linux-kernel - Re: [RFC 1/1] Weighted approach to gather and use history in TEO governor

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Message-ID: <20200512173722.GM2978@hirez.programming.kicks-ass.net>
Date:   Tue, 12 May 2020 19:37:22 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Pratik Rajesh Sampat <psampat@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        rafael.j.wysocki@...el.com, dsmythies@...us.net,
        daniel.lezcano@...aro.org, ego@...ux.vnet.ibm.com,
        svaidy@...ux.ibm.com, pratik.sampat@...ibm.com,
        pratik.r.sampat@...il.com
Subject: Re: [RFC 1/1] Weighted approach to gather and use history in TEO
 governor


Just a quick note..

On Mon, May 11, 2020 at 07:40:55PM +0530, Pratik Rajesh Sampat wrote:

> +	/*
> +	 * Rearrange the weight distribution of the state, increase the weight
> +	 * by the LEARNING RATE % for the idle state that was supposed to be
> +	 * chosen and reduce by the same amount for rest of the states
> +	 *
> +	 * If the weights are greater than (100 - LEARNING_RATE) % or lesser
> +	 * than LEARNING_RATE %, do not increase or decrease the confidence
> +	 * respectively
> +	 */
> +	for (i = 0; i < drv->state_count; i++) {
> +		unsigned int delta;
> +
> +		if (idx == -1)
> +			break;
> +		if (i ==  idx) {
> +			delta = (LEARNING_RATE * cpu_data->state_mat[last_idx][i]) / 100;

100 is a crap number to divide by as a computer. We bio-puddings happend
to have 10 digits, so 100 makes sense to us, but it does not to our
binary friends.