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@xxxxxxx>
> ---
...
> ---
> 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
