linux-kernel - Re: task_non_contending() for fair

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] [day] [month] [year] [list]

Message-ID: <87ldomkgcg.fsf@miraculix.mork.no>
Date: Thu, 17 Jul 2025 17:05:35 +0200
From: Bjørn Mork <bjorn@...k.no>
To: Juri Lelli <juri.lelli@...hat.com>
Cc: markus.stockhausen@....de, peterz@...radead.org,
        'Chris Packham' <Chris.Packham@...iedtelesis.co.nz>, mingo@...hat.com,
        vincent.guittot@...aro.org, anna-maria@...utronix.de,
        frederic@...nel.org, tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: task_non_contending() for fair_server leads to timer retries

Juri Lelli <juri.lelli@...hat.com> writes:
> On 15/07/25 16:39, markus.stockhausen@....de wrote:
>> Hi Peter,
>> 
>> I'm currently investigating issues with the timer-rtl-otto driver in 
>> 6.12 longterm on the Realtek MIPS switch platform (Chris is working
>> hard to upstream this). While doing so I observed that timer retries 
>> continually increase (~6/second) according to /proc/timer_list. The 
>> system is otherwise totally idle. 6.6 longterm does not show that issue.
>> I'm unsure if this is related but documentation reads like "that's bad". 
>> 
>> To be sure about this one I nailed it down to the fair server.
>
> Apologies for interjecting before Peter had a chance to reply, but I had
> a first look and I wonder if this recent patch from Peter (on
> tip/sched/core atm) can already help with the issue, as it should
> reduce the number of dl-server dequeues:
>
> cccb45d7c4295 ("sched/deadline: Less agressive dl_server handling")
>
> Can you please check what you see with it?

Spot on.  Thanks
 
I tested cccb45d7c4295 ("sched/deadline: Less agressive dl_server
handling") on top of the 6.12 longterm we're running and the retries
rate is back to "normal".


Bjørn