linux-kernel - Re: [PATCH 14/21] x86/intel_rdt/cqm: Add mon

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Date:   Sun, 2 Jul 2017 14:43:56 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Vikas Shivappa <vikas.shivappa@...ux.intel.com>
cc:     x86@...nel.org, linux-kernel@...r.kernel.org, hpa@...or.com,
        peterz@...radead.org, ravi.v.shankar@...el.com,
        vikas.shivappa@...el.com, tony.luck@...el.com,
        fenghua.yu@...el.com, andi.kleen@...el.com
Subject: Re: [PATCH 14/21] x86/intel_rdt/cqm: Add mon_data

On Mon, 26 Jun 2017, Vikas Shivappa wrote:

> Add a mon_data directory for the root rdtgroup and all other rdtgroups.
> The directory holds all of the monitored data for all domains and events
> of all resources being monitored.

Again. This does two things at once. Move the existing code to a new file
and add the monitoring stuff. Please split it apart.

> +static bool __mon_event_count(u32 rmid, struct rmid_read *rr)
> +{
> +	u64 tval;
> +
> +	tval = __rmid_read(rmid, rr->evtid);
> +	if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL)) {
> +		rr->val = tval;
> +		return false;
> +	}
> +	switch (rr->evtid) {
> +	case QOS_L3_OCCUP_EVENT_ID:
> +		rr->val += tval;
> +		return true;
> +	default:
> +		return false;

I have no idea what that return code means. 

> +	}
> +}
> +
> +void mon_event_count(void *info)

Some explanation why this is a void pointer and how that function is called
(I assume it's via IPI) would be appreciated.

> +{
> +	struct rdtgroup *rdtgrp, *entry;
> +	struct rmid_read *rr = info;
> +	struct list_head *llist;

  *head;

> +
> +	rdtgrp = rr->rgrp;
> +
> +	if (!__mon_event_count(rdtgrp->rmid, rr))
> +		return;
> +
> +	/*
> +	 * For Ctrl groups read data from child monitor groups.
> +	 */
> +	llist = &rdtgrp->crdtgrp_list;
> +
> +	if (rdtgrp->type == RDTCTRL_GROUP) {
> +		list_for_each_entry(entry, llist, crdtgrp_list) {
> +			if (!__mon_event_count(entry->rmid, rr))
> +				return;
> +		}
> +	}
> +}

> +static int get_rdt_resourceid(struct rdt_resource *r)
> +{
> +	if (r > (rdt_resources_all + RDT_NUM_RESOURCES - 1) ||
> +	    r < rdt_resources_all ||
> +	    ((r - rdt_resources_all) % sizeof(struct rdt_resource)))
> +		return -EINVAL;

If that ever happens, then you have other problems than a wrong pointer.

> +
> +	return ((r - rdt_resources_all) / sizeof(struct rdt_resource));

Moo. Can't you simply put an index field into struct rdt_resource,
intialize it with the resource ID and use that?

Thanks,

	tglx