linux-kernel - Re: [PATCH 3/4] sched/fair: Consider SMT in ASYM

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: <YGxDcccJ1U9ru0kV@hirez.programming.kicks-ass.net>
Date:   Tue, 6 Apr 2021 13:18:09 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...nel.org>, Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.comi>, Mel Gorman <mgorman@...e.de>,
        Len Brown <len.brown@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        Quentin Perret <qperret@...gle.com>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        linux-kernel@...r.kernel.org, Aubrey Li <aubrey.li@...el.com>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: [PATCH 3/4] sched/fair: Consider SMT in ASYM_PACKING load balance

On Mon, Apr 05, 2021 at 09:11:07PM -0700, Ricardo Neri wrote:
> +static bool cpu_group_is_smt(int cpu, struct sched_group *sg)
> +{
> +#ifdef CONFIG_SCHED_SMT
> +	if (!static_branch_likely(&sched_smt_present))
> +		return false;
> +
> +	if (sg->group_weight == 1)
> +		return false;
> +
> +	if (cpumask_weight(cpu_smt_mask(cpu)) == 1)
> +		return false;

Please explain this condition. Why is it required?

> +	return cpumask_equal(sched_group_span(sg), cpu_smt_mask(cpu));
> +#else
> +	return false;
> +#endif
> +}