linux-kernel - Re: [PATCH 10/19] sched/fair: Prioritize tasks preferring destination LLC during balancing

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 for Android: free password hash cracker in your pocket

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

Message-ID: <576e63aa-3b39-4d05-87d3-e894ab57dcd1@amd.com>
Date: Mon, 27 Oct 2025 11:59:00 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Tim Chen <tim.c.chen@...ux.intel.com>, Peter Zijlstra
	<peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, "Gautham R . Shenoy"
	<gautham.shenoy@....com>
CC: Vincent Guittot <vincent.guittot@...aro.org>, Juri Lelli
	<juri.lelli@...hat.com>, Dietmar Eggemann <dietmar.eggemann@....com>, "Steven
 Rostedt" <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman
	<mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>, "Madadi Vineeth
 Reddy" <vineethr@...ux.ibm.com>, Hillf Danton <hdanton@...a.com>, "Shrikanth
 Hegde" <sshegde@...ux.ibm.com>, Jianyong Wu <jianyong.wu@...look.com>, Yangyu
 Chen <cyy@...self.name>, Tingyin Duan <tingyin.duan@...il.com>, "Vern Hao"
	<vernhao@...cent.com>, Len Brown <len.brown@...el.com>, Aubrey Li
	<aubrey.li@...el.com>, Zhao Liu <zhao1.liu@...el.com>, Chen Yu
	<yu.chen.surf@...il.com>, Chen Yu <yu.c.chen@...el.com>, Libo Chen
	<libo.chen@...cle.com>, Adam Li <adamli@...amperecomputing.com>, Tim Chen
	<tim.c.chen@...el.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 10/19] sched/fair: Prioritize tasks preferring destination
 LLC during balancing

Hello Tim,

On 10/11/2025 11:54 PM, Tim Chen wrote:
> +/*
> + * Do LLC balance on sched group that contains LLC, and have tasks preferring
> + * to run on LLC in idle dst_cpu.
> + */
> +static inline bool llc_balance(struct lb_env *env, struct sg_lb_stats *sgs,
> +			       struct sched_group *group)
> +{
> +	struct sched_domain *child = env->sd->child;
> +	int llc;
> +
> +	if (!sched_cache_enabled())
> +		return false;
> +
> +	if (env->sd->flags & SD_SHARE_LLC)
> +		return false;
> +
> +	/* only care about task migration among LLCs */
> +	if (child && !(child->flags & SD_SHARE_LLC))

nit. You can just check group->flags here.

> +		return false;
> +
> +	llc = llc_idx(env->dst_cpu);
> +	if (sgs->nr_pref_llc[llc] > 0 &&
> +	    can_migrate_llc(env->src_cpu, env->dst_cpu, 0, true) == mig_llc)
> +		return true;
> +
> +	return false;
> +}
>  #else
>  static inline void record_sg_llc_stats(struct lb_env *env, struct sg_lb_stats *sgs,
>  				       struct sched_group *group)
>  {
>  }
> +
> +static inline bool llc_balance(struct lb_env *env, struct sg_lb_stats *sgs,
> +			       struct sched_group *group)
> +{
> +	return false;
> +}
>  #endif
>  
>  /**
> @@ -10954,6 +10988,11 @@ static inline void update_sg_lb_stats(struct lb_env *env,
>  	sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
>  
>  	record_sg_llc_stats(env, sgs, group);

Okay, I see the intention of recording this based on group stats.
Sorry for the noise on Patch 2.

> +
> +	/* Check for tasks in this group can be moved to their preferred LLC */
> +	if (!local_group && llc_balance(env, sgs, group))
> +		sgs->group_llc_balance = 1;
> +
>  	/* Computing avg_load makes sense only when group is overloaded */
>  	if (sgs->group_type == group_overloaded)
>  		sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /

-- 
Thanks and Regards,
Prateek