Re: [PATCH v5 15/20] x86/resctrl: Assign/unassign counters by default when ABMC is enabled

[Reinette Chatre]

Hi Babu,

On 7/3/24 2:48 PM, Babu Moger wrote:
> Assign/unassign counters on resctrl group creation/deletion. If the
> counters are exhausted, report the warnings and continue. It is not
> required to fail group creation for assignment failures. Users have
> the option to modify the assignments later.
>
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> ---
> v5: Removed the code to enable/disable ABMC during the mount.
>      That will be another patch.
>      Added arch callers to get the arch specific data.
>      Renamed fuctions to match the other abmc function.
>      Added code comments for assignment failures.
>
> v4: Few name changes based on the upstream discussion.
>      Commit message update.
>
> v3: This is a new patch. Patch addresses the upstream comment to enable
>      ABMC feature by default if the feature is available.
> ---
>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 78 ++++++++++++++++++++++++++
>   1 file changed, 78 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index ffde30b36c1a..475a0c7b2a25 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -2910,6 +2910,46 @@ static void schemata_list_destroy(void)
>   	}
>   }
>   
> +/*
> + * Called when new group is created. Assign the counters if ABMC is
> + * already enabled. Two counters are required per group, one for total
> + * event and one for local event. With limited number of counters,
> + * the assignments can fail in some cases. But, it is not required to
> + * fail the group creation. Users have the option to modify the
> + * assignments after the group creation.
> + */
> +static int rdtgroup_assign_cntrs(struct rdtgroup *rdtgrp)
> +{
> +	int ret = 0;
> +
> +	if (!resctrl_arch_get_abmc_enabled())
> +		return 0;
> +
> +	if (is_mbm_total_enabled())
> +		ret = rdtgroup_assign_cntr(rdtgrp, QOS_L3_MBM_TOTAL_EVENT_ID);
> +
> +	if (!ret && is_mbm_local_enabled())
> +		ret = rdtgroup_assign_cntr(rdtgrp, QOS_L3_MBM_LOCAL_EVENT_ID);
> +
> +	return ret;
> +}
> +
> +static int rdtgroup_unassign_cntrs(struct rdtgroup *rdtgrp)
> +{
> +	int ret = 0;
> +
> +	if (!resctrl_arch_get_abmc_enabled())
> +		return 0;
> +
> +	if (is_mbm_total_enabled())
> +		ret = rdtgroup_unassign_cntr(rdtgrp, QOS_L3_MBM_TOTAL_EVENT_ID);
> +
> +	if (!ret && is_mbm_local_enabled())
> +		ret = rdtgroup_unassign_cntr(rdtgrp, QOS_L3_MBM_LOCAL_EVENT_ID);
> +
> +	return ret;
> +}
> +
>   static int rdt_get_tree(struct fs_context *fc)
>   {
>   	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> @@ -2972,6 +3012,16 @@ static int rdt_get_tree(struct fs_context *fc)
>   		if (ret < 0)
>   			goto out_mongrp;
>   		rdtgroup_default.mon.mon_data_kn = kn_mondata;
> +
> +		/*
> +		 * Assign the counters if ABMC is already enabled.
> +		 * With limited number of counters, the assignments can
> +		 * fail in some cases. But, it is not required to fail
> +		 * the group creation. Users have the option to modify
> +		 * the assignments after the group creation.
> +		 */

The function has detailed comments - it seems unnecessary to me that the
same comments are duplicated at each call site.

> +		if (rdtgroup_assign_cntrs(&rdtgroup_default) < 0)
> +			rdt_last_cmd_puts("Monitor assignment failed\n");

rdtgroup_assign_cntrs() already prints message, why print another? Error
handling can then be dropped.

>   	}
>   
>   	ret = rdt_pseudo_lock_init();
> @@ -3246,6 +3296,8 @@ static void rdt_kill_sb(struct super_block *sb)
>   	cpus_read_lock();
>   	mutex_lock(&rdtgroup_mutex);
>   
> +	rdtgroup_unassign_cntrs(&rdtgroup_default);
> +

This seems appropriate to be in the "Put everything back to default values"
section.

>   	rdt_disable_ctx();
>   
>   	/*Put everything back to default values. */
> @@ -3850,6 +3902,16 @@ static int rdtgroup_mkdir_mon(struct kernfs_node *parent_kn,
>   		goto out_unlock;
>   	}
>   
> +	/*
> +	 * Assign the counters if ABMC is already enabled.
> +	 * With the limited number of counters, there can be cases
> +	 * only on assignment succeed. It is not required to fail
> +	 * here in that case. Users have the option to modify the
> +	 * assignments later.
> +	 */
> +	if (rdtgroup_assign_cntrs(rdtgrp) < 0)
> +		rdt_last_cmd_puts("Monitor assignment failed\n");
> +
>   	kernfs_activate(rdtgrp->kn);
>   
>   	/*
> @@ -3894,6 +3956,17 @@ static int rdtgroup_mkdir_ctrl_mon(struct kernfs_node *parent_kn,
>   	if (ret)
>   		goto out_closid_free;
>   
> +	/*
> +	 * Assign the counters if ABMC is already enabled.
> +	 * With the limited number of counters, there can be cases
> +	 * only on assignment succeed. It is not required to fail
> +	 * here in that case. Users have the option to assign the
> +	 * counter later.
> +	 */
> +
> +	if (rdtgroup_assign_cntrs(rdtgrp) < 0)
> +		rdt_last_cmd_puts("Monitor assignment failed\n");
> +
>   	kernfs_activate(rdtgrp->kn);
>   
>   	ret = rdtgroup_init_alloc(rdtgrp);
> @@ -3989,6 +4062,9 @@ static int rdtgroup_rmdir_mon(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
>   	update_closid_rmid(tmpmask, NULL);
>   
>   	rdtgrp->flags = RDT_DELETED;
> +
> +	rdtgroup_unassign_cntrs(rdtgrp);
> +
>   	free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
>   
>   	/*
> @@ -4035,6 +4111,8 @@ static int rdtgroup_rmdir_ctrl(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
>   	cpumask_or(tmpmask, tmpmask, &rdtgrp->cpu_mask);
>   	update_closid_rmid(tmpmask, NULL);
>   
> +	rdtgroup_unassign_cntrs(rdtgrp);
> +
>   	free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
>   	closid_free(rdtgrp->closid);
>   

Reinette