++++++++++++++ >> fs/resctrl/ctrlmondata.c | 21 +++++++++++++++++++ >> fs/resctrl/internal.h | 5 +++++ >> fs/resctrl/rdtgroup.c | 24 ++++++++++++++++++++- >> 4 files changed, 79 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst >> index 4866a8a4189f..89aab17b00cb 100644 >> --- a/Documentation/filesystems/resctrl.rst >> +++ b/Documentation/filesystems/resctrl.rst >> @@ -136,6 +136,36 @@ related to allocation: >> "1": >> Non-contiguous 1s value in CBM is supported. >> >> +"io_alloc": >> + "io_alloc" enables system software to configure the portion of >> + the cache allocated for I/O traffic. File may only exist if the >> + system supports this feature on some of its cache resources. >> + >> + "disabled": >> + Resource supports "io_alloc" but the feature is disabled. >> + Portions of cache used for allocation of I/O traffic cannot >> + be configured. >> + "enabled": >> + Portions of cache used for allocation of I/O traffic >> + can be configured using "io_alloc_cbm". >> + "not supported": >> + Support not available for this resource. >> + > > After trying to rework the changelogs I believe the portion of doc below is better suited for > the next patch that adds support for enable/disable where CLOSIDs are relevant. Sure. Thanks Babu > >> + The underlying implementation may reduce resources available to >> + general (CPU) cache allocation. See architecture specific notes >> + below. Depending on usage requirements the feature can be enabled >> + or disabled. >> + >> + On AMD systems, io_alloc feature is supported by the L3 Smart >> + Data Cache Injection Allocation Enforcement (SDCIAE). The CLOSID for >> + io_alloc is the highest CLOSID supported by the resource. When >> + io_alloc is enabled, the highest CLOSID is dedicated to io_alloc and >> + no longer available for general (CPU) cache allocation. When CDP is >> + enabled, io_alloc routes I/O traffic using the highest CLOSID allocated >> + for the instruction cache (L3CODE), making this CLOSID no longer >> + available for general (CPU) cache allocation for both the L3CODE and >> + L3DATA resources. >> + >> Memory bandwidth(MB) subdirectory contains the following files >> with respect to allocation: >> > > Reinette > >
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