"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>
---
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 | 25 +++++++++++++++++
fs/resctrl/rdtgroup.c | 39 +++++++++++++++++++++++++++
2 files changed, 64 insertions(+)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index c3c412733632..354e6a00fa45 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -143,6 +143,31 @@ 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":
+ 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 on the system.
+
+ 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, the io_alloc feature is supported by the L3 Smart
+ Data Cache Injection Allocation Enforcement (SDCIAE). The CLOSID for
+ io_alloc is determined by the highest CLOSID supported by the resource.
+ When CDP is enabled, io_alloc routes I/O traffic using the highest
+ CLOSID allocated for the instruction cache (L3CODE).
+
Memory bandwidth(MB) subdirectory contains the following files
with respect to allocation:
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index a2eea85aecc8..d7c4417b4516 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1836,6 +1836,28 @@ static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
return ret ?: nbytes;
}
+static 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;
+}
+
/* rdtgroup information files for one cache resource. */
static struct rftype res_common_files[] = {
{
@@ -1926,6 +1948,12 @@ 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,
@@ -2095,6 +2123,15 @@ static void thread_throttle_mode_init(void)
RFTYPE_CTRL_INFO | RFTYPE_RES_MB);
}
+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;
@@ -4282,6 +4319,8 @@ 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 7/10/25 10:16 AM, 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.
>
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
...
> ---
> Documentation/filesystems/resctrl.rst | 25 +++++++++++++++++
> fs/resctrl/rdtgroup.c | 39 +++++++++++++++++++++++++++
> 2 files changed, 64 insertions(+)
>
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index c3c412733632..354e6a00fa45 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -143,6 +143,31 @@ 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":
> + 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 on the system.
"Support not available on the system." -> "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:
"disabled:" -> "disabled."?
> +
> + On AMD systems, the io_alloc feature is supported by the L3 Smart
> + Data Cache Injection Allocation Enforcement (SDCIAE). The CLOSID for
> + io_alloc is determined by the highest CLOSID supported by the resource.
"is determined by the" -> "is the"?
To make clear connection with previous paragraph you can append something like:
When io_alloc is enabled on an AMD system 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).
To clear up what happens with L3DATA, what do you think of appending something like:
, 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/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index a2eea85aecc8..d7c4417b4516 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -1836,6 +1836,28 @@ static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
> return ret ?: nbytes;
> }
>
> +static int resctrl_io_alloc_show(struct kernfs_open_file *of,
Please move to ctrlmondata.c
> + 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;
> +}
> +
> /* rdtgroup information files for one cache resource. */
> static struct rftype res_common_files[] = {
> {
> @@ -1926,6 +1948,12 @@ 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,
> @@ -2095,6 +2123,15 @@ static void thread_throttle_mode_init(void)
> RFTYPE_CTRL_INFO | RFTYPE_RES_MB);
> }
>
> +static void io_alloc_init(void)
This function's comment can benefit from a snippet that highlights that
even though this operates on hardcoded L3 resource it results in this file
being visible for *all* cache resources (eg. L2 cache also), whether they
support io_alloc or not.
> +{
> + 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;
> @@ -4282,6 +4319,8 @@ int resctrl_init(void)
>
> thread_throttle_mode_init();
>
> + io_alloc_init();
> +
> ret = resctrl_mon_resource_init();
> if (ret)
> return ret;
Reinette
Hi Reinette,
On 7/21/25 18:36, Reinette Chatre wrote:
> Hi Babu,
>
> On 7/10/25 10:16 AM, 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.
>>
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>> ---
>
> ...
>
>> ---
>> Documentation/filesystems/resctrl.rst | 25 +++++++++++++++++
>> fs/resctrl/rdtgroup.c | 39 +++++++++++++++++++++++++++
>> 2 files changed, 64 insertions(+)
>>
>> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
>> index c3c412733632..354e6a00fa45 100644
>> --- a/Documentation/filesystems/resctrl.rst
>> +++ b/Documentation/filesystems/resctrl.rst
>> @@ -143,6 +143,31 @@ 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":
>> + 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 on the system.
>
> "Support not available on the system." -> "Support not available for this resource."?
Sure.
>
>> +
>> + 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:
>
> "disabled:" -> "disabled."?
Sure.
>
>> +
>> + On AMD systems, the io_alloc feature is supported by the L3 Smart
>> + Data Cache Injection Allocation Enforcement (SDCIAE). The CLOSID for
>> + io_alloc is determined by the highest CLOSID supported by the resource.
>
> "is determined by the" -> "is the"?
>
Sure.
> To make clear connection with previous paragraph you can append something like:
> When io_alloc is enabled on an AMD system the highest CLOSID is dedicated to
> io_alloc and no longer available for general (CPU) cache allocation.
Sure.
>
>> + When CDP is enabled, io_alloc routes I/O traffic using the highest
>> + CLOSID allocated for the instruction cache (L3CODE).
>
> To clear up what happens with L3DATA, what do you think of appending something like:
> , making this CLOSID no longer available for general (CPU) cache
> allocation for both the L3CODE and L3DATA resources.
>
Sure.
>> +
>> Memory bandwidth(MB) subdirectory contains the following files
>> with respect to allocation:
>>
>> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
>> index a2eea85aecc8..d7c4417b4516 100644
>> --- a/fs/resctrl/rdtgroup.c
>> +++ b/fs/resctrl/rdtgroup.c
>> @@ -1836,6 +1836,28 @@ static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
>> return ret ?: nbytes;
>> }
>>
>> +static int resctrl_io_alloc_show(struct kernfs_open_file *of,
>
> Please move to ctrlmondata.c
Yes.
>
>
>> + 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;
>> +}
>> +
>> /* rdtgroup information files for one cache resource. */
>> static struct rftype res_common_files[] = {
>> {
>> @@ -1926,6 +1948,12 @@ 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,
>> @@ -2095,6 +2123,15 @@ static void thread_throttle_mode_init(void)
>> RFTYPE_CTRL_INFO | RFTYPE_RES_MB);
>> }
>>
>> +static void io_alloc_init(void)
>
> This function's comment can benefit from a snippet that highlights that
> even though this operates on hardcoded L3 resource it results in this file
> being visible for *all* cache resources (eg. L2 cache also), whether they
> support io_alloc or not.
Added the comment.
>
>> +{
>> + 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;
>> @@ -4282,6 +4319,8 @@ int resctrl_init(void)
>>
>> thread_throttle_mode_init();
>>
>> + io_alloc_init();
>> +
>> ret = resctrl_mon_resource_init();
>> if (ret)
>> return ret;
>
> Reinette
>
--
Thanks
Babu Moger
© 2016 - 2026 Red Hat, Inc.