linux-kernel - Re: [PATCH v2 1/2] sched: make each sched class handle its rq assignment in their own class

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]

Date:	Wed, 14 Oct 2015 11:00:16 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	byungchul.park@....com
Cc:	mingo@...nel.org, linux-kernel@...r.kernel.org,
	yuyang.du@...el.com, pjt@...gle.com, efault@....de,
	tglx@...utronix.de
Subject: Re: [PATCH v2 1/2] sched: make each sched class handle its rq
 assignment in their own class

On Wed, Oct 14, 2015 at 05:42:09PM +0900, byungchul.park@....com wrote:
> +static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
> +{
> +	const struct sched_class *class;
> +
> +	for_each_class(class) {
> +		if (class->set_task_rq)
> +			class->set_task_rq(p, cpu);
> +	}
> +}

So I worry about this, because the class structures are not all in the
same translation unit, GCC cannot (without -fwhole-program) optimize
that all away.

This means we'll do 5 cacheline loads and 2 indirect calls, on _every_
cpu migration.
--
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/