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 18:26:30 +0900
From:	Byungchul Park <byungchul.park@....com>
To:	Peter Zijlstra <peterz@...radead.org>
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 11:00:16AM +0200, Peter Zijlstra wrote:
> 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.

i wondered if it was so, and it was.

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

i agree with your this concern. to avoid this concern, it can be done by
hard coding as current code.. but we will lose code flexability. i thought
migration overhead was not so important since it hardly happens.

> --
> 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/
--
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/