linux-kernel - Re: [PATCH v6 20/21] x86/resctrl: Add resctrl_rmid_realloc_limit to abstract x86's boot_cpu

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Date:   Wed, 7 Sep 2022 14:26:57 +0800
From:   haoxin <xhao@...ux.alibaba.com>
To:     James Morse <james.morse@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        shameerali.kolothum.thodi@...wei.com,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        lcherian@...vell.com, bobo.shaobowang@...wei.com,
        tan.shaopeng@...itsu.com, Jamie Iles <quic_jiles@...cinc.com>,
        Cristian Marussi <cristian.marussi@....com>,
        xingxin.hx@...nanolis.org, baolin.wang@...ux.alibaba.com
Subject: Re: [PATCH v6 20/21] x86/resctrl: Add resctrl_rmid_realloc_limit to
 abstract x86's boot_cpu_data


在 2022/9/2 下午11:48, James Morse 写道:
> resctrl_rmid_realloc_threshold can be set by user-space. The maximum
> value is specified by the architecture.
>
> Currently max_threshold_occ_write() reads the maximum value from
> boot_cpu_data.x86_cache_size, which is not portable to another
> architecture.
>
> Add resctrl_rmid_realloc_limit to describe the maximum size in bytes
> that user-space can set the threshold to.
>
> Reviewed-by: Jamie Iles <quic_jiles@...cinc.com>
> Tested-by: Xin Hao <xhao@...ux.alibaba.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Tested-by: Cristian Marussi <cristian.marussi@....com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> Signed-off-by: James Morse <james.morse@....com>
> ---
>   arch/x86/kernel/cpu/resctrl/monitor.c  | 9 +++++++--
>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 2 +-
>   include/linux/resctrl.h                | 1 +
>   3 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index e91afe99b763..8d15568d7121 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -67,6 +67,11 @@ unsigned int rdt_mon_features;
>    */
>   unsigned int resctrl_rmid_realloc_threshold;
>   
> +/*
> + * This is the maximum value for the reallocation threshold, in bytes.
> + */
> +unsigned int resctrl_rmid_realloc_limit;
> +
>   #define CF(cf)	((unsigned long)(1048576 * (cf) + 0.5))
>   
>   /*
> @@ -747,10 +752,10 @@ int rdt_get_mon_l3_config(struct rdt_resource *r)
>   {
>   	unsigned int mbm_offset = boot_cpu_data.x86_cache_mbm_width_offset;
>   	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> -	unsigned int cl_size = boot_cpu_data.x86_cache_size;
>   	unsigned int threshold;
>   	int ret;
>   
> +	resctrl_rmid_realloc_limit = boot_cpu_data.x86_cache_size * 1024;
Use SZ_1K instead ?
>   	hw_res->mon_scale = boot_cpu_data.x86_cache_occ_scale;
>   	r->num_rmid = boot_cpu_data.x86_cache_max_rmid + 1;
>   	hw_res->mbm_width = MBM_CNTR_WIDTH_BASE;
> @@ -767,7 +772,7 @@ int rdt_get_mon_l3_config(struct rdt_resource *r)
>   	 *
>   	 * For a 35MB LLC and 56 RMIDs, this is ~1.8% of the LLC.
>   	 */
> -	threshold = cl_size * 1024 / r->num_rmid;
> +	threshold = resctrl_rmid_realloc_limit / r->num_rmid;
>   
>   	/*
>   	 * Because num_rmid may not be a power of two, round the value
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 849bdec37217..e5a48f05e787 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1059,7 +1059,7 @@ static ssize_t max_threshold_occ_write(struct kernfs_open_file *of,
>   	if (ret)
>   		return ret;
>   
> -	if (bytes > (boot_cpu_data.x86_cache_size * 1024))
> +	if (bytes > resctrl_rmid_realloc_limit)
>   		return -EINVAL;
>   
>   	resctrl_rmid_realloc_threshold = resctrl_arch_round_mon_val(bytes);
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 9995d043650a..cb857f753322 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -251,5 +251,6 @@ void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_domain *d,
>   			     u32 rmid, enum resctrl_event_id eventid);
>   
>   extern unsigned int resctrl_rmid_realloc_threshold;
> +extern unsigned int resctrl_rmid_realloc_limit;
>   
>   #endif /* _RESCTRL_H */