linux-kernel - Re: [PATCH v19 00/20] Add support for Sub-NUMA cluster (SNC) systems

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Date: Wed, 29 May 2024 13:20:30 -0700
From: Tony Luck <tony.luck@...el.com>
To: Reinette Chatre <reinette.chatre@...el.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>,
	Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>,
	Peter Newman <peternewman@...gle.com>,
	James Morse <james.morse@....com>, Babu Moger <babu.moger@....com>,
	Drew Fustini <dfustini@...libre.com>,
	Dave Martin <Dave.Martin@....com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH v19 00/20] Add support for Sub-NUMA cluster (SNC) systems

On Tue, May 28, 2024 at 03:55:29PM -0700, Reinette Chatre wrote:
> Hi Tony,
> > 13:	Wordsmith commit into imperative.
> > 	I looked at using kobject_has_children() to check for empty
> > 	directory, but it needs a "struct kobject *" and all I have
> > 	is "struct kernfs_node *". I'm now checking how many CPUs
> 
> Consider how kobject_has_children() uses that struct kobject *.
> Specifically:
> 	return kobj->sd && kobj->sd->dir.subdirs
> 
> It operates on kobj->sd, which is exactly what you have: struct kernfs_node.

So right. My turn to grumble about other peoples choice of names. If
that field was named "kn" instead of "sd" I would have spotted this
too.

> > 	remain in ci->shared_cpu_map to detect whether this is the
> > 	last SNC node.
> 
> hmmm, ok, will take a look ... but please finalize discussion of a patch series
> before submitting a new series that rejects feedback without discussion and
> does something completely different in new version.

Reinette,

So here's what rmdir_mondata_subdir_allrdtgrp() looks like using the
subdirs check. It might need an update/better header comment.

-Tony

---

/*
 * Remove all subdirectories of mon_data of ctrl_mon groups
 * and monitor groups with given domain id.
 */
static void rmdir_mondata_subdir_allrdtgrp(struct rdt_resource *r,
					   struct rdt_mon_domain *d)
{
	struct rdtgroup *prgrp, *crgrp;
	struct kernfs_node *kn;
	char subname[32];
	char name[32];

	sprintf(name, "mon_%s_%02d", r->name, d->ci->id);
	if (r->mon_scope != RESCTRL_L3_CACHE) {
		/*
		 * SNC mode: Unless the last domain is being removed must
		 * just remove the SNC subdomain.
		 */
		sprintf(subname, "mon_sub_%s_%02d", r->name, d->hdr.id);
	}

	list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
		kn = kernfs_find_and_get(prgrp->mon.mon_data_kn, name);
		if (!kn)
			continue;

		if (kn->dir.subdirs <= 1)
			kernfs_remove(kn);
		else
			kernfs_remove_by_name(kn, subname);

		list_for_each_entry(crgrp, &prgrp->mon.crdtgrp_list, mon.crdtgrp_list) {
			kn = kernfs_find_and_get(crgrp->mon.mon_data_kn, name);
			if (!kn)
				continue;

			if (kn->dir.subdirs <= 1)
				kernfs_remove(kn);
			else
				kernfs_remove_by_name(kn, subname);
		}
	}
}