Re: [PATCH v5 19/20] x86/resctrl: Introduce interface to list monitor states of all the groups

[Reinette Chatre]

Hi Babu,

On 7/3/24 2:48 PM, Babu Moger wrote:
> Provide the interface to list the monitor states of all the resctrl
> groups in ABMC mode.
>
> Example:
> $cat /sys/fs/resctrl/info/L3_MON/mbm_control
>
> List follows the following format:
>
> "<CTRL_MON group>/<MON group>/<domain_id>=<flags>"
>
> Format for specific type of groups:
>
> - Default CTRL_MON group:
>    "//<domain_id>=<flags>"
>
> - Non-default CTRL_MON group:
>    "<CTRL_MON group>//<domain_id>=<flags>"
>
> - Child MON group of default CTRL_MON group:
>    "/<MON group>/<domain_id>=<flags>"
>
> - Child MON group of non-default CTRL_MON group:
>    "<CTRL_MON group>/<MON group>/<domain_id>=<flags>"
>
>
> Flags can be one of the following:
> t  MBM total event is enabled
> l  MBM local event is enabled
> tl Both total and local MBM events are enabled
> _  None of the MBM events are enabled
>
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> ---
> v5: Replaced "assignment flags" with "flags".
>      Changes related to mon structure.
>      Changes related renaming the interface from mbm_assign_control to
>      mbm_control.
>
> v4: Added functionality to query domain specific assigment in.
>      rdtgroup_abmc_dom_state().
>
> v3: New patch.
>      Addresses the feedback to provide the global assignment interface.
>      https://lore.kernel.org/lkml/c73f444b-83a1-4e9a-95d3-54c5165ee782@xxxxxxxxx/
> ---
>   Documentation/arch/x86/resctrl.rst     |  54 ++++++++++
>   arch/x86/kernel/cpu/resctrl/monitor.c  |   1 +
>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 130 +++++++++++++++++++++++++
>   3 files changed, 185 insertions(+)
>
> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> index 4c41c5622627..05fee779e109 100644
> --- a/Documentation/arch/x86/resctrl.rst
> +++ b/Documentation/arch/x86/resctrl.rst
> @@ -304,6 +304,60 @@ with the following files:
>   "num_mbm_cntrs":
>   	The number of monitoring counters available for assignment.
>   
> +"mbm_control":
> +	Available when ABMC features are supported.

"Available when ABMC features are supported." can be dropped

> +	Reports the resctrl group and monitor status of each group.
> +
> +	List follows the following format:
> +		"<CTRL_MON group>/<MON group>/<domain_id>=<flags>"
> +
> +	Format for specific type of grpups:

grpups -> groups

> +
> +	* Default CTRL_MON group:
> +		"//<domain_id>=<flags>"
> +
> +	* Non-default CTRL_MON group:
> +		"<CTRL_MON group>//<domain_id>=<flags>"
> +
> +	* Child MON group of default CTRL_MON group:
> +		"/<MON group>/<domain_id>=<flags>"
> +
> +	* Child MON group of non-default CTRL_MON group:
> +		"<CTRL_MON group>/<MON group>/<domain_id>=<flags>"
> +
> +	Flags can be one of the following:
> +	::
> +
> +	 t  MBM total event is enabled.
> +	 l  MBM local event is enabled.
> +	 tl Both total and local MBM events are enabled.
> +	 _  None of the MBM events are enabled.
> +
> +	Examples:
> +	::
> +
> +	 # mkdir /sys/fs/resctrl/mon_groups/child_default_mon_grp
> +	 # mkdir /sys/fs/resctrl/non_default_ctrl_mon_grp
> +	 # mkdir /sys/fs/resctrl/non_default_ctrl_mon_grp/mon_groups/child_non_default_mon_grp
> +
> +	 # cat /sys/fs/resctrl/info/L3_MON/mbm_control
> +	 non_default_ctrl_mon_grp//0=tl;1=tl;
> +	 non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=tl;
> +	 //0=tl;1=tl;
> +	 /child_default_mon_grp/0=tl;1=tl;
> +
> +	 There are four resctrl groups. All the groups have total and local events are
> +	 enabled on domain 0 and 1.

