linux-kernel - Re: [RFC PATCH v2 11/17] sched: Basic tracking of matching tasks

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Date:   Mon, 29 Apr 2019 14:15:18 +0800
From:   Aaron Lu <aaron.lu@...ux.alibaba.com>
To:     Vineeth Remanan Pillai <vpillai@...italocean.com>
Cc:     Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>, mingo@...nel.org,
        tglx@...utronix.de, pjt@...gle.com, torvalds@...ux-foundation.org,
        linux-kernel@...r.kernel.org, subhra.mazumdar@...cle.com,
        fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com,
        Phil Auld <pauld@...hat.com>, Aaron Lu <aaron.lwe@...il.com>,
        Aubrey Li <aubrey.intel@...il.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [RFC PATCH v2 11/17] sched: Basic tracking of matching tasks

On Tue, Apr 23, 2019 at 04:18:16PM +0000, Vineeth Remanan Pillai wrote:
> +/*
> + * Find left-most (aka, highest priority) task matching @cookie.
> + */
> +struct task_struct *sched_core_find(struct rq *rq, unsigned long cookie)
> +{
> +	struct rb_node *node = rq->core_tree.rb_node;
> +	struct task_struct *node_task, *match;
> +
> +	/*
> +	 * The idle task always matches any cookie!
> +	 */
> +	match = idle_sched_class.pick_task(rq);
> +
> +	while (node) {
> +		node_task = container_of(node, struct task_struct, core_node);
> +
> +		if (node_task->core_cookie < cookie) {
> +			node = node->rb_left;

Should go right here?

> +		} else if (node_task->core_cookie > cookie) {
> +			node = node->rb_right;

And left here?

> +		} else {
> +			match = node_task;
> +			node = node->rb_left;
> +		}
> +	}
> +
> +	return match;
> +}