Currently, configuring the io_alloc_cbm interface requires an explicit
domain ID for each cache domain. On systems with high core counts and
numerous cache clusters, this requirement becomes cumbersome for
automation and management tasks that aim to apply a uniform policy.
Introduce a wildcard domain ID selector "*" for the io_alloc_cbm
interface. This enables users to update the Capacity Bitmask (CBM)
across all cache domains in a single operation.
For example, a user can write "*=0" to the io_alloc_cbm file to
programme every domain with the same mask. The value supplied must,
however, remain within the valid range defined by the resource
(e.g., min_cbm_bits).
Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
---
Documentation/filesystems/resctrl.rst | 10 ++++++++++
fs/resctrl/ctrlmondata.c | 15 ++++++++++++---
2 files changed, 22 insertions(+), 3 deletions(-)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 8c8ce678148a..948219e58882 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -215,6 +215,16 @@ related to allocation:
# cat /sys/fs/resctrl/info/L3/io_alloc_cbm
0=00ff;1=000f
+ Set each CBM to a specified value.
+
+ An ID of "*" configures all domains with the provided CBM.
+
+ Example::
+
+ # echo "*=0" > /sys/fs/resctrl/info/L3/io_alloc_cbm
+ # cat /sys/fs/resctrl/info/L3/io_alloc_cbm
+ 0=0;1=0
+
When CDP is enabled "io_alloc_cbm" associated with the CDP_DATA and CDP_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
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index b96b661626c2..f47331a97337 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -873,21 +873,26 @@ static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
struct rdt_ctrl_domain *d;
char *dom = NULL, *id;
unsigned long dom_id;
+ bool update_all;
next:
if (!line || line[0] == '\0')
return 0;
+ update_all = false;
dom = strsep(&line, ";");
id = strsep(&dom, "=");
- if (!dom || kstrtoul(id, 10, &dom_id)) {
+
+ if (dom && !strcmp(id, "*")) {
+ update_all = true;
+ } else if (!dom || kstrtoul(id, 10, &dom_id)) {
rdt_last_cmd_puts("Missing '=' or non-numeric domain\n");
return -EINVAL;
}
dom = strim(dom);
list_for_each_entry(d, &r->ctrl_domains, hdr.list) {
- if (d->hdr.id == dom_id) {
+ if (update_all || d->hdr.id == dom_id) {
data.buf = dom;
data.mode = RDT_MODE_SHAREABLE;
data.closid = closid;
@@ -903,10 +908,14 @@ static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
&d->staged_config[s->conf_type],
sizeof(d->staged_config[0]));
}
- goto next;
+ if (!update_all)
+ goto next;
}
}
+ if (update_all)
+ goto next;
+
rdt_last_cmd_printf("Invalid domain %lu\n", dom_id);
return -EINVAL;
}
--
2.51.0Hi Aaron,
On 2/10/26 1:07 PM, Aaron Tomlin wrote:
> Currently, configuring the io_alloc_cbm interface requires an explicit
(nit: "Currently" can be dropped. Expectation is that the patch starts
with context that is by default the current behavior.)
> domain ID for each cache domain. On systems with high core counts and
> numerous cache clusters, this requirement becomes cumbersome for
> automation and management tasks that aim to apply a uniform policy.
>
> Introduce a wildcard domain ID selector "*" for the io_alloc_cbm
> interface. This enables users to update the Capacity Bitmask (CBM)
"update the" -> "set the same"?
> across all cache domains in a single operation.
>
> For example, a user can write "*=0" to the io_alloc_cbm file to
This example seems redundant. The description is clear and the documentation
addition found in the patch describes this scenario anyway.
> programme every domain with the same mask. The value supplied must,
"programme" -> "program"
I suggest to drop the last sentence "The value supplied ..." since it
implies that the addition cannot do its own error checking.
> however, remain within the valid range defined by the resource
> (e.g., min_cbm_bits).
>
> Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
> ---
> Documentation/filesystems/resctrl.rst | 10 ++++++++++
> fs/resctrl/ctrlmondata.c | 15 ++++++++++++---
> 2 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index 8c8ce678148a..948219e58882 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -215,6 +215,16 @@ related to allocation:
> # cat /sys/fs/resctrl/info/L3/io_alloc_cbm
> 0=00ff;1=000f
>
> + Set each CBM to a specified value.
Above sentence seems redundant when compared to below sentence that is
more specific. Can it just be dropped?
> +
> + An ID of "*" configures all domains with the provided CBM.
