From: peterz@infradead.org
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Christoph Hellwig" <hch@lst.de>,
"Ingo Molnar" <mingo@kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Will Deacon" <will@kernel.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
"Jens Axboe" <axboe@kernel.dk>,
"Chris Wilson" <chris@chris-wilson.co.uk>,
"David Miller" <davem@davemloft.net>,
"Jakub Kicinski" <kuba@kernel.org>,
"Frédéric Weisbecker" <fweisbec@gmail.com>,
"Oleg Nesterov" <oleg@redhat.com>,
"Vincent Guittot" <vincent.guittot@linaro.org>
Subject: Re: [RFC][PATCH v2 08/10] smp,irq_work: Use the new irq_work API
Date: Thu, 20 Aug 2020 15:08:12 +0200 [thread overview]
Message-ID: <20200820130812.GU2674@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAHk-=wh2_pAFxa8FN95KoOseqMYPD0iX-d6ORbXxX22ixVZwBQ@mail.gmail.com>
On Wed, Aug 19, 2020 at 03:04:56PM -0700, Linus Torvalds wrote:
> On Wed, Aug 19, 2020 at 12:41 PM <peterz@infradead.org> wrote:
> >
> > I'm not sure I get the "expensive irq_work queues" argument, I fully
> > agree with you that adding the atomic op is fairly crap.
>
> There's an atomic op on the actual runing side too, because of the
> whole IRQ_WORK_PENDING thing.
>
> So you get that double hit.
>
> Maybe it doesn't matter. I just remember us being very careful to
> avoid any unnecessary atomics in the smp_call_function area, but
> admittedly I haven't worked on that code for a few years, so ..
Patch #3 trades that atomic for a full barrier. Not a massive win on
x86, but still.
next prev parent reply other threads:[~2020-08-20 13:08 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-18 10:51 [PATCH v2 00/10] smp: irq_work / smp_call_function rework Peter Zijlstra
2020-08-18 10:51 ` [PATCH v2 01/10] irq_work: Cleanup Peter Zijlstra
2020-08-18 10:51 ` [PATCH v2 02/10] smp: Cleanup smp_call_function*() Peter Zijlstra
2020-08-18 10:51 ` [PATCH v2 03/10] irq_work: Optimize irq_work_single() Peter Zijlstra
2020-08-18 10:51 ` [PATCH v2 04/10] irq_work: Unconditionally build on SMP Peter Zijlstra
2020-08-18 10:51 ` [PATCH v2 05/10] irq_work: Provide irq_work_queue_remote() Peter Zijlstra
2020-08-18 10:51 ` [RFC][PATCH v2 06/10] irq_work: Provide irq_work_queue_remote_static() Peter Zijlstra
2020-08-18 10:51 ` [RFC][PATCH v2 07/10] sched/fair: Exclude the current CPU from find_new_ilb() Peter Zijlstra
2020-08-18 10:51 ` [RFC][PATCH v2 08/10] smp,irq_work: Use the new irq_work API Peter Zijlstra
2020-08-18 16:25 ` Christoph Hellwig
2020-08-19 7:22 ` peterz
2020-08-19 18:50 ` Linus Torvalds
2020-08-19 19:41 ` peterz
2020-08-19 22:04 ` Linus Torvalds
2020-08-20 13:08 ` peterz [this message]
2020-08-20 6:20 ` Christoph Hellwig
2020-08-20 6:19 ` Christoph Hellwig
2020-08-20 13:40 ` peterz
2020-09-09 8:03 ` Christoph Hellwig
2020-08-18 10:51 ` [RFC][PATCH v2 09/10] smp: Make smp_call_function_single_async() safer Peter Zijlstra
2020-08-18 10:51 ` [RFC][PATCH v2 10/10] irq_work: Add a few comments Peter Zijlstra
2020-08-18 15:52 ` Randy Dunlap
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