linux-kernel - Re: [PATCH 2/2] bcachefs: set rebalance thread to SCHED

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: <31baf43d-8d10-41f7-87ad-87e6d2150592@geekplace.eu>
Date: Tue, 14 Jan 2025 17:45:29 +0100
From: Florian Schmaus <flo@...kplace.eu>
To: Christian Loehle <christian.loehle@....com>
Cc: linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>, Mel Gorman <mgorman@...e.de>,
 Kent Overstreet <kent.overstreet@...ux.dev>,
 Valentin Schneider <vschneid@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>, Ben Segall
 <bsegall@...gle.com>, Steven Rostedt <rostedt@...dmis.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH 2/2] bcachefs: set rebalance thread to SCHED_BATCH and
 nice 19

On 14/01/2025 14.29, Christian Loehle wrote:
> On 1/14/25 12:47, Florian Schmaus wrote:
>> While the rebalance thread is isually not compute bound, it does cause
> 
> s/isually/usually
> 
>> a considerable amount of I/O. Since "reducing" the nice level from 0
>> to 19, also implicitly reduces the threads best-effort I/O scheduling
>> class level from 4 to 7, the reblance thread's I/O will be depriotized
> 
> s/depriotized/deprioritized/
> 
>> over normal I/O.
>>
>> Furthermore, we set the rebalance thread's scheduling class to BATCH,
>> which means that it will potentially receive a higher scheduling
>> latency. Making room for threads that need a low
>> schedulinglatency (e.g., interactive onces).
> 
> s/schedulinglatency/
> I know nothing about bcachefs internals, but could this also be a problem?
> The rebalance thread might not run for O(second) or so?

Thanks for the review, much appreciated. I have adjusted the commit 
message in my branch [1].

Bcachefs rebalance task is not really scheduling latency sensitive, 
unlike bcachefs' copygc task, so it is fine to run it under BATCH.

- Florian

1: 
https://github.com/Flowdalic/linux/tree/bcachefs-rebalance-set-sched-batch


Download attachment "OpenPGP_signature.asc" of type "application/pgp-signature" (619 bytes)