Re: [RFC] mpam,x86,fs/resctrl: Generic schema description Proof of Concept

[Chen, Yu C]

Hi Reinette,

On 6/5/2026 5:42 AM, Reinette Chatre wrote:
> Hi Tony,
>
> On 6/3/26 11:46 AM, Luck, Tony wrote:
> > Reinette,
> >
> > Tiny bug in "mpam,x86,fs/resctrl: Transition resource control to a list"
> >
> > > /*
> > >   * Return length needed to display longest control suffix.
> > >   * Add 1 for the "_" character when control name exists.
> > >   */
> > > size_t resctrl_resource_ctrl_max_len(struct rdt_resource *r)
> > > {
> > > 	struct resctrl_ctrl *ctrl;
> > > 	size_t total = 0;
> > > 	size_t len;
> > >
> > > 	for_each_resource_ctrl(ctrl,r) {
> > > 		len = strlen(resctrl_ctrl_name_str(ctrl->name));
> > > 		if (len)
> > > 			total += 1 + len;
> >
> > Should be:
> >
> > 			total = max(total, 1 + len);
>
> Thank you very much. I squashed this locally.

A minor alignment schemata issue is found when testing region-aware RDT:
[resctrl]# cat schemata
            MB:0=100
            MB_REGION0_OPT:0=255
            MB_REGION0_MIN:0=255
            MB_REGION0_MAX:0=255
            MB_REGION1_OPT:0=255
            MB_REGION1_MIN:0=255
            MB_REGION1_MAX:0=255
            L2:0=ffff;2=ffff;4=ffff
            L3:0=3ff

The schemata file right-justified only the resource name in a
max_name_width field, then printed the control suffix afterwards
without padding. Since max_name_width reserves space for name plus
suffix, this left a run of spaces before every line. A small hacky
fix:

diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index 9b51464b66b7..7d517f3457bf 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -521,6 +521,7 @@ ssize_t rdtgroup_schemata_write(struct 
kernfs_open_file *of,
 static void show_doms(struct seq_file *s, struct rdt_resource_final *f,
                      bool print_ctrl, int closid, struct resctrl_ctrl 
*ctrl)
 {
+       char name[20];
        struct rdt_resource *r = f->res;
        struct rdt_ctrl_domain *dom;
        bool sep = false;
@@ -529,11 +530,13 @@ static void show_doms(struct seq_file *s, struct 
rdt_resource_final *f,
        /* Walking r->domains, ensure it can't race with cpuhp */
        lockdep_assert_cpus_held();

-       if (print_ctrl)
-               seq_printf(s, "%*s%s%s:", max_name_width, f->name,
-                               resctrl_ctrl_is_default(ctrl) ? "" : "_",
-                               resctrl_ctrl_is_default(ctrl) ?
-                                "" : resctrl_ctrl_name_str(ctrl->name));
+       if (print_ctrl) {
+               snprintf(name, sizeof(name), "%s%s%s", f->name,
+                        resctrl_ctrl_is_default(ctrl) ? "" : "_",
+                        resctrl_ctrl_is_default(ctrl) ?
+                         "" : resctrl_ctrl_name_str(ctrl->name));
+               seq_printf(s, "%*s:", max_name_width, name);
+       }
        list_for_each_entry(dom, &ctrl->domains, hdr.list) {
                if (sep)
                        seq_puts(s, ";");
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index c1aac0dcd332..916bf6a8eab4 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1654,6 +1654,7 @@ static int rdtgroup_size_show(struct 
kernfs_open_file *of,
        struct rdtgroup *rdtgrp;
        struct rdt_resource *r;
        unsigned int size;
+       char name[20];
        u32 ctrl_val;
        int ret = 0;
        u32 closid;
@@ -1693,11 +1694,11 @@ static int rdtgroup_size_show(struct 
kernfs_open_file *of,
                type = f->conf_type;
                for_each_resource_ctrl(ctrl, r) {
                        sep = false;
-                       seq_printf(s, "%*s", max_name_width, f->name);
-                       if (!resctrl_ctrl_is_default(ctrl))
-                               seq_printf(s, "_%s:", 
resctrl_ctrl_name_str(ctrl->name));
-                       else
-                               seq_putc(s, ':');
+                       snprintf(name, sizeof(name), "%s%s%s", f->name,
+                                resctrl_ctrl_is_default(ctrl) ? "" : "_",
+                                resctrl_ctrl_is_default(ctrl) ?
+                                 "" : resctrl_ctrl_name_str(ctrl->name));
+                       seq_printf(s, "%*s:", max_name_width, name);
                        list_for_each_entry(d, &ctrl->domains, hdr.list) {
                                if (sep)
                                        seq_putc(s, ';');



And it becomes:
[ resctrl]# cat schemata
            MB:0=100
MB_REGION0_OPT:0=255
MB_REGION0_MIN:0=255
MB_REGION0_MAX:0=255
MB_REGION1_OPT:0=255
MB_REGION1_MIN:0=255
MB_REGION1_MAX:0=255
            L2:0=ffff;2=ffff;4=ffff
            L3:0=3ff

thanks,
Chenyu