"All the groups have total and local events are enabled" -> "All the groups have total and local events enabled"?

> +

The text below seems to repeat ealier description.

> +	 non_default_ctrl_mon_grp// - This is a non-default CTRL_MON group.
> +
> +	 non_default_ctrl_mon_grp/child_non_default_mon_grp/ - This is a child monitor
> +	 group of non-default CTRL_MON group.
> +
> +	 // - This is a default CTRL_MON group.
> +
> +	 /child_default_mon_grp/ - This is a child monitor group of default CTRL_MON group.
> +
>   "max_threshold_occupancy":
>   		Read/write file provides the largest value (in
>   		bytes) at which a previously used LLC_occupancy
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index b96b0a8bd7d3..684730f1a72d 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -1244,6 +1244,7 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
>   				r->mon.num_mbm_cntrs = 64;
>   
>   			resctrl_file_fflags_init("num_mbm_cntrs", RFTYPE_MON_INFO);
> +			resctrl_file_fflags_init("mbm_control", RFTYPE_MON_INFO);

Shouldn't this file always be present?

>   		}
>   	}
>   
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index d978668c8865..0de9f23d5389 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -944,6 +944,130 @@ static ssize_t rdtgroup_mbm_mode_write(struct kernfs_open_file *of,
>   	return ret ?: nbytes;
>   }
>   
> +static void rdtgroup_abmc_dom_cfg(void *info)
> +{
> +	u64 *msrval = info;
> +
> +	wrmsrl(MSR_IA32_L3_QOS_ABMC_CFG, *msrval);
> +	rdmsrl(MSR_IA32_L3_QOS_ABMC_DSC, *msrval);
> +}
> +
> +/*
> + * Writing the counter id with CfgEn=0 on L3_QOS_ABMC_CFG and reading
> + * L3_QOS_ABMC_DSC back will return configuration of the counter
> + * specified.

Can this be expanded to explain what the return values mean?

> + */
> +static int rdtgroup_abmc_dom_state(struct rdt_mon_domain *d, u32 cntr_id,
> +				   u32 rmid)
> +{
> +	union l3_qos_abmc_cfg abmc_cfg = { 0 };
> +
> +	abmc_cfg.split.cfg_en = 0;
> +	abmc_cfg.split.cntr_id = cntr_id;
> +
> +	smp_call_function_any(&d->hdr.cpu_mask, rdtgroup_abmc_dom_cfg,
> +			      &abmc_cfg, 1);
> +
> +	if (abmc_cfg.split.cntr_en && abmc_cfg.split.bw_src == rmid)
> +		return 0;
> +	else
> +		return -1;
> +}
> +
> +static char *rdtgroup_mon_state_to_str(struct rdtgroup *rdtgrp,
> +				       struct rdt_mon_domain *d, char *str)
> +{
> +	char *tmp = str;
> +	int dom_state = ASSIGN_NONE;

reverse fir

> +
> +	/*
> +	 * Query the monitor state for the domain.
> +	 * Index 0 for evtid == QOS_L3_MBM_TOTAL_EVENT_ID
> +	 * Index 1 for evtid == QOS_L3_MBM_LOCAL_EVENT_ID

Why not use the helper?

