From: Ankur Arora <ankur.a.arora@oracle.com>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: Ankur Arora <ankur.a.arora@oracle.com>,
Thomas Gleixner <tglx@linutronix.de>,
paulmck@kernel.org, linux-kernel@vger.kernel.org,
peterz@infradead.org, torvalds@linux-foundation.org,
akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de,
dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com,
juri.lelli@redhat.com, vincent.guittot@linaro.org,
willy@infradead.org, mgorman@suse.de, jpoimboe@kernel.org,
mark.rutland@arm.com, jgross@suse.com, andrew.cooper3@citrix.com,
bristot@kernel.org, mathieu.desnoyers@efficios.com,
geert@linux-m68k.org, glaubitz@physik.fu-berlin.de,
anton.ivanov@cambridgegreys.com, mattst88@gmail.com,
krypton@ulrich-teichert.org, rostedt@goodmis.org,
David.Laight@aculab.com, richard@nod.at, mjguzik@gmail.com,
jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com,
boris.ostrovsky@oracle.com, konrad.wilk@oracle.com,
rcu@vger.kernel.org
Subject: Re: [PATCH 15/30] rcu: handle quiescent states for PREEMPT_RCU=n, PREEMPT_COUNT=y
Date: Mon, 11 Mar 2024 22:23:14 -0700 [thread overview]
Message-ID: <8734swf2gt.fsf@oracle.com> (raw)
In-Reply-To: <7a26275f-7ed9-49a8-90ec-798f2f2de195@joelfernandes.org>
Joel Fernandes <joel@joelfernandes.org> writes:
> On 3/11/2024 11:16 PM, Ankur Arora wrote:
>>
>> Joel Fernandes <joel@joelfernandes.org> writes:
>>
>>> Hi, Thomas,
>>> Thanks for your reply! I replied below.
>>>
>>> On 3/11/2024 3:12 PM, Thomas Gleixner wrote:
>>>> On Mon, Mar 11 2024 at 11:25, Joel Fernandes wrote:
>>
>> [ ... ]
>>
>>>> What's wrong with the combination of PREEMPT_AUTO=y and PREEMPT_RCU=n?
>>>> Paul and me agreed long ago that this needs to be supported.
>>>
>>> There's nothing wrong with it. Its just a bit quirky (again just a point of
>>> view), that for a configuration that causes preemption (similar to
>>> CONFIG_PREEMPT=y), that PREEMPT_RCU can be disabled. After all, again with
>>> CONFIG_PREEMPT=y, PREEMPT_RCU cannot be currently disabled.
>>
>> I think the argument was that PREEMPT_RCU=y is suboptimal for certain
>> workloads, and those configurations might prefer the stronger
>> forward-progress guarantees that PREEMPT_RCU=n provides.
>>
>> See this:
>> https://lore.kernel.org/lkml/73ecce1c-d321-4579-b892-13b1e0a0620a@paulmck-laptop/T/#m6aab5a6fd5f1fd4c3dc9282ce564e64f2fa6cdc3
>>
>> and the surrounding thread.
>
> Thanks for the link. Sorry for any noise due to being late to the party. Based
> on the discussions, I concur with everyone on the goal of getting rid of
No worries. Given the unending context, easy enough to miss.
> CONFIG_PREEMPT_DYNAMIC and the various cond_resched()/might_sleep() things. I'll
> also go look harder at what else we need to get CONFIG_PREEMPT_RCU=y/n working
> with CONFIG_PREEMPT_AUTO=y.
Sounds great. Thanks.
And, please keep the review comments coming.
--
ankur
prev parent reply other threads:[~2024-03-12 5:25 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240213055554.1802415-1-ankur.a.arora@oracle.com>
[not found] ` <20240213055554.1802415-16-ankur.a.arora@oracle.com>
2024-03-10 10:03 ` [PATCH 15/30] rcu: handle quiescent states for PREEMPT_RCU=n, PREEMPT_COUNT=y Joel Fernandes
2024-03-10 18:56 ` Paul E. McKenney
2024-03-11 0:48 ` Joel Fernandes
2024-03-11 3:56 ` Paul E. McKenney
2024-03-11 15:01 ` Joel Fernandes
2024-03-11 20:51 ` Ankur Arora
2024-03-11 22:12 ` Thomas Gleixner
2024-03-11 5:18 ` Ankur Arora
2024-03-11 15:25 ` Joel Fernandes
2024-03-11 19:12 ` Thomas Gleixner
2024-03-11 19:53 ` Paul E. McKenney
2024-03-11 20:29 ` Thomas Gleixner
2024-03-12 0:01 ` Paul E. McKenney
2024-03-12 0:08 ` Joel Fernandes
2024-03-12 3:16 ` Ankur Arora
2024-03-12 3:24 ` Joel Fernandes
2024-03-12 5:23 ` Ankur Arora [this message]
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