From: Jan Glauber <jglauber@marvell.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
Jayachandran Chandrasekharan Nair <jnair@marvell.com>,
Jan Glauber <jglauber@cavium.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] lockref: Limit number of cmpxchg loop retries
Date: Thu, 6 Jun 2019 08:03:27 +0000 [thread overview]
Message-ID: <20190606080317.GA10606@hc> (raw)
In-Reply-To: <CAHk-=whPbMBGWiTdC3wqXMGMaCCHQ4WQh5ObB5iwa9gk-nCtzA@mail.gmail.com>
On Wed, Jun 05, 2019 at 01:16:46PM -0700, Linus Torvalds wrote:
> On Wed, Jun 5, 2019 at 6:49 AM Jan Glauber <jglauber@cavium.com> wrote:
> >
> > Add an upper bound to the loop to force the fallback to spinlocks
> > after some time. A retry value of 100 should not impact any hardware
> > that does not have this issue.
> >
> > With the retry limit the performance of an open-close testcase
> > improved between 60-70% on ThunderX2.
>
> Btw, did you do any kind of performance analysis across different
> retry limit values?
I tried 15/50/100/200/500, results were largely identical up to 100.
For SMT=4 a higher retry value might be better, but unless we can add a
sysctl value 100 looked like a good compromise to me.
--Jan
> I'm perfectly happy to just pick a random number and '100' looks fine
> to me, so this is mainly out of curiosity.
>
> Linus
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next prev parent reply other threads:[~2019-06-06 8:03 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-29 14:52 [RFC] Disable lockref on arm64 Jan Glauber
2019-05-01 16:01 ` Will Deacon
2019-05-02 8:38 ` Jan Glauber
2019-05-01 16:41 ` Linus Torvalds
2019-05-02 8:27 ` Jan Glauber
2019-05-02 16:12 ` Linus Torvalds
2019-05-02 23:19 ` Jayachandran Chandrasekharan Nair
2019-05-03 19:40 ` Linus Torvalds
2019-05-06 6:13 ` [EXT] " Jayachandran Chandrasekharan Nair
2019-05-06 17:13 ` Linus Torvalds
2019-05-06 18:10 ` Will Deacon
2019-05-18 4:24 ` Jayachandran Chandrasekharan Nair
2019-05-18 10:00 ` Ard Biesheuvel
2019-05-22 16:04 ` Will Deacon
2019-06-12 4:10 ` Jayachandran Chandrasekharan Nair
2019-06-12 9:31 ` Will Deacon
2019-06-14 7:09 ` Jayachandran Chandrasekharan Nair
2019-06-14 9:58 ` Will Deacon
2019-06-14 10:24 ` Ard Biesheuvel
2019-06-14 10:38 ` Will Deacon
2019-06-15 4:21 ` Kees Cook
2019-06-15 8:47 ` Ard Biesheuvel
2019-06-15 13:59 ` Kees Cook
2019-06-15 14:18 ` Ard Biesheuvel
2019-06-16 21:31 ` Kees Cook
2019-06-17 11:33 ` Ard Biesheuvel
2019-06-17 17:26 ` Will Deacon
2019-06-17 20:07 ` Jayachandran Chandrasekharan Nair
2019-06-18 5:41 ` Kees Cook
2019-06-13 9:53 ` Hanjun Guo
2019-06-05 13:48 ` [PATCH] lockref: Limit number of cmpxchg loop retries Jan Glauber
2019-06-05 20:16 ` Linus Torvalds
2019-06-06 8:03 ` Jan Glauber [this message]
2019-06-06 9:41 ` Will Deacon
2019-06-06 10:28 ` Jan Glauber
2019-06-07 7:27 ` Jan Glauber
2019-06-07 20:14 ` Linus Torvalds
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