linux-kernel - Re: [RFC PATCH 1/2] smp: Implement serialized smp_call

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Message-ID: <65d88186-7975-46ff-aef9-3b3a34f8e97a@efficios.com>
Date: Wed, 13 Mar 2024 19:24:49 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Linus Torvalds <torvalds@...uxfoundation.org>
Cc: Peter Oskolkov <posk@...gle.com>, linux-kernel@...r.kernel.org,
 Peter Zijlstra <peterz@...radead.org>,
 "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
 Boqun Feng <boqun.feng@...il.com>, Andrew Hunter <ahh@...gle.com>,
 Maged Michael <maged.michael@...il.com>, gromer@...gle.com,
 Avi Kivity <avi@...lladb.com>,
 Benjamin Herrenschmidt <benh@...nel.crashing.org>,
 Paul Mackerras <paulus@...ba.org>, Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [RFC PATCH 1/2] smp: Implement serialized smp_call_function APIs

On 2024-03-13 17:19, Linus Torvalds wrote:
> On Wed, 13 Mar 2024 at 13:56, Mathieu Desnoyers
> <mathieu.desnoyers@...icios.com> wrote:
>>
>> Introduce serialized smp_call_function APIs to limit the number of
>> concurrent smp_call_function IPIs which can be sent to a given CPU to a
>> maximum of two: one broadcast and one specifically targeting the CPU.
> 
> So  honestly, with only one user, I think the serialization code
> should be solidly in that one user, not in kernel/smp.c.

Good point, unless other users of this show up, I could move it
into membarrier.c. But only if anyone cares enough to come up
with benchmarks justifying the added complexity.

> 
> Also, this kind of extra complexity does require numbers to argue for it.

Of course,

Thanks,

Mathieu

> 
>               Linus

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com