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Message-ID: <65d88186-7975-46ff-aef9-3b3a34f8e97a@efficios.com>
Date: Wed, 13 Mar 2024 19:24:49 -0400
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Subject: Re: [RFC PATCH 1/2] smp: Implement serialized smp_call_function APIs
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To: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: Peter Oskolkov <posk@google.com>, linux-kernel@vger.kernel.org,
 Peter Zijlstra <peterz@infradead.org>,
 "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
 Boqun Feng <boqun.feng@gmail.com>, Andrew Hunter <ahh@google.com>,
 Maged Michael <maged.michael@gmail.com>, gromer@google.com,
 Avi Kivity <avi@scylladb.com>,
 Benjamin Herrenschmidt <benh@kernel.crashing.org>,
 Paul Mackerras <paulus@samba.org>, Michael Ellerman <mpe@ellerman.id.au>
References: <20240313205622.2179659-1-mathieu.desnoyers@efficios.com>
 <20240313205622.2179659-2-mathieu.desnoyers@efficios.com>
 <CAHk-=wj5rEZFvaLgs-ZtsCX9++mFNYKox21SBfF8vrSQG4WbPA@mail.gmail.com>
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
In-Reply-To: <CAHk-=wj5rEZFvaLgs-ZtsCX9++mFNYKox21SBfF8vrSQG4WbPA@mail.gmail.com>
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On 2024-03-13 17:19, Linus Torvalds wrote:
> On Wed, 13 Mar 2024 at 13:56, Mathieu Desnoyers
> <mathieu.desnoyers@efficios.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