linux-kernel - Re: [PATCH 5/8] sched: Favour moving tasks towards the preferred node

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: <20130627145245.GS28407@twins.programming.kicks-ass.net>
Date:	Thu, 27 Jun 2013 16:52:45 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/8] sched: Favour moving tasks towards the preferred node

On Wed, Jun 26, 2013 at 03:38:04PM +0100, Mel Gorman wrote:
> @@ -3897,6 +3907,28 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
>  	return delta < (s64)sysctl_sched_migration_cost;
>  }
>  
> +/* Returns true if the destination node has incurred more faults */
> +static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
> +{
> +	int src_nid, dst_nid;
> +
> +	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
> +		return false;
> +
> +	src_nid = cpu_to_node(env->src_cpu);
> +	dst_nid = cpu_to_node(env->dst_cpu);
> +
> +	if (src_nid == dst_nid)
> +		return false;
> +
> +	if (p->numa_migrate_seq < sysctl_numa_balancing_settle_count &&
> +	    p->numa_preferred_nid == dst_nid)
> +		return true;
> +
> +	return false;
> +}
> +
> +
>  /*
>   * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
>   */
> @@ -3945,10 +3977,14 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env)
>  
>  	/*
>  	 * Aggressive migration if:
> -	 * 1) task is cache cold, or
> -	 * 2) too many balance attempts have failed.
> +	 * 1) destination numa is preferred
> +	 * 2) task is cache cold, or
> +	 * 3) too many balance attempts have failed.
>  	 */
>  
> +	if (migrate_improves_locality(p, env))
> +		return 1;
> +
>  	tsk_cache_hot = task_hot(p, env->src_rq->clock_task, env->sd);
>  	if (!tsk_cache_hot ||
>  		env->sd->nr_balance_failed > env->sd->cache_nice_tries) {

Should we not also do the reverse; make it harder to worsen locality?

Similar to the task_hot() thing; do not allow to migrate a task on low
nr_balance_failed when it makes the locality worse.
--
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/