> +	 */
> +	if (rdtgrp->mon.cntr_id[0] != MON_CNTR_UNSET)
> +		if (!rdtgroup_abmc_dom_state(d, rdtgrp->mon.cntr_id[0], rdtgrp->mon.rmid))
> +			dom_state |= ASSIGN_TOTAL;
> +
> +	if (rdtgrp->mon.cntr_id[1] != MON_CNTR_UNSET)
> +		if (!rdtgroup_abmc_dom_state(d, rdtgrp->mon.cntr_id[1], rdtgrp->mon.rmid))
> +			dom_state |= ASSIGN_LOCAL;
> +
> +	switch (dom_state) {
> +	case ASSIGN_NONE:
> +		*tmp++ = '_';
> +		break;
> +	case (ASSIGN_TOTAL | ASSIGN_LOCAL):
> +		*tmp++ = 't';
> +		*tmp++ = 'l';
> +		break;
> +	case ASSIGN_TOTAL:
> +		*tmp++ = 't';
> +		break;
> +	case ASSIGN_LOCAL:
> +		*tmp++ = 'l';
> +		break;
> +	default:
> +		break;
> +	}

This switch statement does not scale. Adding new flags will be painful. Can flags not
just incrementally be printed as learned from hardware with "_" printed as last resort?
This would elimininate need for these "ASSIGN" flags.

> +
> +	*tmp = '\0';
> +	return str;
> +}
> +
> +static int rdtgroup_mbm_control_show(struct kernfs_open_file *of,
> +				     struct seq_file *s, void *v)
> +{
> +	struct rdt_resource *r = of->kn->parent->priv;
> +	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> +	struct rdt_mon_domain *dom;
> +	struct rdtgroup *rdtg;
> +	int grp_default = 0;
> +	char str[10];
> +
> +	if (!hw_res->abmc_enabled) {
> +		rdt_last_cmd_puts("ABMC feature is not enabled\n");
> +		return -EINVAL;
> +	}
> +
> +	mutex_lock(&rdtgroup_mutex);
> +
> +	list_for_each_entry(rdtg, &rdt_all_groups, rdtgroup_list) {
> +		struct rdtgroup *crg;
> +
> +		if (rdtg == &rdtgroup_default) {
> +			grp_default = 1;
> +			seq_puts(s, "//");
> +		} else {
> +			grp_default = 0;
> +			seq_printf(s, "%s//", rdtg->kn->name);
> +		}

Isn't the default resource group's name already empty string? That should
eliminate the need for this special handling, no?

> +
> +		list_for_each_entry(dom, &r->mon_domains, hdr.list)
> +			seq_printf(s, "%d=%s;", dom->hdr.id,
> +				   rdtgroup_mon_state_to_str(rdtg, dom, str));
> +		seq_putc(s, '\n');
> +
> +		list_for_each_entry(crg, &rdtg->mon.crdtgrp_list,
> +				    mon.crdtgrp_list) {
> +			if (grp_default)
> +				seq_printf(s, "/%s/", crg->kn->name);
> +			else
> +				seq_printf(s, "%s/%s/", rdtg->kn->name,
> +					   crg->kn->name);
> +

Same here .... with default group having name of empty string it can just be
printed directly, no?

> +			list_for_each_entry(dom, &r->mon_domains, hdr.list)
> +				seq_printf(s, "%d=%s;", dom->hdr.id,
> +					   rdtgroup_mon_state_to_str(crg, dom, str));
> +			seq_putc(s, '\n');
> +		}
> +	}
> +
> +	mutex_unlock(&rdtgroup_mutex);
> +
> +	return 0;
> +}
> +
>   #ifdef CONFIG_PROC_CPU_RESCTRL
>   
>   /*
> @@ -2156,6 +2280,12 @@ static struct rftype res_common_files[] = {
>   		.kf_ops		= &rdtgroup_kf_single_ops,
>   		.seq_show	= rdtgroup_num_mbm_cntrs_show,
>   	},
> +	{
> +		.name		= "mbm_control",
> +		.mode		= 0444,
> +		.kf_ops		= &rdtgroup_kf_single_ops,
> +		.seq_show	= rdtgroup_mbm_control_show,
> +	},
>   	{
>   		.name		= "cpus_list",
>   		.mode		= 0644,

Reinette