resctrl_arch_cntr_read(9)

💅 resctrl_arch_cntr_read(9) 💅

okay bestie, welcome to the Kernel API Manual ✨ — yes this is one of those pages, a kernel function from ./include/linux, and honestly? she's a little niche but she serves 🎀

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🌸 NAME 🌸

resctrl_arch_cntr_read — read the event data that corresponds to the counter ID assigned to the RMID, event pair for this resource and domain 🫶

Like, you've got a counter ID, you've got an RMID + event pairing, and this is the girl that goes and fetches the actual numbers for that specific resource and domain. no cap 💖

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✨ SYNOPSIS ✨

int resctrl_arch_cntr_read (struct rdt_resource *r , struct
       rdt_l3_mon_domain *d , u32 closid , u32 rmid , int cntr_id , enum
       resctrl_event_id eventid , u64 *val );

seven whole parameters, she's that girl 🔥

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🦋 ARGUMENTS 🦋

• r — the resource you wanna read the counter from, periodt 💫
• d — the domain you wanna read the counter from 🎀
• closid — the CLOSID that matches the RMID, they're a matched set, iykyk 💅
• rmid — the RMID that cntr_id is assigned to 🫶
• cntr_id — literally just the counter you're reading bestie 🌸
• eventid — the MBM event that cntr_id is assigned to ⭐
• val — the result of the counter read, in bytes 🍓

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💜 DESCRIPTION 💜

so the vibe here is: this is called on a CPU that belongs to domain d, but only when "mbm_event" mode is enabled 👑

and then the way it gets called? it's called from a non-migrateable process context via smp_call_on_cpu — unless all CPUs are nohz_full, in which case (plot twist 😭) it's called via IPI, specifically smp_call_function_any. main character energy from the scheduler ngl 💀

no cap, that nohz_full caveat is real — the calling path genuinely changes depending on it, so don't come for me if you forgot 🙈

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🌈 RETURN 🌈

0 on success bestie 🥳 — or -EIO, -EINVAL etc. on error 😭 (yes, there are others, the manpage says "etc" and I'm not about to invent any, fr fr)

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🧚 SEE ALSO 🧚

• Kernel file ./include/linux/resctrl.h 👑
• 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 rdt_l3_mon_domain(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_reset_cntr(9)
• resctrl_arch_io_alloc_enable(9)
• resctrl_arch_get_io_alloc_enabled(9)

that's a whole friend group right there, go read all of them, be thorough, slay 💅✨

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💖 and that's the page!! 💖 sourced straight from ./include/linux, dated October 2026 — go off, kernel docs, you ate 🫶🎀🦋⭐