From: Paul Walmsley <paul@pwsan.com>
To: "Björn Töpel" <bjorn.topel@gmail.com>
Cc: linux-riscv@lists.infradead.org, Christoph Lameter <cl@linux.com>
Subject: Re: per-cpu thoughts
Date: Thu, 21 Feb 2019 17:49:13 +0000 (UTC) [thread overview]
Message-ID: <alpine.DEB.2.21.999.1902211740020.8433@utopia.booyaka.com> (raw)
In-Reply-To: <CAJ+HfNhmJq7ut2OsTvy8N8r2zeiJgBAYdUj0g-SoCso9Y-V6Gg@mail.gmail.com>
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On Thu, 21 Feb 2019, Björn Töpel wrote:
> On Thu, 21 Feb 2019 at 17:28, Paul Walmsley <paul@pwsan.com> wrote:
> >
> > On Wed, 20 Feb 2019, Björn Töpel wrote:
> >
> > > Christopher mentioned "per-cpu atomicity" in his Plumbers RISC-V HPC
> > > talk [1]. Typically, this would be for the per-cpu implementation in
> > > Linux, so I had a look at the current implementation.
> > >
> > > I noticed that RISC-V currently uses the generic one. Has there been
> > > any work on moving to a RISC-V specific impl, based on the
> > > A-extensions, similar to what aarch64 does? Would that make sense?
> >
> > Yes doing a RISC-V implementation with the AMO instructions would make
> > sense. Care to take that on?
> >
>
> Yeah, I'll take a stab at it! I guess AMO is in general favored over
> the LL/SC path, correct?
Yes. I think our current plan is to only support cores with the
A-extension in upstream Linux. Between LR/SC and atomics, the atomics
would be preferred. As Christoph wrote, using an atomic add avoids the
fail/retry risk inherent in an LR/SC sequence, and is easier to optimize
in microarchitecture.
- Paul
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next prev parent reply other threads:[~2019-02-21 17:49 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-20 19:57 per-cpu thoughts Björn Töpel
2019-02-21 15:57 ` Christopher Lameter
2019-02-21 16:28 ` Paul Walmsley
2019-02-21 17:24 ` Björn Töpel
2019-02-21 17:49 ` Paul Walmsley [this message]
2019-02-21 19:40 ` Palmer Dabbelt
2019-02-22 15:04 ` Christopher Lameter
2019-02-22 15:36 ` Nick Kossifidis
2019-02-22 15:56 ` Christopher Lameter
2019-02-22 19:47 ` Björn Töpel
2019-02-22 19:56 ` Christopher Lameter
2019-02-28 12:20 ` Paul Walmsley
2019-02-28 17:58 ` Christopher Lameter
2019-02-28 18:42 ` Paul Walmsley
2019-02-28 19:09 ` Christopher Lameter
2019-02-28 20:21 ` Paul Walmsley
2019-03-01 1:13 ` Christopher Lameter
2019-03-08 7:17 ` Björn Töpel
2019-03-11 13:22 ` Palmer Dabbelt
2019-03-11 14:48 ` Björn Töpel
2019-03-11 14:56 ` Christopher Lameter
2019-03-11 15:05 ` Björn Töpel
2019-03-11 15:26 ` Paul Walmsley
2019-03-11 16:48 ` Mark Rutland
2019-03-11 18:39 ` Paul Walmsley
2019-03-12 11:23 ` Mark Rutland
2019-03-12 16:01 ` Paul Walmsley
2019-03-12 17:34 ` Christopher Lameter
2019-03-12 4:26 ` Christopher Lameter
2019-03-12 14:21 ` Paul Walmsley
2019-03-12 17:42 ` Christopher Lameter
2019-03-12 17:59 ` Gary Guo
2019-03-13 18:58 ` Christopher Lameter
2019-03-13 20:15 ` Paul Walmsley
2019-03-22 14:51 ` Nick Kossifidis
2019-03-22 17:57 ` Christopher Lameter
2019-03-11 15:51 ` Christopher Lameter
2019-03-11 16:35 ` Björn Töpel
2019-03-12 4:22 ` Christopher Lameter
2019-02-22 19:48 ` Björn Töpel
2019-02-22 20:53 ` Nick Kossifidis
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