Re: [PATCH v9 06/12] x86,fs/resctrl: Move resctrl_arch_round_mon_val() out of line

[Ben Horgan <ben.horgan@arm.com>]

Hi Chen,

On 14/10/2026 03:59, Chen Yu wrote:
> resctrl_arch_round_mon_val() is an inline function in the architecture
> header. It is only called during resctrl initialization and when user space
> writes "max_threshold_occupancy", neither of which is a hot path that
> benefits from inlining.
> 
> Upcoming ERDT support needs resctrl_arch_round_mon_val() to consult
> ERDT-specific state. Keeping it inline would force ERDT prototypes into the
> architecture header, fragmenting the ERDT code across files.
> 
> Move resctrl_arch_round_mon_val() into monitor.c and declare it in
> include/linux/resctrl.h alongside the other resctrl_arch_*() calls. Move the
> MPAM stub from arm_mpam.h into mpam_resctrl.c accordingly.

For the MPAM part:

Acked-by: Ben Horgan <ben.horgan@arm.com>

Thanks,

Ben


> 
> No functional change.
> 
> Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
> Signed-off-by: Chen Yu <yu.c.chen@intel.com>
> ---
> Changes since v8:
> - New patch. v8 added erdt_get_scale() and erdt_cpu_has() prototypes to
>   asm/resctrl.h only to keep resctrl_arch_round_mon_val() inline, which
>   fragmented the ERDT code. Move the function out of line instead so the
>   ERDT prototypes can stay in the resctrl internal header.
>   (Reinette Chatre)
> 
>  arch/x86/include/asm/resctrl.h        | 9 ---------
>  arch/x86/kernel/cpu/resctrl/monitor.c | 9 +++++++++
>  drivers/resctrl/mpam_resctrl.c        | 5 +++++
>  include/linux/arm_mpam.h              | 5 -----
>  include/linux/resctrl.h               | 1 +
>  5 files changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
> index 8f6edcdcfd87..738de74235bd 100644
> --- a/arch/x86/include/asm/resctrl.h
> +++ b/arch/x86/include/asm/resctrl.h
> @@ -130,15 +130,6 @@ static inline void __resctrl_sched_in(struct task_struct *tsk)
>  	}
>  }
>  
> -static inline unsigned int resctrl_arch_round_mon_val(unsigned int val)
> -{
> -	unsigned int scale = boot_cpu_data.x86_cache_occ_scale;
> -
> -	/* h/w works in units of "boot_cpu_data.x86_cache_occ_scale" */
> -	val /= scale;
> -	return val * scale;
> -}
> -
>  static inline void resctrl_arch_set_cpu_default_closid_rmid(int cpu, u32 closid,
>  							    u32 rmid)
>  {
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 6e46f10d8640..e42ee2769a39 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -421,6 +421,15 @@ __init void resctrl_arch_update_snc(void)
>  	snc_nodes_per_l3_cache = snc_get_config();
>  }
>  
> +unsigned int resctrl_arch_round_mon_val(unsigned int val)
> +{
> +	unsigned int scale = boot_cpu_data.x86_cache_occ_scale;
> +
> +	/* h/w works in units of "boot_cpu_data.x86_cache_occ_scale" */
> +	val /= scale;
> +	return val * scale;
> +}
> +
>  int __init rdt_get_l3_mon_config(struct rdt_resource *r)
>  {
>  	unsigned int mbm_offset = boot_cpu_data.x86_cache_mbm_width_offset;
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 9d223057953a..5799c6bd4f98 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -143,6 +143,11 @@ void resctrl_arch_pre_mount(void)
>  {
>  }
>  
> +unsigned int resctrl_arch_round_mon_val(unsigned int val)
> +{
> +	return val;
> +}
> +
>  bool resctrl_arch_get_cdp_enabled(enum resctrl_res_level rid)
>  {
>  	return mpam_resctrl_controls[rid].cdp_enabled;
> diff --git a/include/linux/arm_mpam.h b/include/linux/arm_mpam.h
> index f92a36187a52..4c639e9c8e5b 100644
> --- a/include/linux/arm_mpam.h
> +++ b/include/linux/arm_mpam.h
> @@ -76,11 +76,6 @@ static inline void resctrl_arch_disable_mon(void) { }
>  static inline void resctrl_arch_enable_alloc(void) { }
>  static inline void resctrl_arch_disable_alloc(void) { }
>  
> -static inline unsigned int resctrl_arch_round_mon_val(unsigned int val)
> -{
> -	return val;
> -}
> -
>  /**
>   * mpam_register_requestor() - Register a requestor with the MPAM driver
>   * @partid_max:		The maximum PARTID value the requestor can generate.
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index dd09c2ce9a0f..c99561b19e7a 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -418,6 +418,7 @@ static inline u32 resctrl_get_default_ctrl(struct rdt_resource *r)
>  u32 resctrl_arch_get_num_closid(struct rdt_resource *r);
>  u32 resctrl_arch_system_num_rmid_idx(void);
>  int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid);
> +unsigned int resctrl_arch_round_mon_val(unsigned int val);
>  
>  bool resctrl_enable_mon_event(enum resctrl_event_id eventid, bool any_cpu,
>  			      unsigned int binary_bits, void *arch_priv);