STRUCT RDT_L3_MON_DOMAIN(9)

💖 struct rdt_l3_mon_domain(9) 💖

okay so bestie, welcome to the Kernel API Manual ✨ — yes, that's the vibe, we're in the kernel docs today and honestly? it's giving main character energy. this page is all about struct rdt_l3_mon_domain, and no cap, it's kind of iconic once you get it.

---

🌸 NAME 🌸

struct rdt_l3_mon_domain — literally just a group of CPUs that share RDT_RESOURCE_L3 monitoring 🎀 that's it, that's the whole thing, and it's lowkey important, iykyk.

---

✨ SYNOPSIS ✨

here's the actual shape of it, copied exactly because we do not mess with the code, periodt:

struct rdt_l3_mon_domain {
    struct rdt_domain_hdr           hdr;
    unsigned int                    ci_id;
    unsigned long                   *rmid_busy_llc;
    struct mbm_state                *mbm_states[QOS_NUM_L3_MBM_EVENTS];
    struct delayed_work             mbm_over;
    struct delayed_work             cqm_limbo;
    int mbm_work_cpu;
    int cqm_work_cpu;
    struct mbm_cntr_cfg             *cntr_cfg;
 };

---

🦋 Members 🦋

okay bestie, member-by-member tour, let's go 💅

• hdr — the common header for different domain types. it's the shared little crown every domain type wears 👑
• ci_id — the cache info id for this domain. yes, this domain specifically 🎯
• rmid_busy_llc — bitmap of which limbo RMIDs are above threshold. a whole bitmap, bestie, tracking the limbo RMIDs that overshot 🔥
• mbm_states — per-event pointer to the MBM event's saved state. and here's the tea: an MBM event's state is an array of struct mbm_state indexed by RMID on x86, or by combined CLOSID, RMID on Arm. different architectures, different indexing, same slay 🌈
• mbm_over — the worker that periodically reads MBM h/w counters. it's on a schedule, it's diligent, it's that girl ⏰
• cqm_limbo — the worker that periodically reads CQM h/w counters. same energy, different counters 💫
• mbm_work_cpu — the worker CPU for MBM h/w counters. somebody's gotta do it 🫶
• cqm_work_cpu — the worker CPU for CQM h/w counters. and this someone too 💜
• cntr_cfg — array of assignable counters' configuration, indexed by counter ID. array, indexed, configured, done ✨

---

💀 SEE ALSO 💀

okay so this list is long and we are not skipping a single one, because every reference matters bestie 💖 the kernel file is ./include/linux/resctrl.h and the whole squad is:

• enum resctrl_conf_type(9)
• struct resctrl_staged_config(9)
• struct rdt_domain_hdr(9)
• struct rdt_ctrl_domain(9)
• struct mbm_cntr_cfg(9)
• struct resctrl_cache(9)
• enum membw_throttle_mode(9)
• struct resctrl_membw(9)
• enum resctrl_schema_fmt(9)
• struct resctrl_mon(9)
• struct rdt_resource(9)
• struct resctrl_schema(9)
• resctrl_arch_sync_cpu_closid_rmid(9)
• resctrl_get_default_ctrl(9)
• resctrl_arch_mon_event_config_write(9)
• resctrl_arch_mon_event_config_read(9)
• resctrl_arch_mbm_cntr_assign_enabled(9)
• resctrl_arch_mbm_cntr_assign_set(9)
• resctrl_arch_rmid_read(9)
• resctrl_arch_rmid_read_context_check(9)
• resctrl_find_domain(9)
• resctrl_arch_reset_rmid(9)
• resctrl_arch_reset_rmid_all(9)
• resctrl_arch_reset_all_ctrls(9)
• resctrl_arch_config_cntr(9)
• resctrl_arch_cntr_read(9)
• resctrl_arch_reset_cntr(9)
• resctrl_arch_io_alloc_enable(9)
• resctrl_arch_get_io_alloc_enabled(9)

like, a whole friend group fr fr 🫶

---

and that's the page!! mwah 💋 it lives over in ./include/linux and it's dated October 2026 — so go read it when the calendar catches up, bestie. bye bye, stan resctrl, drink water, and remember: the vibe changes, the facts do not 💅💖✨