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, 04 Nov 2009 14:00:33 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	linux-kernel@...r.kernel.org, jens.axboe@...cle.com,
	nauman@...gle.com, dpshah@...gle.com, lizf@...fujitsu.com,
	ryov@...inux.co.jp, fernando@....ntt.co.jp, s-uchida@...jp.nec.com,
	taka@...inux.co.jp, guijianfeng@...fujitsu.com,
	balbir@...ux.vnet.ibm.com, righi.andrea@...il.com,
	m-ikeda@...jp.nec.com, akpm@...ux-foundation.org, riel@...hat.com,
	kamezawa.hiroyu@...fujitsu.com
Subject: Re: [PATCH 15/20] blkio: Take care of preemptions across groups

Vivek Goyal <vgoyal@...hat.com> writes:

> +static bool cfq_should_preempt_group(struct cfq_data *cfqd,
> +		struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
> +{
> +	struct cfq_entity *cfqe = &cfqq->entity;
> +	struct cfq_entity *new_cfqe = &new_cfqq->entity;
> +
> +	if (cfqq_to_cfqg(cfqq) != &cfqd->root_group)
> +		cfqe = parent_entity(&cfqq->entity);
> +
> +	if (cfqq_to_cfqg(new_cfqq) != &cfqd->root_group)
> +		new_cfqe = parent_entity(&new_cfqq->entity);
> +
> +	/*
> +	 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
> +	 */
> +
> +	if (new_cfqe->ioprio_class == IOPRIO_CLASS_RT
> +	    && cfqe->ioprio_class != IOPRIO_CLASS_RT)
> +		return true;
> +	/*
> +	 * Allow an BE request to pre-empt an ongoing IDLE clas timeslice.
> +	 */
> +
> +	if (new_cfqe->ioprio_class == IOPRIO_CLASS_BE
> +	    && cfqe->ioprio_class == IOPRIO_CLASS_IDLE)
> +		return true;
> +
> +	return false;
> +}

What was the motivation for this?  It seems like this would really break
isolation.  What if one group has all RT priority tasks, will it starve
out the other groups?

Cheers,
Jeff
--
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/

Powered by blists - more mailing lists