> +
> + Example::
Just to make this clear I suggest to add caveat:
"Example on a system that does not require a minimum number of consecutive bits in the mask::"
> +
> + # echo "*=0" > /sys/fs/resctrl/info/L3/io_alloc_cbm
> + # cat /sys/fs/resctrl/info/L3/io_alloc_cbm
> + 0=0;1=0
> +
> When CDP is enabled "io_alloc_cbm" associated with the CDP_DATA and CDP_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
> diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
> index b96b661626c2..f47331a97337 100644
> --- a/fs/resctrl/ctrlmondata.c
> +++ b/fs/resctrl/ctrlmondata.c
> @@ -873,21 +873,26 @@ static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
> struct rdt_ctrl_domain *d;
> char *dom = NULL, *id;
> unsigned long dom_id;
> + bool update_all;
>
> next:
> if (!line || line[0] == '\0')
> return 0;
>
> + update_all = false;
> dom = strsep(&line, ";");
> id = strsep(&dom, "=");
> - if (!dom || kstrtoul(id, 10, &dom_id)) {
> +
> + if (dom && !strcmp(id, "*")) {
> + update_all = true;
> + } else if (!dom || kstrtoul(id, 10, &dom_id)) {
> rdt_last_cmd_puts("Missing '=' or non-numeric domain\n");
> return -EINVAL;
> }
>
> dom = strim(dom);
> list_for_each_entry(d, &r->ctrl_domains, hdr.list) {
> - if (d->hdr.id == dom_id) {
> + if (update_all || d->hdr.id == dom_id) {
While this code is correct in that dom_id will not be accessed when
update_all is true it makes the code more difficult to understand
when an uninitialized variable depends on certain flows.
> data.buf = dom;
> data.mode = RDT_MODE_SHAREABLE;
> data.closid = closid;
> @@ -903,10 +908,14 @@ static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
> &d->staged_config[s->conf_type],
> sizeof(d->staged_config[0]));
> }
> - goto next;
> + if (!update_all)
> + goto next;
> }
> }
>
> + if (update_all)
> + goto next;
One comment from v4 appears to be unaddressed. Copied here for convenience:
I see that this aims to support input like "*=f;*=0" but I do not see how something like
this can ever succeed since parse_cbm() stages the config and should fail if any domain
already has a config. Should this perhaps just return success here? This could be
made more robust by only returning success if there is no more text to parse, thus failing
on input like "*=f;1=f".
Below is a sample fixup that addresses the comments. What do you think?
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index 869e37f7d22a..9a7dfc48cb2e 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -954,17 +954,21 @@ static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
struct resctrl_schema *s, u32 closid)
{
enum resctrl_conf_type peer_type;
+ unsigned long dom_id = ULONG_MAX;
struct rdt_parse_data data;
struct rdt_ctrl_domain *d;
+ bool update_all = false;
char *dom = NULL, *id;
- unsigned long dom_id;
- bool update_all;
next:
if (!line || line[0] == '\0')
return 0;
- update_all = false;
+ if (update_all) {
+ rdt_last_cmd_puts("Configurations after global '*'\n");
+ return -EINVAL;
+ }
+
dom = strsep(&line, ";");
id = strsep(&dom, "=");
> +
> rdt_last_cmd_printf("Invalid domain %lu\n", dom_id);
> return -EINVAL;
> }
Reinette
On Wed, Feb 18, 2026 at 10:30:57AM -0800, Reinette Chatre wrote:
> Hi Aaron,
Hi Reinette,
> On 2/10/26 1:07 PM, Aaron Tomlin wrote:
> > Currently, configuring the io_alloc_cbm interface requires an explicit
>
> (nit: "Currently" can be dropped. Expectation is that the patch starts
> with context that is by default the current behavior.)
Acknowledged. I have dropped "Currently," from the opening sentence of the
commit message.
>
> > domain ID for each cache domain. On systems with high core counts and
> > numerous cache clusters, this requirement becomes cumbersome for
> > automation and management tasks that aim to apply a uniform policy.
> >
> > Introduce a wildcard domain ID selector "*" for the io_alloc_cbm
> > interface. This enables users to update the Capacity Bitmask (CBM)
>
> "update the" -> "set the same"?
Acknowledged. I have updated the phrasing to "set the same Capacity Bitmask
(CBM)" in the commit message.
> > across all cache domains in a single operation.
> >
> > For example, a user can write "*=0" to the io_alloc_cbm file to
>
> This example seems redundant. The description is clear and the documentation
> addition found in the patch describes this scenario anyway.
>
> > programme every domain with the same mask. The value supplied must,
>
> "programme" -> "program"
>
Acknowledged. I completely dropped the final paragraph containing the
redundant example, the typo, and the validation disclaimer from the commit
message.
> > however, remain within the valid range defined by the resource
> > (e.g., min_cbm_bits).
