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
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
From: Jan Glauber <jglauber@marvell.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jan Glauber <jglauber@cavium.com>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Jayachandran Chandrasekharan Nair <jnair@marvell.com>
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
next prev parent reply other threads:[~2019-06-06 8:03 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-29 14:52 [RFC] Disable lockref on arm64 Jan Glauber
2019-04-29 14:52 ` Jan Glauber
2019-05-01 16:01 ` Will Deacon
2019-05-01 16:01 ` Will Deacon
2019-05-02 8:38 ` Jan Glauber
2019-05-02 8:38 ` Jan Glauber
2019-05-01 16:41 ` Linus Torvalds
2019-05-01 16:41 ` Linus Torvalds
2019-05-02 8:27 ` Jan Glauber
2019-05-02 8:27 ` Jan Glauber
2019-05-02 16:12 ` Linus Torvalds
2019-05-02 16:12 ` Linus Torvalds
2019-05-02 23:19 ` Jayachandran Chandrasekharan Nair
2019-05-02 23:19 ` Jayachandran Chandrasekharan Nair
2019-05-03 19:40 ` Linus Torvalds
2019-05-03 19:40 ` Linus Torvalds
2019-05-06 6:13 ` [EXT] " Jayachandran Chandrasekharan Nair
2019-05-06 6:13 ` Jayachandran Chandrasekharan Nair
2019-05-06 17:13 ` Linus Torvalds
2019-05-06 17:13 ` Linus Torvalds
2019-05-06 18:10 ` Will Deacon
2019-05-06 18:10 ` Will Deacon
2019-05-18 4:24 ` Jayachandran Chandrasekharan Nair
2019-05-18 4:24 ` Jayachandran Chandrasekharan Nair
2019-05-18 10:00 ` Ard Biesheuvel
2019-05-18 10:00 ` Ard Biesheuvel
2019-05-22 16:04 ` Will Deacon
2019-05-22 16:04 ` Will Deacon
2019-06-12 4:10 ` Jayachandran Chandrasekharan Nair
2019-06-12 4:10 ` Jayachandran Chandrasekharan Nair
2019-06-12 9:31 ` Will Deacon
2019-06-12 9:31 ` Will Deacon
2019-06-14 7:09 ` Jayachandran Chandrasekharan Nair
2019-06-14 7:09 ` Jayachandran Chandrasekharan Nair
2019-06-14 9:58 ` Will Deacon
2019-06-14 9:58 ` Will Deacon
2019-06-14 10:24 ` Ard Biesheuvel
2019-06-14 10:24 ` Ard Biesheuvel
2019-06-14 10:38 ` Will Deacon
2019-06-14 10:38 ` Will Deacon
2019-06-15 4:21 ` Kees Cook
2019-06-15 4:21 ` Kees Cook
2019-06-15 8:47 ` Ard Biesheuvel
2019-06-15 8:47 ` Ard Biesheuvel
2019-06-15 13:59 ` Kees Cook
2019-06-15 13:59 ` Kees Cook
2019-06-15 14:18 ` Ard Biesheuvel
2019-06-15 14:18 ` Ard Biesheuvel
2019-06-16 21:31 ` Kees Cook
2019-06-16 21:31 ` Kees Cook
2019-06-17 11:33 ` Ard Biesheuvel
2019-06-17 11:33 ` Ard Biesheuvel
2019-06-17 17:26 ` Will Deacon
2019-06-17 17:26 ` Will Deacon
2019-06-17 20:07 ` Jayachandran Chandrasekharan Nair
2019-06-17 20:07 ` Jayachandran Chandrasekharan Nair
2019-06-18 5:41 ` Kees Cook
2019-06-18 5:41 ` Kees Cook
2019-06-13 9:53 ` Hanjun Guo
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 13:48 ` Jan Glauber
2019-06-05 20:16 ` Linus Torvalds
2019-06-05 20:16 ` Linus Torvalds
2019-06-06 8:03 ` Jan Glauber [this message]
2019-06-06 8:03 ` Jan Glauber
2019-06-06 9:41 ` Will Deacon
2019-06-06 9:41 ` Will Deacon
2019-06-06 10:28 ` Jan Glauber
2019-06-06 10:28 ` Jan Glauber
2019-06-07 7:27 ` Jan Glauber
2019-06-07 7:27 ` Jan Glauber
2019-06-07 20:14 ` Linus Torvalds
2019-06-07 20:14 ` Linus Torvalds
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190606080317.GA10606@hc \
--to=jglauber@marvell.com \
--cc=catalin.marinas@arm.com \
--cc=jglauber@cavium.com \
--cc=jnair@marvell.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=will.deacon@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.