linux-kernel - Re: [RFC PATCH 79/86] treewide: net: remove cond

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Date:   Wed, 08 Nov 2023 12:59:10 -0800
From:   Ankur Arora <ankur.a.arora@...cle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Ankur Arora <ankur.a.arora@...cle.com>,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        peterz@...radead.org, torvalds@...ux-foundation.org,
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        bharata@....com, raghavendra.kt@....com,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com,
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        Marek Lindner <mareklindner@...mailbox.ch>,
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        Antonio Quartulli <a@...table.cc>,
        Sven Eckelmann <sven@...fation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        "Nikolay Aleksandrov" <razor@...ckwall.org>,
        David Ahern <dsahern@...nel.org>,
        "Pablo Neira Ayuso" <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Matthieu Baerts <matttbe@...nel.org>,
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        Xin Long <lucien.xin@...il.com>,
        "Trond Myklebust" <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>,
        Jon Maloy <jmaloy@...hat.com>,
        Ying Xue <ying.xue@...driver.com>,
        Martin Schiller <ms@....tdt.de>
Subject: Re: [RFC PATCH 79/86] treewide: net: remove cond_resched()


Steven Rostedt <rostedt@...dmis.org> writes:

> On Wed, 8 Nov 2023 13:16:17 +0100
> Eric Dumazet <edumazet@...gle.com> wrote:
>
>> > Most of the uses here are in set-1 (some right after we give up a
>> > lock or enable bottom-halves, causing an explicit preemption check.)
>> >
>> > We can remove all of them.
>>
>> A patch series of 86 is not reasonable.

/me nods.

> Agreed. The removal of cond_resched() wasn't needed for the RFC, as there's
> really no comments needed once we make cond_resched obsolete.
>
> I think Ankur just wanted to send all the work for the RFC to let people
> know what he has done. I chalk that up as a Noobie mistake.
>
> Ankur, next time you may want to break things up to get RFCs for each step
> before going to the next one.

Yeah agreed. It would have made sense to break this up into changes
touching the scheduler code first, get agreement. Rinse. Repeat.

> Currently, it looks like the first thing to do is to start with Thomas's
> patch, and get the kinks out of NEED_RESCHED_LAZY, as Thomas suggested.
>
> Perhaps work on separating PREEMPT_RCU from PREEMPT.

Agree to both of those.

> Then you may need to work on handling the #ifndef PREEMPTION parts of the
> kernel.

In other words express !PREEMPTION scheduler models/things that depend
on cond_resched() etc, into Thomas' model?

> And so on. Each being a separate patch series that will affect the way the
> rest of the changes will be done.

Ack that.

> I want this change too, so I'm willing to help you out on this. If you
> didn't start it, I would have ;-)

Thanks and I really appreciate that.

--
ankur