> >
> > Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
> > ---
> > Documentation/filesystems/resctrl.rst | 10 ++++++++++
> > fs/resctrl/ctrlmondata.c | 15 ++++++++++++---
> > 2 files changed, 22 insertions(+), 3 deletions(-)
> >
> > diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> > index 8c8ce678148a..948219e58882 100644
> > --- a/Documentation/filesystems/resctrl.rst
> > +++ b/Documentation/filesystems/resctrl.rst
> > @@ -215,6 +215,16 @@ related to allocation:
> > # cat /sys/fs/resctrl/info/L3/io_alloc_cbm
> > 0=00ff;1=000f
> >
> > + Set each CBM to a specified value.
>
> Above sentence seems redundant when compared to below sentence that is
> more specific. Can it just be dropped?
Yes. I removed "Set each CBM to a specified value" from resctrl.rst.
> > +
> > + An ID of "*" configures all domains with the provided CBM.
> > +
> > + Example::
>
> Just to make this clear I suggest to add caveat:
> "Example on a system that does not require a minimum number of consecutive bits in the mask::"
>
I updated the caveat preceding the example block in resctrl.rst exactly as
suggested.
> > +
> > + # echo "*=0" > /sys/fs/resctrl/info/L3/io_alloc_cbm
> > + # cat /sys/fs/resctrl/info/L3/io_alloc_cbm
> > + 0=0;1=0
> > +
> > When CDP is enabled "io_alloc_cbm" associated with the CDP_DATA and CDP_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
> > diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
> > index b96b661626c2..f47331a97337 100644
> > --- a/fs/resctrl/ctrlmondata.c
> > +++ b/fs/resctrl/ctrlmondata.c
> > @@ -873,21 +873,26 @@ static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
> > struct rdt_ctrl_domain *d;
> > char *dom = NULL, *id;
> > unsigned long dom_id;
> > + bool update_all;
> >
> > next:
> > if (!line || line[0] == '\0')
> > return 0;
> >
> > + update_all = false;
> > dom = strsep(&line, ";");
> > id = strsep(&dom, "=");
> > - if (!dom || kstrtoul(id, 10, &dom_id)) {
> > +
> > + if (dom && !strcmp(id, "*")) {
> > + update_all = true;
> > + } else if (!dom || kstrtoul(id, 10, &dom_id)) {
> > rdt_last_cmd_puts("Missing '=' or non-numeric domain\n");
> > return -EINVAL;
> > }
> >
> > dom = strim(dom);
> > list_for_each_entry(d, &r->ctrl_domains, hdr.list) {
> > - if (d->hdr.id == dom_id) {
> > + if (update_all || d->hdr.id == dom_id) {
>
> While this code is correct in that dom_id will not be accessed when
> update_all is true it makes the code more difficult to understand
> when an uninitialized variable depends on certain flows.
I applied your suggested change; at declaration to eliminate the
uninitialised variable state.
> > data.buf = dom;
> > data.mode = RDT_MODE_SHAREABLE;
> > data.closid = closid;
> > @@ -903,10 +908,14 @@ static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
> > &d->staged_config[s->conf_type],
> > sizeof(d->staged_config[0]));
> > }
> > - goto next;
> > + if (!update_all)
> > + goto next;
> > }
> > }
> >
> > + if (update_all)
> > + goto next;
>
> One comment from v4 appears to be unaddressed. Copied here for convenience:
> I see that this aims to support input like "*=f;*=0" but I do not see how something like
> this can ever succeed since parse_cbm() stages the config and should fail if any domain
> already has a config. Should this perhaps just return success here? This could be
> made more robust by only returning success if there is no more text to parse, thus failing
> on input like "*=f;1=f".
>
> Below is a sample fixup that addresses the comments. What do you think?
>
> diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
> index 869e37f7d22a..9a7dfc48cb2e 100644
> --- a/fs/resctrl/ctrlmondata.c
> +++ b/fs/resctrl/ctrlmondata.c
> @@ -954,17 +954,21 @@ static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
> struct resctrl_schema *s, u32 closid)
> {
> enum resctrl_conf_type peer_type;
> + unsigned long dom_id = ULONG_MAX;
> struct rdt_parse_data data;
> struct rdt_ctrl_domain *d;
> + bool update_all = false;
> char *dom = NULL, *id;
> - unsigned long dom_id;
> - bool update_all;
>
> next:
> if (!line || line[0] == '\0')
> return 0;
>
> - update_all = false;
> + if (update_all) {
> + rdt_last_cmd_puts("Configurations after global '*'\n");
> + return -EINVAL;
> + }
> +
> dom = strsep(&line, ";");
> id = strsep(&dom, "=");
>
>
> > +
> > rdt_last_cmd_printf("Invalid domain %lu\n", dom_id);
> > return -EINVAL;
> > }
>
I have applied it exactly as suggested.
Kind regards,
--
Aaron Tomlin
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