linux-kernel - Re: [PATCH] sched/deadline: Do not start hrtick if its disabled for DL

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]

Message-ID: <ZzMI9dYjWKqNtQzv@jlelli-thinkpadt14gen4.remote.csb>
Date: Tue, 12 Nov 2024 07:51:17 +0000
From: Juri Lelli <juri.lelli@...hat.com>
To: "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Valentin Schneider <vschneid@...hat.com>,
	Aashish Sharma <shraash@...gle.com>,
	Vineeth Pillai <vineeth@...byteword.org>
Subject: Re: [PATCH] sched/deadline: Do not start hrtick if its disabled for
 DL

Hi Joel,

On 12/11/24 01:22, Joel Fernandes (Google) wrote:
> Fix an issue where high-resolution timers causes aggressive preemptions,
> leading to increased idle times in CFS tasks (which are inside the DL
> server). The problem was traced to improper usage of hrtick_enabled(),
> which could start high-resolution ticks unexpectedly causing repeated
> preemptions.
> 
> The fix replaces this call with hrtick_enabled_dl(), aligning it with
> scheduler feature checks.
> 
> Reported-by: Aashish Sharma <shraash@...gle.com>
> Reported-by: Vineeth Pillai <vineeth@...byteword.org>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> ---
>  kernel/sched/deadline.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index b216e6deeac4..d46502b9ce58 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -2121,7 +2121,7 @@ static struct task_struct *pick_next_task_dl(struct rq *rq)
>  	if (!p->dl_server)
>  		set_next_task_dl(rq, p, true);
>  
> -	if (hrtick_enabled(rq))
> +	if (hrtick_enabled_dl(rq))
>  		start_hrtick_dl(rq, &p->dl);
>  
>  	return p;
> -- 

I'm not sure I'm seeing this in current code. We have two users in
deadline.c and they both use hrtick_enabled_dl (after a recent fix by
Phil).

Best,
Juri