linux-kernel - Re: [RFCv3 PATCH 42/48] sched: Introduce energy awareness into find_busiest

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150324152104.GP21418@twins.programming.kicks-ass.net>
Date:	Tue, 24 Mar 2015 16:21:04 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Morten Rasmussen <morten.rasmussen@....com>
Cc:	mingo@...hat.com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, yuyang.du@...el.com,
	preeti@...ux.vnet.ibm.com, mturquette@...aro.org, nico@...aro.org,
	rjw@...ysocki.net, juri.lelli@....com, linux-kernel@...r.kernel.org
Subject: Re: [RFCv3 PATCH 42/48] sched: Introduce energy awareness into
 find_busiest_queue

On Wed, Feb 04, 2015 at 06:31:19PM +0000, Morten Rasmussen wrote:
> +++ b/kernel/sched/fair.c
> @@ -7216,6 +7216,37 @@ static struct rq *find_busiest_queue(struct lb_env *env,
>  	unsigned long busiest_load = 0, busiest_capacity = 1;
>  	int i;
>  
> +	if (env->use_ea) {
> +		struct rq *costliest = NULL;
> +		unsigned long costliest_usage = 1024, costliest_energy = 1;
> +
> +		for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
> +			unsigned long usage = get_cpu_usage(i);
> +			struct rq *rq = cpu_rq(i);
> +			struct sched_domain *sd = rcu_dereference(rq->sd);
> +			struct energy_env eenv = {
> +				.sg_top = sd->groups,
> +				.usage_delta    = 0,
> +				.src_cpu        = -1,
> +				.dst_cpu        = -1,
> +			};
> +			unsigned long energy = sched_group_energy(&eenv);
> +
> +			/*
> +			 * We're looking for the minimal cpu efficiency
> +			 * min(u_i / e_i), crosswise multiplication leads to
> +			 * u_i * e_j < u_j * e_i with j as previous minimum.
> +			 */
> +			if (usage * costliest_energy < costliest_usage * energy) {
> +				costliest_usage = usage;
> +				costliest_energy = energy;
> +				costliest = rq;
> +			}
> +		}
> +
> +		return costliest;
> +	}
> +
>  	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
>  		unsigned long capacity, wl;
>  		enum fbq_type rt;

So I've thought about parametrizing the whole load balance thing to
avoid things like this.

Irrespective of whether we balance on pure load or another metric we
have the same structure, only different units plugged in.

I've not really spend too much time on it to see what it would look
like, but I think it would be a good avenue to investigate to avoid
patches like this.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/